Add some tests for the new executor system

And fix a couple of bugs picked up by said tests

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,16 @@
+---
+name: Bug report
+about: Report some misbehaviour in the mod
+
+---
+
+<!--
+## Before reporting
+ - Search for the bug both here and [on the ComputerCraft issues page](https://github.com/dan200/ComputerCraft/issues?utf8=%E2%9C%93&q=is%3Aissue+)
+ - If possible, try to reproduce on vanilla ComputerCraft. If it still occurs, [report on the ComputerCraft repo](https://github.com/dan200/ComputerCraft/issues/new) instead.
+-->
+
+## Useful information to include:
+ - Minecraft version
+ - CC: Tweaked version
+ - Detailed reproduction steps!** Sometimes I can spot a bug pretty easily, but often it's much more obscure. Anything you can give which will help reproduce it means it'll get fixed quicker.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,15 @@
+---
+name: Feature request
+about: Suggest an idea or improvement
+
+---
+
+<!--
+## Before reporting
+ - Search for the suggestion both here and [on the ComputerCraft issues page](https://github.com/dan200/ComputerCraft/issues?utf8=%E2%9C%93&q=is%3Aissue+). It's possible someone's suggested it before!
+ - Unless something is specific to CC:Tweaked, try to [suggest them on the ComputerCraft repo](https://github.com/dan200/ComputerCraft/issues/new). There's a lot more people watching it, so it allows the wider community to contribute.
+-->
+
+## Useful information to include:
+ - Explanation of how the feature/change chould work.
+ - Some rationale/use case for a feature. I'd like to keep CC:T as minimal

.github/pull_request_template.md

@@ -0,0 +1,9 @@
+<!--
+Unless this feature is specific to CC:Tweaked, try to [target the original ComputerCraft repo](https://github.com/dan200/ComputerCraft/) instead. There's a lot more people watching it, so it allows the wider community to contribute.
+-->
+
+## Useful information to include:
+ - Brief explanation of the changes you've made.
+ - Rationale of why this change has been made/reasoning behind it.
+
+The more information you can provide, the easier it is to review something now _and_ to see why a change was made, when the code needs updating in the future.

README.md

@@ -6,26 +6,42 @@ features of the mod. For a more stable experience, I recommend checking out the
 [original mod](https://github.com/dan200/ComputerCraft).
 
 ## What?
-CC: Tweaked does not aim to create a competing fork of ComputerCraft, nor am I planning to take it in in a vastly
-different direction to the original mod. In fact, CC: Tweaked aims to be a nurturing ground for various features, with
-a pull request against the original mod being the end goal.
+CC: Tweaked (or CC:T for short) does not aim to create a competing fork of ComputerCraft, nor am I planning to take it
+in in a vastly different direction to the original mod. In fact, CC:T aims to be a nurturing ground for various
+features, with a pull request against the original mod being the end goal.
 
-CC: Tweaked also includes many pull requests from the community which have not yet been merged, offering a large number
+CC:T also includes many pull requests from the community which have not yet been merged, offering a large number
 of additional bug fixes and features over the original mod.
 
+## Features
+CC: Tweaked contains the all features of the latest alpha, as well as numerous fixes, performance improvements and
+several additional features. I'd recommend checking out [the releases page](https://github.com/SquidDev-CC/CC-Tweaked/releases)
+to see the full changes, but here's a couple of the more interesting changes:
+
+ - Replace LuaJ with Cobalt.
+ - Allow running multiple computers at the same time.
+ - Websocket support in the HTTP library.
+ - Wired modems and cables act more like multiparts.
+ - Add map-like rendering for pocket computers and printed pages/books.
+ - Adds the `/computercraft` command, offering various diagnostic tools for server owners. This allows operators to
+   track which computers are hogging resources, turn on and shutdown multiple computers at once and interact with
+   computers remotely.
+ - Add full-block wired modems, allowing one to wrap non-solid peripherals (such as turtles, or chests if Plethora is
+   installed).
+
 ## Relation to CCTweaks?
-This mod has nothing to do with CCTweaks, though there is no denying the name is a throwback to it. However, I do plan
-to migrate some features of CCTweaks into CC: Tweaked.
+This mod has nothing to do with CCTweaks, though there is no denying the name is a throwback to it. That being said,
+several features have been included, such as full block modems, the Cobalt runtime and map-like rendering for pocket
+computers.
 
 ## Contributing
 Any contribution is welcome, be that using the mod, reporting bugs or contributing code. If you do wish to contribute
 code, do consider submitting it to the ComputerCraft repository instead.
 
-That being said, in order to start helping develop CC: Tweaked, you'll need to follow these steps:
+That being said, in order to start helping develop CC:T, you'll need to follow these steps:
 
  - **Clone the repository:** `git clone https://github.com/SquidDev-CC/CC-Tweaked.git && cd CC-Tweaked`
  - **Setup Forge:** `./gradlew setupDecompWorkspace`
  - **Test your changes:** `./gradlew runClient` (or run the `GradleStart` class from your IDE).
- 
-If you want to run CC: Tweaked in a normal Minecraft instance, run `./gradlew build` and copy the `.jar` from 
-`build/libs`.
+
+If you want to run CC:T in a normal Minecraft instance, run `./gradlew build` and copy the `.jar` from `build/libs`.

build.gradle

@@ -15,19 +15,20 @@ buildscript {
 }
 
 plugins {
-    id 'com.matthewprenger.cursegradle' version '1.0.9'
+    id 'com.matthewprenger.cursegradle' version '1.0.10'
 }
 
 apply plugin: 'net.minecraftforge.gradle.forge'
 apply plugin: 'org.ajoberstar.grgit'
+apply plugin: 'maven-publish'
+apply plugin: 'maven'
 
-
-version = "1.80pr1.3"
+version = "1.80pr1.8"
 group = "org.squiddev"
 archivesBaseName = "cc-tweaked"
 
 minecraft {
-    version = "1.12-14.21.1.2387"
+    version = "1.12.2-14.23.4.2749"
     runDir = "run"
     replace '${version}', project.version
 
@@ -36,11 +37,12 @@ minecraft {
     // stable_#            stables are built at the discretion of the MCP team.
     // Use non-default mappings at your own risk. they may not allways work.
     // simply re-run your setup task after changing the mappings to update your workspace.
-    mappings = "snapshot_20170629"
+    mappings = "snapshot_20180724"
     // makeObfSourceJar = false // an Srg named sources jar is made by default. uncomment this to disable.
 }
 
 repositories {
+    mavenLocal()
     maven {
         name = "JEI"
         url  = "http://dvs1.progwml6.com/files/maven"
@@ -49,17 +51,27 @@ repositories {
         name = "squiddev"
         url = "https://dl.bintray.com/squiddev/maven"
     }
+
+    ivy { artifactPattern "https://asie.pl/files/mods/Charset/LibOnly/[module]-[revision](-[classifier]).[ext]" }
 }
 
 configurations {
     shade
     compile.extendsFrom shade
+    deployerJars
 }
 
 dependencies {
-    deobfProvided "mezz.jei:jei_1.12:4.7.5.86:api"
-    runtime "mezz.jei:jei_1.12:4.7.5.86"
-    shade 'org.squiddev:Cobalt:0.3.0'
+    deobfProvided "mezz.jei:jei_1.12.2:4.8.5.159:api"
+    deobfProvided "pl.asie:Charset-Lib:0.5.4.6"
+
+    runtime "mezz.jei:jei_1.12.2:4.8.5.159"
+
+    shade 'org.squiddev:Cobalt:0.3.2-nothread'
+
+    testCompile 'junit:junit:4.11'
+
+    deployerJars "org.apache.maven.wagon:wagon-ssh:3.0.0"
 }
 
 javadoc {
@@ -124,6 +136,59 @@ curseforge {
     }
 }
 
+publishing {
+    publications {
+        mavenJava(MavenPublication) {
+            from components.java
+            artifact sourceJar
+        }
+    }
+}
+
+uploadArchives {
+    repositories {
+        if(project.hasProperty('mavenUploadUrl')) {
+            mavenDeployer {
+                configuration = configurations.deployerJars
+
+                repository(url: project.property('mavenUploadUrl')) {
+                    authentication(
+                        userName: project.property('mavenUploadUser'),
+                        privateKey: project.property('mavenUploadKey'))
+                }
+
+                pom.project {
+                    name 'CC: Tweaked'
+                    packaging 'jar'
+                    description 'A fork of ComputerCraft which aims to provide earlier access to the more experimental and in-development features of the mod.'
+                    url 'https://github.com/SquidDev-CC/CC-Tweaked'
+
+                    scm {
+                        url 'https://github.com/dan200/ComputerCraft.git'
+                    }
+
+                    issueManagement {
+                        system 'github'
+                        url 'https://github.com/dan200/ComputerCraft/issues'
+                    }
+
+                    licenses {
+                        license {
+                            name 'ComputerCraft Public License, Version 1.0'
+                            url 'https://github.com/dan200/ComputerCraft/blob/master/LICENSE'
+                            distribution 'repo'
+                        }
+                    }
+                }
+
+                pom.whenConfigured { pom ->
+                    pom.dependencies.clear()
+                }
+            }
+        }
+    }
+}
+
 gradle.projectsEvaluated {
     tasks.withType(JavaCompile) {
         options.compilerArgs << "-Xlint"
@@ -132,3 +197,9 @@ gradle.projectsEvaluated {
 
 runClient.outputs.upToDateWhen { false }
 runServer.outputs.upToDateWhen { false }
+
+test {
+    testLogging {
+        events "failed", "standardOut", "standardError"
+    }
+}

settings.gradle

@@ -0,0 +1 @@
+rootProject.name = 'cc-tweaked'

src/main/java/dan200/computercraft/ComputerCraft.java

@@ -7,23 +7,28 @@
 package dan200.computercraft;
 
 import com.google.common.base.CaseFormat;
+import com.google.common.base.Converter;
 import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
 import dan200.computercraft.api.lua.ILuaAPIFactory;
 import dan200.computercraft.api.media.IMedia;
 import dan200.computercraft.api.media.IMediaProvider;
 import dan200.computercraft.api.network.IPacketNetwork;
+import dan200.computercraft.api.network.wired.IWiredElement;
+import dan200.computercraft.api.network.wired.IWiredNode;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.IPeripheralProvider;
 import dan200.computercraft.api.permissions.ITurtlePermissionProvider;
 import dan200.computercraft.api.pocket.IPocketUpgrade;
 import dan200.computercraft.api.redstone.IBundledRedstoneProvider;
 import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.api.turtle.event.TurtleAction;
 import dan200.computercraft.core.apis.AddressPredicate;
 import dan200.computercraft.core.filesystem.ComboMount;
 import dan200.computercraft.core.filesystem.FileMount;
 import dan200.computercraft.core.filesystem.JarMount;
 import dan200.computercraft.core.terminal.Terminal;
+import dan200.computercraft.core.tracking.Tracking;
 import dan200.computercraft.shared.command.CommandComputer;
 import dan200.computercraft.shared.command.CommandComputerCraft;
 import dan200.computercraft.shared.common.DefaultBundledRedstoneProvider;
@@ -42,6 +47,7 @@ import dan200.computercraft.shared.network.ComputerCraftPacket;
 import dan200.computercraft.shared.network.PacketHandler;
 import dan200.computercraft.shared.peripheral.common.BlockCable;
 import dan200.computercraft.shared.peripheral.common.BlockPeripheral;
+import dan200.computercraft.shared.peripheral.common.BlockWiredModemFull;
 import dan200.computercraft.shared.peripheral.diskdrive.TileDiskDrive;
 import dan200.computercraft.shared.peripheral.modem.BlockAdvancedModem;
 import dan200.computercraft.shared.peripheral.modem.WirelessNetwork;
@@ -55,6 +61,8 @@ import dan200.computercraft.shared.turtle.blocks.BlockTurtle;
 import dan200.computercraft.shared.turtle.blocks.TileTurtle;
 import dan200.computercraft.shared.turtle.upgrades.*;
 import dan200.computercraft.shared.util.*;
+import dan200.computercraft.shared.wired.CapabilityWiredElement;
+import dan200.computercraft.shared.wired.WiredNode;
 import io.netty.buffer.Unpooled;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.player.EntityPlayer;
@@ -62,11 +70,13 @@ import net.minecraft.entity.player.EntityPlayerMP;
 import net.minecraft.item.ItemStack;
 import net.minecraft.network.PacketBuffer;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.tileentity.TileEntity;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.util.EnumHand;
 import net.minecraft.util.NonNullList;
 import net.minecraft.util.SoundEvent;
 import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 import net.minecraftforge.common.config.ConfigCategory;
 import net.minecraftforge.common.config.Configuration;
@@ -88,6 +98,7 @@ import java.net.MalformedURLException;
 import java.net.URISyntaxException;
 import java.net.URL;
 import java.util.*;
+import java.util.function.Function;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
 
@@ -140,6 +151,7 @@ public class ComputerCraft
     public static int advancedTurtleFuelLimit = 100000;
     public static boolean turtlesObeyBlockProtection = true;
     public static boolean turtlesCanPush = true;
+    public static EnumSet<TurtleAction> turtleDisabledActions = EnumSet.noneOf( TurtleAction.class );
 
     public static final int terminalWidth_computer = 51;
     public static final int terminalHeight_computer = 19;
@@ -172,6 +184,7 @@ public class ComputerCraft
         public static BlockTurtle turtleAdvanced;
         public static BlockCommandComputer commandComputer;
         public static BlockAdvancedModem advancedModem;
+        public static BlockWiredModemFull wiredModemFull;
     }
 
     public static class Items
@@ -222,6 +235,7 @@ public class ComputerCraft
         public static Property advancedTurtleFuelLimit;
         public static Property turtlesObeyBlockProtection;
         public static Property turtlesCanPush;
+        public static Property turtleDisabledActions;
 
         public static Property modem_range;
         public static Property modem_highAltitudeRange;
@@ -277,6 +291,18 @@ public class ComputerCraft
 
         // Load config
         Config.config = new Configuration( event.getSuggestedConfigurationFile() );
+        loadConfig();
+
+        // Setup network
+        networkEventChannel = NetworkRegistry.INSTANCE.newEventDrivenChannel( "CC" );
+        networkEventChannel.register( new PacketHandler() );
+
+        proxy.preInit();
+        turtleProxy.preInit();
+    }
+
+    public static void loadConfig()
+    {
         Config.config.load();
 
         Config.http_enable = Config.config.get( Configuration.CATEGORY_GENERAL, "http_enable", http_enable );
@@ -365,6 +391,9 @@ public class ComputerCraft
         Config.turtlesCanPush = Config.config.get( Configuration.CATEGORY_GENERAL, "turtlesCanPush", turtlesCanPush );
         Config.turtlesCanPush.setComment( "If set to true, Turtles will push entities out of the way instead of stopping if there is space to do so" );
 
+        Config.turtleDisabledActions = Config.config.get( Configuration.CATEGORY_GENERAL, "turtle_disabled_actions", new String[ 0 ] );
+        Config.turtleDisabledActions.setComment( "A list of turtle actions which are disabled." );
+
         Config.maxNotesPerTick = Config.config.get( Configuration.CATEGORY_GENERAL, "maxNotesPerTick", maxNotesPerTick );
         Config.maxNotesPerTick.setComment( "Maximum amount of notes a speaker can play at once" );
 
@@ -374,13 +403,6 @@ public class ComputerCraft
         }
 
         syncConfig();
-
-        // Setup network
-        networkEventChannel = NetworkRegistry.INSTANCE.newEventDrivenChannel( "CC" );
-        networkEventChannel.register( new PacketHandler() );
-
-        proxy.preInit();
-        turtleProxy.preInit();
     }
 
     public static void syncConfig() {
@@ -412,6 +434,20 @@ public class ComputerCraft
         turtlesObeyBlockProtection = Config.turtlesObeyBlockProtection.getBoolean();
         turtlesCanPush = Config.turtlesCanPush.getBoolean();
 
+        turtleDisabledActions.clear();
+        Converter<String, String> converter = CaseFormat.LOWER_CAMEL.converterTo( CaseFormat.UPPER_UNDERSCORE );
+        for( String value : Config.turtleDisabledActions.getStringList() )
+        {
+            try
+            {
+                turtleDisabledActions.add( TurtleAction.valueOf( converter.convert( value ) ) );
+            }
+            catch( IllegalArgumentException e )
+            {
+                ComputerCraft.log.error( "Unknown turtle action " + value );
+            }
+        }
+
         maxNotesPerTick = Math.max(1, Config.maxNotesPerTick.getInt());
 
         Config.config.save();
@@ -427,8 +463,7 @@ public class ComputerCraft
     @Mod.EventHandler
     public void onServerStarting( FMLServerStartingEvent event )
     {
-        event.registerServerCommand( new CommandComputer() );
-        event.registerServerCommand( new CommandComputerCraft() );
+        proxy.initServer( event.getServer() );
     }
 
     @Mod.EventHandler
@@ -438,6 +473,7 @@ public class ComputerCraft
         {
             ComputerCraft.serverComputerRegistry.reset();
             WirelessNetwork.resetNetworks();
+            Tracking.reset();
         }
     }
 
@@ -448,6 +484,7 @@ public class ComputerCraft
         {
             ComputerCraft.serverComputerRegistry.reset();
             WirelessNetwork.resetNetworks();
+            Tracking.reset();
         }
     }
 
@@ -471,11 +508,6 @@ public class ComputerCraft
         return proxy.getRenderFrame();
     }
 
-    public static void deleteDisplayLists( int list, int range )
-    {
-        proxy.deleteDisplayLists( list, range );
-    }
-
     public static Object getFixedWidthFontRenderer()
     {
         return proxy.getFixedWidthFontRenderer();
@@ -704,6 +736,11 @@ public class ComputerCraft
         }
     }
 
+    public static IWiredNode createWiredNodeForElement( IWiredElement element )
+    {
+        return new WiredNode( element );
+    }
+
     public static IPeripheral getPeripheralAt( World world, BlockPos pos, EnumFacing side )
     {
         // Try the handlers in order:
@@ -725,6 +762,14 @@ public class ComputerCraft
         return null;
     }
 
+    public static IWiredElement getWiredElementAt( IBlockAccess world, BlockPos pos, EnumFacing side )
+    {
+        TileEntity tile = world.getTileEntity( pos );
+        return tile != null && tile.hasCapability( CapabilityWiredElement.CAPABILITY, side )
+            ? tile.getCapability( CapabilityWiredElement.CAPABILITY, side )
+            : null;
+    }
+
     public static int getDefaultBundledRedstoneOutput( World world, BlockPos pos, EnumFacing side )
     {
         if( WorldUtil.isBlockInWorld( world, pos ) )
@@ -826,7 +871,7 @@ public class ComputerCraft
         return upgrades;
     }
 
-    public IPacketNetwork getWirelessNetwork()
+    public static IPacketNetwork getWirelessNetwork()
     {
         return WirelessNetwork.getUniversal();
     }
@@ -1080,13 +1125,18 @@ public class ComputerCraft
         turtleProxy.addAllUpgradedTurtles( list );
     }
 
-    public static void setEntityDropConsumer( Entity entity, IEntityDropConsumer consumer )
+    public static void setDropConsumer( Entity entity, Function<ItemStack, ItemStack> consumer )
     {
-        turtleProxy.setEntityDropConsumer( entity, consumer );
+        turtleProxy.setDropConsumer( entity, consumer );
     }
 
-    public static void clearEntityDropConsumer( Entity entity )
+    public static void setDropConsumer( World world, BlockPos pos, Function<ItemStack, ItemStack> consumer )
     {
-        turtleProxy.clearEntityDropConsumer( entity );
+        turtleProxy.setDropConsumer( world, pos, consumer );
+    }
+
+    public static List<ItemStack> clearDropConsumer( )
+    {
+        return turtleProxy.clearDropConsumer();
     }
 }

src/main/java/dan200/computercraft/api/ComputerCraftAPI.java

@@ -12,6 +12,8 @@ import dan200.computercraft.api.lua.ILuaAPIFactory;
 import dan200.computercraft.api.media.IMedia;
 import dan200.computercraft.api.media.IMediaProvider;
 import dan200.computercraft.api.network.IPacketNetwork;
+import dan200.computercraft.api.network.wired.IWiredElement;
+import dan200.computercraft.api.network.wired.IWiredNode;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.IPeripheralProvider;
@@ -21,6 +23,7 @@ import dan200.computercraft.api.redstone.IBundledRedstoneProvider;
 import dan200.computercraft.api.turtle.ITurtleUpgrade;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.IBlockAccess;
 import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
@@ -328,6 +331,61 @@ public final class ComputerCraftAPI
         }
     }
 
+    /**
+     * Construct a new wired node for a given wired element
+     *
+     * @param element The element to construct it for
+     * @return The element's node
+     * @see IWiredElement#getNode()
+     */
+    @Nonnull
+    public static IWiredNode createWiredNodeForElement( @Nonnull IWiredElement element )
+    {
+        findCC();
+        if( computerCraft_createWiredNodeForElement != null )
+        {
+            try
+            {
+                return (IWiredNode) computerCraft_createWiredNodeForElement.invoke( null, element );
+            }
+            catch( ReflectiveOperationException e )
+            {
+                throw new IllegalStateException( "Error creating wired node", e );
+            }
+        }
+        else
+        {
+            throw new IllegalStateException( "ComputerCraft cannot be found" );
+        }
+    }
+
+    /**
+     * Get the wired network element for a block in world
+     *
+     * @param world The world the block exists in
+     * @param pos   The position the block exists in
+     * @param side  The side to extract the network element from
+     * @return The element's node
+     * @see IWiredElement#getNode()
+     */
+    @Nullable
+    public static IWiredElement getWiredElementAt( @Nonnull IBlockAccess world, @Nonnull BlockPos pos, @Nonnull EnumFacing side )
+    {
+        findCC();
+        if( computerCraft_getWiredElementAt != null )
+        {
+            try
+            {
+                return (IWiredElement) computerCraft_getWiredElementAt.invoke( null, world, pos, side );
+            }
+            catch( ReflectiveOperationException ignored )
+            {
+            }
+        }
+        
+        return null;
+    }
+
     // The functions below here are private, and are used to interface with the non-API ComputerCraft classes.
     // Reflection is used here so you can develop your mod without decompiling ComputerCraft and including
     // it in your solution, and so your mod won't crash if ComputerCraft is installed.
@@ -374,6 +432,12 @@ public final class ComputerCraftAPI
                 computerCraft_registerAPIFactory = findCCMethod( "registerAPIFactory", new Class<?>[] {
                     ILuaAPIFactory.class
                 } );
+                computerCraft_createWiredNodeForElement = findCCMethod( "createWiredNodeForElement", new Class<?>[] {
+                    IWiredElement.class
+                } );
+                computerCraft_getWiredElementAt = findCCMethod( "getWiredElementAt", new Class<?>[]{
+                    IBlockAccess.class, BlockPos.class, EnumFacing.class
+                } );
             } catch( Exception e ) {
                 System.out.println( "ComputerCraftAPI: ComputerCraft not found." );
             } finally {
@@ -411,4 +475,6 @@ public final class ComputerCraftAPI
     private static Method computerCraft_registerPocketUpgrade = null;
     private static Method computerCraft_getWirelessNetwork = null;
     private static Method computerCraft_registerAPIFactory = null;
+    private static Method computerCraft_createWiredNodeForElement = null;
+    private static Method computerCraft_getWiredElementAt = null;
 }

src/main/java/dan200/computercraft/api/lua/ICallContext.java

@@ -0,0 +1,31 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+
+/**
+ * An interface passed to peripherals and {@link ILuaObject}s by computers or turtles, providing methods that allow the
+ * method to interact with the invoking computer.
+ */
+public interface ICallContext
+{
+    /**
+     * Queue a task to be executed on the main server thread at the beginning of next tick, but do not wait for it to
+     * complete. This should be used when you need to interact with the world in a thread-safe manner but do not care
+     * about the result or you wish to run asynchronously.
+     *
+     * When the task has finished, it will enqueue a {@code task_completed} event, which takes the task id, a success
+     * value and the return values, or an error message if it failed. If you need to wait on this event, it may be
+     * better to use {@link MethodResult#onMainThread(ILuaCallable)}.
+     *
+     * @param task The task to execute on the main thread.
+     * @return The "id" of the task. This will be the first argument to the {@code task_completed} event.
+     * @throws LuaException If the task could not be queued.
+     */
+    long issueMainThreadTask( @Nonnull ILuaTask task ) throws LuaException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaCallable.java

@@ -0,0 +1,31 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+
+/**
+ * A function which calls performs an action in a specific context (such as on the server thread) and returns a result.
+ *
+ * @see MethodResult#onMainThread(ILuaCallable)
+ * @see ILuaContext#executeMainThreadTask(ILuaTask)
+ */
+@FunctionalInterface
+public interface ILuaCallable
+{
+    /**
+     * Run the code within the specified context and return the result to continue with.
+     *
+     * @return The result of executing this function. Note that this may not be evaluated within the same context as
+     * this call is.
+     * @throws LuaException If you throw any exception from this function, a lua error will be raised with the
+     *                      same message as your exception. Use this to throw appropriate errors if the wrong
+     *                      arguments are supplied to your method.
+     */
+    @Nonnull
+    MethodResult execute() throws LuaException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaContext.java

@@ -1,6 +1,6 @@
 /*
  * This file is part of the public ComputerCraft API - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
  * For help using the API, and posting your mods, visit the forums at computercraft.info.
  */
 
@@ -13,8 +13,11 @@ import javax.annotation.Nullable;
  * An interface passed to peripherals and {@link ILuaObject}s by computers or turtles, providing methods
  * that allow the peripheral call to wait for events before returning, just like in lua. This is very useful if you need
  * to signal work to be performed on the main thread, and don't want to return until the work has been completed.
+ *
+ * This interface mostly exists for integrating with older code. One should use {@link MethodResult} instead, as this
+ * encourages an asynchronous way of interacting with Lua coroutines.
  */
-public interface ILuaContext
+public interface ILuaContext extends ICallContext
 {
     /**
      * Wait for an event to occur on the computer, suspending the thread until it arises. This method is exactly
@@ -30,8 +33,10 @@ public interface ILuaContext
      * @throws InterruptedException If the user shuts down or reboots the computer while pullEvent() is waiting for an
      *                              event, InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
+     * @deprecated Use {@link MethodResult#pullEvent(String, ILuaFunction)}
      */
     @Nonnull
+    @Deprecated
     Object[] pullEvent( @Nullable String filter ) throws LuaException, InterruptedException;
 
     /**
@@ -45,8 +50,10 @@ public interface ILuaContext
      *                              an event, InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #pullEvent(String)
+     * @deprecated Use {@link MethodResult#pullEventRaw(String, ILuaFunction)}
      */
     @Nonnull
+    @Deprecated
     Object[] pullEventRaw( @Nullable String filter ) throws InterruptedException;
 
     /**
@@ -59,8 +66,10 @@ public interface ILuaContext
      *                              InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #pullEvent(String)
+     * @deprecated Use {@link MethodResult#pullEventRaw(ILuaFunction)}
      */
     @Nonnull
+    @Deprecated
     Object[] yield( @Nullable Object[] arguments ) throws InterruptedException;
 
     /**
@@ -76,22 +85,9 @@ public interface ILuaContext
      * @throws InterruptedException If the user shuts down or reboots the computer the coroutine is suspended,
      *                              InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
+     * @deprecated Use {@link MethodResult#onMainThread(ILuaCallable)}
      */
     @Nullable
+    @Deprecated
     Object[] executeMainThreadTask( @Nonnull ILuaTask task ) throws LuaException, InterruptedException;
-
-    /**
-     * Queue a task to be executed on the main server thread at the beginning of next tick, but do not wait for it to
-     * complete. This should be used when you need to interact with the world in a thread-safe manner but do not care
-     * about the result or you wish to run asynchronously.
-     *
-     * When the task has finished, it will enqueue a {@code task_completed} event, which takes the task id, a success
-     * value and the return values, or an error message if it failed. If you need to wait on this event, it may be
-     * better to use {@link #executeMainThreadTask(ILuaTask)}.
-     *
-     * @param task The task to execute on the main thread.
-     * @return The "id" of the task. This will be the first argument to the {@code task_completed} event.
-     * @throws LuaException If the task could not be queued.
-     */
-    long issueMainThreadTask( @Nonnull ILuaTask task ) throws LuaException;
 }

src/main/java/dan200/computercraft/api/lua/ILuaContextTask.java

@@ -0,0 +1,24 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * A function which executes using a {@link ILuaContext}.
+ *
+ * Like {@link ILuaContext}, this is not intended for use in the future - it purely exists as an argument for
+ * {@link MethodResult#withLuaContext(ILuaContextTask)}.
+ */
+@FunctionalInterface
+public interface ILuaContextTask
+{
+    @Nullable
+    @Deprecated
+    Object[] execute( @Nonnull ILuaContext context ) throws LuaException, InterruptedException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaFunction.java

@@ -0,0 +1,33 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * A Lua function which consumes some values and returns a result.
+ *
+ * @see MethodResult#then(ILuaFunction)
+ * @see MethodResult#pullEvent(ILuaFunction)
+ * @see MethodResult#pullEventRaw(String)
+ */
+@FunctionalInterface
+public interface ILuaFunction
+{
+    /**
+     * Accept the values and return another method result.
+     *
+     * @param values The inputs for this function.
+     * @return The result of executing this function.
+     * @throws LuaException If you throw any exception from this function, a lua error will be raised with the
+     *                      same message as your exception. Use this to throw appropriate errors if the wrong
+     *                      arguments are supplied to your method.
+     */
+    @Nonnull
+    MethodResult call( @Nullable Object[] values ) throws LuaException;
+}

src/main/java/dan200/computercraft/api/lua/ILuaObject.java

@@ -1,6 +1,6 @@
 /*
  * This file is part of the public ComputerCraft API - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
  * For help using the API, and posting your mods, visit the forums at computercraft.info.
  */
 
@@ -41,16 +41,45 @@ public interface ILuaObject
      *                  wishes to call. The integer indicates the index into the getMethodNames() table
      *                  that corresponds to the string passed into peripheral.call()
      * @param arguments The arguments for this method. See {@link IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])}
-     *                  the possible values and conversion rules.
-     * @return An array of objects, representing the values you wish to return to the Lua program.
-     * See {@link IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])} for the valid values and
-     * conversion rules.
-     * @throws LuaException         If the task could not be queued, or if the task threw an exception.
+     *                  for the possible values and conversion rules.
+     * @return An array of objects, representing the values you wish to return to the Lua program. See
+     * {@link MethodResult#of(Object...)}  for the valid values and conversion rules.
+     * @throws LuaException         If you throw any exception from this function, a lua error will be raised with the
+     *                              same message as your exception. Use this to throw appropriate errors if the wrong
+     *                              arguments are supplied to your method.
      * @throws InterruptedException If the user shuts down or reboots the computer the coroutine is suspended,
      *                              InterruptedException will be thrown. This exception must not be caught or
-     *                              intercepted, or the computer will leak memory and end up in a broken state.w
+     *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])
+     * @deprecated Use {@link #callMethod(ICallContext, int, Object[])} instead.
      */
     @Nullable
+    @Deprecated
     Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException;
+
+    /**
+     * Called when a user calls one of the methods that this object implements. This works the same as
+     * {@link IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])}}. See that method for detailed
+     * documentation.
+     *
+     * @param context   The context of the current call.
+     * @param method    An integer identifying which of the methods from getMethodNames() the computercraft
+     *                  wishes to call. The integer indicates the index into the getMethodNames() table
+     *                  that corresponds to the string passed into peripheral.call()
+     * @param arguments The arguments for this method. See {@link IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])}
+     *                  for the possible values and conversion rules.
+     * @return The result of calling this method. Use {@link MethodResult#empty()} to return nothing or
+     * {@link MethodResult#of(Object...)} to return several values.
+     * @throws LuaException         If you throw any exception from this function, a lua error will be raised with the
+     *                              same message as your exception. Use this to throw appropriate errors if the wrong
+     *                              arguments are supplied to your method.
+     * @see IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])
+     * @see MethodResult
+     */
+    @Nonnull
+    @SuppressWarnings( { "deprecation" } )
+    default MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
+    {
+        return MethodResult.withLuaContext( lua -> callMethod( lua, method, arguments ) );
+    }
 }

src/main/java/dan200/computercraft/api/lua/LuaContextResultEvaluator.java

@@ -0,0 +1,105 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import javax.annotation.Nonnull;
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+/**
+ * Evaluates {@link MethodResult}s within a {@link ILuaContext}.
+ *
+ * @see MethodResult#evaluate(ILuaContext)
+ * @see MethodResult#withLuaContext(ILuaContextTask)
+ * @deprecated This should not be used except to interface between the two call call systems.
+ */
+@Deprecated
+class LuaContextResultEvaluator
+{
+    @Deprecated
+    public static Object[] evaluate( @Nonnull ILuaContext context, @Nonnull MethodResult future ) throws LuaException, InterruptedException
+    {
+        Deque<ILuaFunction> callbacks = null;
+        while( true )
+        {
+            if( future instanceof MethodResult.AndThen )
+            {
+                MethodResult.AndThen then = ((MethodResult.AndThen) future);
+
+                // Thens are "unwrapped", being pushed onto a stack
+                if( callbacks == null ) callbacks = new ArrayDeque<>();
+                callbacks.addLast( then.getCallback() );
+
+                future = then.getPrevious();
+                if( future == null ) throw new NullPointerException( "Null result from " + then.getCallback() );
+            }
+            else if( future instanceof MethodResult.Immediate )
+            {
+                Object[] values = ((MethodResult.Immediate) future).getResult();
+
+                // Immediate values values will attempt to call the previous "then", or return if nothing 
+                // else needs to be done.
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return values;
+
+                future = callback.call( values );
+                if( future == null ) throw new NullPointerException( "Null result from " + callback );
+            }
+            else if( future instanceof MethodResult.OnEvent )
+            {
+                MethodResult.OnEvent onEvent = (MethodResult.OnEvent) future;
+
+                // Poll for an event, and then call the previous "then" or return if nothing else needs 
+                // to be done. 
+                Object[] values = onEvent.isRaw() ? context.pullEventRaw( onEvent.getFilter() ) : context.pullEvent( onEvent.getFilter() );
+
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return values;
+
+                future = callback.call( values );
+                if( future == null ) throw new NullPointerException( "Null result from " + callback );
+            }
+            else if( future instanceof MethodResult.OnMainThread )
+            {
+                MethodResult.OnMainThread onMainThread = (MethodResult.OnMainThread) future;
+
+                // Evaluate our task on the main thread and mark it as the next future to evaluate.
+                Reference temporary = new Reference();
+                context.executeMainThreadTask( () -> {
+                    temporary.value = onMainThread.getTask().execute();
+                    return null;
+                } );
+
+                future = temporary.value;
+                if( future == null ) throw new NullPointerException( "Null result from " + onMainThread.getTask() );
+            }
+            else if( future instanceof MethodResult.WithLuaContext )
+            {
+                MethodResult.WithLuaContext withContext = (MethodResult.WithLuaContext) future;
+
+                // Run the task, and then call the previous "then" or return if nothing else
+                // needs to be done. 
+                Object[] values = withContext.getConsumer().execute( context );
+
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return values;
+                
+                future = callback.call( values );
+                if( future == null ) throw new NullPointerException( "Null result from " + callback );
+            }
+            else
+            {
+                throw new IllegalStateException( "Unknown MethodResult " + future );
+            }
+        }
+    }
+
+    private static class Reference
+    {
+        MethodResult value;
+    }
+}

src/main/java/dan200/computercraft/api/lua/MethodResult.java

@@ -0,0 +1,354 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.lua;
+
+import com.google.common.base.Preconditions;
+import com.google.common.util.concurrent.ListenableFuture;
+import dan200.computercraft.api.peripheral.IComputerAccess;
+import dan200.computercraft.api.peripheral.IPeripheral;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.Map;
+
+/**
+ * The result of calling a method, such as {@link ILuaObject#callMethod(ICallContext, int, Object[])} or
+ * {@link IPeripheral#callMethod(IComputerAccess, ICallContext, int, Object[])}.
+ *
+ * This is non-dissimilar to a promise or {@link ListenableFuture}. One can either return an immediate value through
+ * {@link #of(Object...)}, wait for an external action with {@link #onMainThread(ILuaCallable)} or {@link #pullEvent()}
+ * and then act on the result of either of those by using {@link #then(ILuaFunction)}.
+ */
+public abstract class MethodResult
+{
+    private static MethodResult empty;
+
+    MethodResult()
+    {
+    }
+
+    /**
+     * A result which returns immediately with no value.
+     *
+     * Use {@link #of(Object...)} if you need to return one or more values.
+     *
+     * @return The empty method result.
+     * @see #of(Object...)
+     */
+    @Nonnull
+    public static MethodResult empty()
+    {
+        if( empty == null ) empty = new Immediate( null );
+        return empty;
+    }
+
+    /**
+     * A result which returns several values.
+     *
+     * @param result The values to return, this may be {@code null}. {@link Number}s, {@link String}s, {@link Boolean}s,
+     *               {@link Map}s, {@link ILuaObject}s, and {@code null} be converted to their corresponding lua type.
+     *               All other types will be converted to nil.
+     * @return A result which will return these values when evaluated.
+     * @see #empty()
+     */
+    @Nonnull
+    public static MethodResult of( Object... result )
+    {
+        return result == null ? empty() : new Immediate( result );
+    }
+
+    /**
+     * Wait for an event to occur on the computer, suspending the coroutine until it arises. This method is equivalent
+     * to {@code os.pullEvent()} in Lua.
+     *
+     * Normally you'll wish to consume the event using {@link #then(ILuaFunction)}. This can be done slightly more
+     * easily with {@link #pullEvent(ILuaFunction)}.
+     *
+     * If you want to listen to a specific event, it's easier to use {@link #pullEvent(String)} rather than
+     * running until the desired event is found.
+     *
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     * @see #pullEvent(ILuaFunction)
+     * @see #pullEvent(String)
+     */
+    @Nonnull
+    public static MethodResult pullEvent()
+    {
+        return new OnEvent( false, null );
+    }
+
+    /**
+     * Wait for the specified event to occur on the computer, suspending the coroutine until it arises. This method is
+     * equivalent to {@code os.pullEvent(event)} in Lua.
+     *
+     * Normally you'll wish to consume the event using {@link #then(ILuaFunction)}. This can be done slightly more
+     * easily with {@link #pullEvent(String, ILuaFunction)}.
+     *
+     * @param filter The event name to filter on.
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     * @see #pullEvent(String, ILuaFunction)
+     * @see #pullEvent()
+     */
+    @Nonnull
+    public static MethodResult pullEvent( @Nonnull String filter )
+    {
+        Preconditions.checkNotNull( filter, "event cannot be null" );
+        return new OnEvent( false, filter );
+    }
+
+    /**
+     * Wait for an event to occur on the computer, suspending the coroutine until it arises. This method to
+     * {@link #pullEvent()} and {@link #then(ILuaFunction)}.
+     *
+     * If you want to listen to a specific event, it's easier to use {@link #pullEvent(String, ILuaFunction)} rather
+     * than running until the desired event is found.
+     *
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     * @see #pullEvent()
+     * @see #pullEvent(String, ILuaFunction)
+     */
+    @Nonnull
+    public static MethodResult pullEvent( @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( false, null ).then( callback );
+    }
+
+    /**
+     * Wait for the specified event to occur on the computer, suspending the coroutine until it arises. This method to
+     * {@link #pullEvent(String)} and {@link #then(ILuaFunction)}.
+     *
+     * @param filter   The event name to filter on.
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     * @see #pullEvent(String)
+     * @see #pullEvent(ILuaFunction)
+     */
+    @Nonnull
+    public static MethodResult pullEvent( @Nullable String filter, @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( false, filter ).then( callback );
+    }
+
+    /**
+     * The same as {@link #pullEvent()}, except {@code terminated} events are also passed to the callback, instead of
+     * throwing an error. Only use this if you want to prevent program termination, which is not recommended.
+     *
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw()
+    {
+        return new OnEvent( true, null );
+    }
+
+    /**
+     * The same as {@link #pullEvent(String)}, except {@code terminated} events are also passed to the callback, instead
+     * of throwing an error. Only use this if you want to prevent program termination, which is not recommended.
+     *
+     * @param filter The event name to filter on.
+     * @return The constructed method result. This evaluates to the name of the event that occurred, and any event
+     * parameters.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw( @Nonnull String filter )
+    {
+        return new OnEvent( true, filter );
+    }
+
+    /**
+     * The same as {@link #pullEvent(ILuaFunction)}, except {@code terminated} events are also passed to the callback,
+     * instead of throwing an error. Only use this if you want to prevent program termination, which is not recommended.
+     *
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw( @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( true, null ).then( callback );
+    }
+
+    /**
+     * The same as {@link #pullEvent(String, ILuaFunction)}, except {@code terminated} events are also passed to the
+     * callback, instead of throwing an error. Only use this if you want to prevent program termination, which is not
+     * recommended.
+     *
+     * @param filter   The event name to filter on.
+     * @param callback The function to call when the event is received.
+     * @return The constructed method result. This evaluates to the result of the {@code callback}.
+     */
+    @Nonnull
+    public static MethodResult pullEventRaw( @Nullable String filter, @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnEvent( true, filter ).then( callback );
+    }
+
+    /**
+     * Queue a task to be executed on the main server thread at the beginning of next tick, waiting for it to complete.
+     * This should be used when you need to interact with the world in a thread-safe manner.
+     *
+     * @param callback The task to execute on the server thread.
+     * @return The constructed method result, which evaluates to the result of the {@code callback}.
+     */
+    @Nonnull
+    public static MethodResult onMainThread( @Nonnull ILuaCallable callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new OnMainThread( callback );
+    }
+
+    /**
+     * Consume the result of this {@link MethodResult} and return another result.
+     *
+     * Note this does NOT modify the current method result, rather returning a new (wrapped) one. You must return the
+     * result of this call if you wish to use it.
+     *
+     * @param callback The function which consumes the provided values.
+     * @return The constructed method result.
+     */
+    @Nonnull
+    public final MethodResult then( @Nonnull ILuaFunction callback )
+    {
+        Preconditions.checkNotNull( callback, "callback cannot be null" );
+        return new AndThen( this, callback );
+    }
+
+    /**
+     * Execute a blocking task within a {@link ILuaContext} and return its result.
+     *
+     * @param consumer The task to execute with the provided Lua context.
+     * @return The constructed method result.
+     * @see #evaluate(ILuaContext)
+     * @deprecated This should not be used except to interface between the two call systems.
+     */
+    @Deprecated
+    public static MethodResult withLuaContext( @Nonnull ILuaContextTask consumer )
+    {
+        Preconditions.checkNotNull( consumer, "consumer cannot be null" );
+        return new WithLuaContext( consumer );
+    }
+
+    /**
+     * Evaluate this result task using {@link ILuaContext} and return its result.
+     *
+     * @param context The context to execute with.
+     * @return The resulting values.
+     * @throws LuaException         If an error was thrown while executing one of the methods within this future.
+     * @throws InterruptedException If the user shuts down or reboots the computer while the coroutine is suspended.
+     * @see #withLuaContext(ILuaContextTask)
+     * @deprecated This should not be used except to interface between the two call systems.
+     */
+    @Deprecated
+    public final Object[] evaluate( @Nonnull ILuaContext context ) throws LuaException, InterruptedException
+    {
+        return LuaContextResultEvaluator.evaluate( context, this );
+    }
+
+    public static class Immediate extends MethodResult
+    {
+        @Nullable
+        private final Object[] values;
+
+        @Nullable
+        private Immediate( Object[] values )
+        {
+            this.values = values;
+        }
+
+        public Object[] getResult()
+        {
+            return values;
+        }
+    }
+
+    public static class OnEvent extends MethodResult
+    {
+        private final boolean raw;
+        private final String filter;
+
+        private OnEvent( boolean raw, String filter )
+        {
+            this.raw = raw;
+            this.filter = filter;
+        }
+
+        public boolean isRaw()
+        {
+            return raw;
+        }
+
+        @Nullable
+        public String getFilter()
+        {
+            return filter;
+        }
+    }
+
+    public static class OnMainThread extends MethodResult
+    {
+        private final ILuaCallable task;
+
+        public OnMainThread( ILuaCallable task )
+        {
+            this.task = task;
+        }
+
+        @Nonnull
+        public ILuaCallable getTask()
+        {
+            return task;
+        }
+    }
+
+    public static class AndThen extends MethodResult
+    {
+        private final MethodResult previous;
+        private final ILuaFunction callback;
+
+        private AndThen( MethodResult previous, ILuaFunction callback )
+        {
+            this.previous = previous;
+            this.callback = callback;
+        }
+
+        @Nonnull
+        public MethodResult getPrevious()
+        {
+            return previous;
+        }
+
+        @Nonnull
+        public ILuaFunction getCallback()
+        {
+            return callback;
+        }
+    }
+
+    public static class WithLuaContext extends MethodResult
+    {
+        private final ILuaContextTask consumer;
+
+        private WithLuaContext( ILuaContextTask consumer )
+        {
+            this.consumer = consumer;
+        }
+
+        @Nonnull
+        public ILuaContextTask getConsumer()
+        {
+            return consumer;
+        }
+    }
+}

src/main/java/dan200/computercraft/api/network/wired/IWiredElement.java

@@ -0,0 +1,29 @@
+package dan200.computercraft.api.network.wired;
+
+import dan200.computercraft.api.ComputerCraftAPI;
+
+import javax.annotation.Nonnull;
+
+/**
+ * An object which may be part of a wired network.
+ *
+ * Elements should construct a node using {@link ComputerCraftAPI#createWiredNodeForElement(IWiredElement)}. This acts
+ * as a proxy for all network objects. Whilst the node may change networks, an element's node should remain constant
+ * for its lifespan.
+ *
+ * Elements are generally tied to a block or tile entity in world. In such as case, one should provide the
+ * {@link IWiredElement} capability for the appropriate sides.
+ */
+public interface IWiredElement extends IWiredSender
+{
+    /**
+     * Called when objects on the network change. This may occur when network nodes are added or removed, or when
+     * peripherals change.
+     *
+     * @param change The change which occurred.
+     * @see IWiredNetworkChange
+     */
+    default void networkChanged( @Nonnull IWiredNetworkChange change )
+    {
+    }
+}

src/main/java/dan200/computercraft/api/network/wired/IWiredNetwork.java

@@ -0,0 +1,80 @@
+package dan200.computercraft.api.network.wired;
+
+import dan200.computercraft.api.peripheral.IPeripheral;
+
+import javax.annotation.Nonnull;
+import java.util.Map;
+
+/**
+ * A wired network is composed of one of more {@link IWiredNode}s, a set of connections between them, and a series
+ * of peripherals.
+ *
+ * Networks from a connected graph. This means there is some path between all nodes on the network. Further more, if
+ * there is some path between two nodes then they must be on the same network. {@link IWiredNetwork} will automatically
+ * handle the merging and splitting of networks (and thus changing of available nodes and peripherals) as connections
+ * change.
+ *
+ * This does mean one can not rely on the network remaining consistent between subsequent operations. Consequently,
+ * it is generally preferred to use the methods provided by {@link IWiredNode}.
+ *
+ * @see IWiredNode#getNetwork()
+ */
+public interface IWiredNetwork
+{
+    /**
+     * Create a connection between two nodes.
+     *
+     * This should only be used on the server thread.
+     *
+     * @param left  The first node to connect
+     * @param right The second node to connect
+     * @return {@code true} if a connection was created or {@code false} if the connection already exists.
+     * @throws IllegalStateException    If neither node is on the network.
+     * @throws IllegalArgumentException If {@code left} and {@code right} are equal.
+     * @see IWiredNode#connectTo(IWiredNode)
+     * @see IWiredNetwork#connect(IWiredNode, IWiredNode)
+     */
+    boolean connect( @Nonnull IWiredNode left, @Nonnull IWiredNode right );
+
+    /**
+     * Destroy a connection between this node and another.
+     *
+     * This should only be used on the server thread.
+     *
+     * @param left  The first node in the connection.
+     * @param right The second node in the connection.
+     * @return {@code true} if a connection was destroyed or {@code false} if no connection exists.
+     * @throws IllegalArgumentException If either node is not on the network.
+     * @throws IllegalArgumentException If {@code left} and {@code right} are equal.
+     * @see IWiredNode#disconnectFrom(IWiredNode)
+     * @see IWiredNetwork#connect(IWiredNode, IWiredNode)
+     */
+    boolean disconnect( @Nonnull IWiredNode left, @Nonnull IWiredNode right );
+
+    /**
+     * Sever all connections this node has, removing it from this network.
+     *
+     * This should only be used on the server thread. You should only call this on nodes
+     * that your network element owns.
+     *
+     * @param node The node to remove
+     * @return Whether this node was removed from the network. One cannot remove a node from a network where it is the
+     * only element.
+     * @throws IllegalArgumentException If the node is not in the network.
+     * @see IWiredNode#remove()
+     */
+    boolean remove( @Nonnull IWiredNode node );
+
+    /**
+     * Update the peripherals a node provides.
+     *
+     * This should only be used on the server thread. You should only call this on nodes
+     * that your network element owns.
+     *
+     * @param node        The node to attach peripherals for.
+     * @param peripherals The new peripherals for this node.
+     * @throws IllegalArgumentException If the node is not in the network.
+     * @see IWiredNode#updatePeripherals(Map)
+     */
+    void updatePeripherals( @Nonnull IWiredNode node, @Nonnull Map<String, IPeripheral> peripherals );
+}

src/main/java/dan200/computercraft/api/network/wired/IWiredNetworkChange.java

@@ -0,0 +1,32 @@
+package dan200.computercraft.api.network.wired;
+
+import dan200.computercraft.api.peripheral.IPeripheral;
+
+import javax.annotation.Nonnull;
+import java.util.Map;
+
+/**
+ * Represents a change to the objects on a wired network.
+ *
+ * @see IWiredElement#networkChanged(IWiredNetworkChange)
+ */
+public interface IWiredNetworkChange
+{
+    /**
+     * A set of peripherals which have been removed. Note that there may be entries with the same name
+     * in the added and removed set, but with a different peripheral.
+     *
+     * @return The set of removed peripherals.
+     */
+    @Nonnull
+    Map<String, IPeripheral> peripheralsRemoved();
+
+    /**
+     * A set of peripherals which have been added. Note that there may be entries with the same name
+     * in the added and removed set, but with a different peripheral.
+     *
+     * @return The set of added peripherals.
+     */
+    @Nonnull
+    Map<String, IPeripheral> peripheralsAdded();
+}

src/main/java/dan200/computercraft/api/network/wired/IWiredNode.java

@@ -0,0 +1,103 @@
+package dan200.computercraft.api.network.wired;
+
+import dan200.computercraft.api.network.IPacketNetwork;
+import dan200.computercraft.api.peripheral.IPeripheral;
+
+import javax.annotation.Nonnull;
+import java.util.Map;
+
+/**
+ * Wired nodes act as a layer between {@link IWiredElement}s and {@link IWiredNetwork}s.
+ *
+ * Firstly, a node acts as a packet network, capable of sending and receiving modem messages to connected nodes. These
+ * methods may be safely used on any thread.
+ *
+ * When sending a packet, the system will attempt to find the shortest path between the two nodes based on their
+ * element's position. Note that packet senders and receivers can have different locations from their associated
+ * element: the distance between the two will be added to the total packet's distance.
+ *
+ * Wired nodes also provide several convenience methods for interacting with a wired network. These should only ever
+ * be used on the main server thread.
+ */
+public interface IWiredNode extends IPacketNetwork
+{
+    /**
+     * The associated element for this network node.
+     *
+     * @return This node's element.
+     */
+    @Nonnull
+    IWiredElement getElement();
+
+    /**
+     * The network this node is currently connected to. Note that this may change
+     * after any network operation, so it should not be cached.
+     *
+     * This should only be used on the server thread.
+     *
+     * @return This node's network.
+     */
+    @Nonnull
+    IWiredNetwork getNetwork();
+
+    /**
+     * Create a connection from this node to another.
+     *
+     * This should only be used on the server thread.
+     *
+     * @param node The other node to connect to.
+     * @return {@code true} if a connection was created or {@code false} if the connection already exists.
+     * @see IWiredNetwork#connect(IWiredNode, IWiredNode)
+     * @see IWiredNode#disconnectFrom(IWiredNode)
+     */
+    default boolean connectTo( @Nonnull IWiredNode node )
+    {
+        return getNetwork().connect( this, node );
+    }
+
+    /**
+     * Destroy a connection between this node and another.
+     *
+     * This should only be used on the server thread.
+     *
+     * @param node The other node to disconnect from.
+     * @return {@code true} if a connection was destroyed or {@code false} if no connection exists.
+     * @throws IllegalArgumentException If {@code node} is not on the same network.
+     * @see IWiredNetwork#disconnect(IWiredNode, IWiredNode)
+     * @see IWiredNode#connectTo(IWiredNode)
+     */
+    default boolean disconnectFrom( @Nonnull IWiredNode node )
+    {
+        return getNetwork().disconnect( this, node );
+    }
+
+    /**
+     * Sever all connections this node has, removing it from this network.
+     *
+     * This should only be used on the server thread. You should only call this on nodes
+     * that your network element owns.
+     *
+     * @return Whether this node was removed from the network. One cannot remove a node from a network where it is the
+     * only element.
+     * @throws IllegalArgumentException If the node is not in the network.
+     * @see IWiredNetwork#remove(IWiredNode)
+     */
+    default boolean remove()
+    {
+        return getNetwork().remove( this );
+    }
+
+    /**
+     * Mark this node's peripherals as having changed.
+     *
+     * This should only be used on the server thread. You should only call this on nodes
+     * that your network element owns.
+     *
+     * @param peripherals The new peripherals for this node.
+     * @see IWiredNetwork#updatePeripherals(IWiredNode, Map)
+     */
+    default void updatePeripherals( @Nonnull Map<String, IPeripheral> peripherals )
+    {
+        getNetwork().updatePeripherals( this, peripherals );
+    }
+}

src/main/java/dan200/computercraft/api/network/wired/IWiredSender.java

@@ -0,0 +1,25 @@
+package dan200.computercraft.api.network.wired;
+
+import dan200.computercraft.api.network.IPacketSender;
+
+import javax.annotation.Nonnull;
+
+/**
+ * An object on a {@link IWiredNetwork} capable of sending packets.
+ *
+ * Unlike a regular {@link IPacketSender}, this must be associated with the node you are attempting to
+ * to send the packet from.
+ */
+public interface IWiredSender extends IPacketSender
+{
+    /**
+     * The node in the network representing this object.
+     *
+     * This should be used as a proxy for the main network. One should send packets
+     * and register receivers through this object.
+     *
+     * @return The node for this element.
+     */
+    @Nonnull
+    IWiredNode getNode();
+}

src/main/java/dan200/computercraft/api/network/wired/package-info.java

@@ -0,0 +1,10 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+@API( owner="ComputerCraft", provides="ComputerCraft|API|Network|Wired", apiVersion="${version}" )
+package dan200.computercraft.api.network.wired;
+
+import net.minecraftforge.fml.common.API;

src/main/java/dan200/computercraft/api/peripheral/IComputerAccess.java

@@ -13,6 +13,8 @@ import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
+import java.util.Collections;
+import java.util.Map;
 
 /**
  * The interface passed to peripherals by computers or turtles, providing methods
@@ -154,4 +156,33 @@ public interface IComputerAccess
      */
     @Nonnull
     String getAttachmentName();
+
+    /**
+     * Get a set of peripherals that this computer access can "see", along with their attachment name.
+     *
+     * This may include other peripherals on the wired network or peripherals on other sides of the computer.
+     *
+     * @return All reachable peripherals
+     * @see #getAttachmentName()
+     * @see #getAvailablePeripheral(String)
+     */
+    @Nonnull
+    default Map<String, IPeripheral> getAvailablePeripherals()
+    {
+        return Collections.emptyMap();
+    }
+
+    /**
+     * Get a reachable peripheral with the given attachement name. This is a equivalent to
+     * {@link #getAvailablePeripherals()}{@code .get(name)}, though may be more performant.
+     *
+     * @param name The peripheral's attached name
+     * @return The reachable peripheral, or {@code null} if none can be found.
+     * @see #getAvailablePeripherals()
+     */
+    @Nullable
+    default IPeripheral getAvailablePeripheral( @Nonnull String name )
+    {
+        return null;
+    }
 }

src/main/java/dan200/computercraft/api/peripheral/IPeripheral.java

@@ -1,13 +1,15 @@
 /*
  * This file is part of the public ComputerCraft API - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * Copyright Daniel Ratcliffe, 2011-2018. This API may be redistributed unmodified and in full only.
  * For help using the API, and posting your mods, visit the forums at computercraft.info.
  */
 
 package dan200.computercraft.api.peripheral;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -70,10 +72,46 @@ public interface IPeripheral
      *                              InterruptedException will be thrown. This exception must not be caught or
      *                              intercepted, or the computer will leak memory and end up in a broken state.
      * @see #getMethodNames
+     * @deprecated Use {@link #callMethod(IComputerAccess, ICallContext, int, Object[])} instead.
      */
     @Nullable
+    @Deprecated
     Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException;
 
+    /**
+     * This is called when a lua program on an attached computer calls {@code peripheral.call()} with
+     * one of the methods exposed by {@link #getMethodNames()}.
+     *
+     * Be aware that this will be called from the ComputerCraft Lua thread, and must be thread-safe
+     * when interacting with Minecraft objects.
+     *
+     * @param computer  The interface to the computer that is making the call. Remember that multiple
+     *                  computers can be attached to a peripheral at once.
+     * @param context   The context of the current call.
+     * @param method    An integer identifying which of the methods from getMethodNames() the computercraft
+     *                  wishes to call. The integer indicates the index into the getMethodNames() table
+     *                  that corresponds to the string passed into peripheral.call()
+     * @param arguments An array of objects, representing the arguments passed into {@code peripheral.call()}.<br>
+     *                  Lua values of type "string" will be represented by Object type String.<br>
+     *                  Lua values of type "number" will be represented by Object type Double.<br>
+     *                  Lua values of type "boolean" will be represented by Object type Boolean.<br>
+     *                  Lua values of type "table" will be represented by Object type Map.<br>
+     *                  Lua values of any other type will be represented by a null object.<br>
+     *                  This array will be empty if no arguments are passed.
+     * @return The result of calling this method. Use {@link MethodResult#empty()} to return nothing or
+     * {@link MethodResult#of(Object...)} to return several values.
+     * @throws LuaException If you throw any exception from this function, a lua error will be raised with the
+     *                      same message as your exception. Use this to throw appropriate errors if the wrong
+     *                      arguments are supplied to your method.
+     * @see #getMethodNames
+     */
+    @Nonnull
+    @SuppressWarnings({ "deprecation" })
+    default MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
+    {
+        return MethodResult.withLuaContext( lua -> callMethod( computer, lua, method, arguments ) );
+    }
+
     /**
      * Is called when canAttachToSide has returned true, and a computer is attaching to the peripheral.
      *
@@ -114,6 +152,18 @@ public interface IPeripheral
     {
     }
 
+    /**
+     * Get the object that this peripheral provides methods for. This will generally be the tile entity
+     * or block, but may be an inventory, entity, etc...
+     *
+     * @return The object this peripheral targets
+     */
+    @Nonnull
+    default Object getTarget()
+    {
+        return this;
+    }
+
     /**
      * Determine whether this peripheral is equivalent to another one.
      *

src/main/java/dan200/computercraft/api/turtle/ITurtleAccess.java

@@ -6,8 +6,10 @@
 
 package dan200.computercraft.api.turtle;
 
+import com.mojang.authlib.GameProfile;
 import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import net.minecraft.inventory.IInventory;
 import net.minecraft.nbt.NBTTagCompound;
@@ -135,6 +137,14 @@ public interface ITurtleAccess
      */
     int getColour();
 
+    /**
+     * Get the player who owns this turtle, namely whoever placed it.
+     *
+     * @return This turtle's owner.
+     */
+    @Nonnull
+    GameProfile getOwningPlayer();
+
     /**
      * Get the inventory of this turtle
      *
@@ -148,7 +158,7 @@ public interface ITurtleAccess
      * Get the inventory of this turtle as an {@link IItemHandlerModifiable}.
      *
      * @return This turtle's inventory
-     * @see #getInventory() 
+     * @see #getInventory()
      * @see IItemHandlerModifiable
      * @see net.minecraftforge.items.CapabilityItemHandler#ITEM_HANDLER_CAPABILITY
      */
@@ -229,10 +239,30 @@ public interface ITurtleAccess
      *                                       intercepted, or the computer will leak memory and end up in a broken state.
      * @see ITurtleCommand
      * @see ILuaContext#pullEvent(String)
+     * @deprecated Use {@link #executeCommand(ITurtleCommand)} instead.
      */
     @Nonnull
+    @Deprecated
     Object[] executeCommand( @Nonnull ILuaContext context, @Nonnull ITurtleCommand command ) throws LuaException, InterruptedException;
 
+    /**
+     * Adds a custom command to the turtles command queue. Unlike peripheral methods, these custom commands will be
+     * executed on the main thread, so are guaranteed to be able to access Minecraft objects safely, and will be queued
+     * up with the turtles standard movement and tool commands.
+     *
+     * An issued command will return an unique integer, which will be supplied as a parameter to a "turtle_response"
+     * event issued to the turtle after the command has completed. Look at the Lua source code for "rom/apis/turtle" for
+     * how to build a Lua wrapper around this functionality.
+     *
+     * @param command An object which will execute the custom command when its point in the queue is reached
+     * @return The constructed method result. This evaluates to the result of the provided {@code command}.
+     * @throws UnsupportedOperationException When attempting to execute a command on the client side.
+     * @see ITurtleCommand
+     * @see MethodResult#pullEvent(String)
+     */
+    @Nonnull
+    MethodResult executeCommand( @Nonnull ITurtleCommand command );
+
     /**
      * Start playing a specific animation. This will prevent other turtle commands from executing until
      * it is finished.

src/main/java/dan200/computercraft/api/turtle/ITurtleUpgrade.java

@@ -8,11 +8,15 @@ package dan200.computercraft.api.turtle;
 
 import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.api.turtle.event.TurtleAttackEvent;
+import dan200.computercraft.api.turtle.event.TurtleBlockEvent;
 import net.minecraft.client.renderer.block.model.IBakedModel;
 import net.minecraft.client.renderer.block.model.ModelResourceLocation;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.EnumFacing;
 import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.event.entity.player.AttackEntityEvent;
+import net.minecraftforge.event.world.BlockEvent;
 import net.minecraftforge.fml.relauncher.Side;
 import net.minecraftforge.fml.relauncher.SideOnly;
 import org.apache.commons.lang3.tuple.Pair;
@@ -100,6 +104,9 @@ public interface ITurtleUpgrade
      * Will only be called for Tool turtle. Called when turtle.dig() or turtle.attack() is called
      * by the turtle, and the tool is required to do some work.
      *
+     * Conforming implementations should fire {@link BlockEvent.BreakEvent} and {@link TurtleBlockEvent.Dig}for digging,
+     * {@link AttackEntityEvent} and {@link TurtleAttackEvent} for attacking.
+     *
      * @param turtle    Access to the turtle that the tool resides on.
      * @param side      Which side of the turtle (left or right) the tool resides on.
      * @param verb      Which action (dig or attack) the turtle is being called on to perform.
@@ -126,7 +133,7 @@ public interface ITurtleUpgrade
      * @return The model that you wish to be used to render your upgrade, and a transformation to apply to it. Returning
      * a transformation of {@code null} has the same effect as the identify matrix.
      */
-    @SideOnly(Side.CLIENT)
+    @SideOnly( Side.CLIENT )
     @Nonnull
     Pair<IBakedModel, Matrix4f> getModel( @Nullable ITurtleAccess turtle, @Nonnull TurtleSide side );
 

src/main/java/dan200/computercraft/api/turtle/event/TurtleAction.java

@@ -0,0 +1,84 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.turtle.event;
+
+/**
+ * A basic action that a turtle may perform, as accessed by the {@code turtle} API.
+ *
+ * @see TurtleActionEvent
+ */
+public enum TurtleAction
+{
+    /**
+     * A turtle moves to a new position.
+     *
+     * @see TurtleBlockEvent.Move
+     */
+    MOVE,
+
+    /**
+     * A turtle turns in a specific direction.
+     */
+    TURN,
+
+    /**
+     * A turtle attempts to dig a block.
+     *
+     * @see TurtleBlockEvent.Dig
+     */
+    DIG,
+
+    /**
+     * A turtle attempts to place a block or item in the world.
+     *
+     * @see TurtleBlockEvent.Place
+     */
+    PLACE,
+
+    /**
+     * A turtle attempts to attack an entity.
+     *
+     * @see TurtleActionEvent
+     */
+    ATTACK,
+
+    /**
+     * Drop an item into an inventory/the world.
+     *
+     * @see TurtleInventoryEvent.Drop
+     */
+    DROP,
+
+    /**
+     * Suck an item from an inventory or the world.
+     *
+     * @see TurtleInventoryEvent.Suck
+     */
+    SUCK,
+
+    /**
+     * Refuel the turtle's fuel levels.
+     */
+    REFUEL,
+
+    /**
+     * Equip or unequip an item.
+     */
+    EQUIP,
+
+    /**
+     * Inspect a block in world
+     *
+     * @see TurtleBlockEvent.Inspect
+     */
+    INSPECT,
+
+    /**
+     * Gather metdata about an item in the turtle's inventory.
+     */
+    INSPECT_ITEM,
+}

src/main/java/dan200/computercraft/api/turtle/event/TurtleActionEvent.java

@@ -0,0 +1,76 @@
+package dan200.computercraft.api.turtle.event;
+
+import com.google.common.base.Preconditions;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+import dan200.computercraft.api.turtle.TurtleCommandResult;
+import net.minecraftforge.fml.common.eventhandler.Cancelable;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * An event fired when a turtle is performing a known action.
+ */
+@Cancelable
+public class TurtleActionEvent extends TurtleEvent
+{
+    private final TurtleAction action;
+    private String failureMessage;
+
+    public TurtleActionEvent( @Nonnull ITurtleAccess turtle, @Nonnull TurtleAction action )
+    {
+        super( turtle );
+
+        Preconditions.checkNotNull( action, "action cannot be null" );
+        this.action = action;
+    }
+
+    public TurtleAction getAction()
+    {
+        return action;
+    }
+
+    /**
+     * Sets the cancellation state of this action.
+     *
+     * If {@code cancel} is {@code true}, this action will not be carried out.
+     *
+     * @param cancel The new canceled value.
+     * @see TurtleCommandResult#failure()
+     * @deprecated Use {@link #setCanceled(boolean, String)} instead.
+     */
+    @Override
+    @Deprecated
+    public void setCanceled( boolean cancel )
+    {
+        setCanceled( cancel, null );
+    }
+
+    /**
+     * Set the cancellation state of this action, setting a failure message if required.
+     *
+     * If {@code cancel} is {@code true}, this action will not be carried out.
+     *
+     * @param cancel         The new canceled value.
+     * @param failureMessage The message to return to the user explaining the failure.
+     * @see TurtleCommandResult#failure(String)
+     */
+    public void setCanceled( boolean cancel, @Nullable String failureMessage )
+    {
+        super.setCanceled( cancel );
+        this.failureMessage = cancel ? failureMessage : null;
+    }
+
+    /**
+     * Get the message with which this will fail.
+     *
+     * @return The failure message.
+     * @see TurtleCommandResult#failure()
+     * @see #setCanceled(boolean, String)
+     */
+    @Nullable
+    public String getFailureMessage()
+    {
+        return failureMessage;
+    }
+}

src/main/java/dan200/computercraft/api/turtle/event/TurtleAttackEvent.java

@@ -0,0 +1,80 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.turtle.event;
+
+import com.google.common.base.Preconditions;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.api.turtle.TurtleSide;
+import dan200.computercraft.api.turtle.TurtleVerb;
+import net.minecraft.entity.Entity;
+import net.minecraft.util.EnumFacing;
+import net.minecraftforge.common.util.FakePlayer;
+import net.minecraftforge.event.entity.player.AttackEntityEvent;
+
+import javax.annotation.Nonnull;
+
+/**
+ * Fired when a turtle attempts to attack an entity.
+ *
+ * This must be fired by {@link ITurtleUpgrade#useTool(ITurtleAccess, TurtleSide, TurtleVerb, EnumFacing)},
+ * as the base {@code turtle.attack()} command does not fire it.
+ *
+ * Note that such commands should also fire {@link AttackEntityEvent}, so you do not need to listen to both.
+ *
+ * @see TurtleAction#ATTACK
+ */
+public class TurtleAttackEvent extends TurtlePlayerEvent
+{
+    private final Entity target;
+    private final ITurtleUpgrade upgrade;
+    private final TurtleSide side;
+
+    public TurtleAttackEvent( @Nonnull ITurtleAccess turtle, @Nonnull FakePlayer player, @Nonnull Entity target, @Nonnull ITurtleUpgrade upgrade, @Nonnull TurtleSide side )
+    {
+        super( turtle, TurtleAction.ATTACK, player );
+        Preconditions.checkNotNull( target, "target cannot be null" );
+        Preconditions.checkNotNull( upgrade, "upgrade cannot be null" );
+        Preconditions.checkNotNull( side, "side cannot be null" );
+        this.target = target;
+        this.upgrade = upgrade;
+        this.side = side;
+    }
+
+    /**
+     * Get the entity being attacked by this turtle.
+     *
+     * @return The entity being attacked.
+     */
+    @Nonnull
+    public Entity getTarget()
+    {
+        return target;
+    }
+
+    /**
+     * Get the upgrade responsible for attacking.
+     *
+     * @return The upgrade responsible for attacking.
+     */
+    @Nonnull
+    public ITurtleUpgrade getUpgrade()
+    {
+        return upgrade;
+    }
+
+    /**
+     * Get the side the attacking upgrade is on.
+     *
+     * @return The upgrade's side.
+     */
+    @Nonnull
+    public TurtleSide getSide()
+    {
+        return side;
+    }
+}

src/main/java/dan200/computercraft/api/turtle/event/TurtleBlockEvent.java

@@ -0,0 +1,241 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.turtle.event;
+
+import com.google.common.base.Preconditions;
+import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.peripheral.IComputerAccess;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.api.turtle.TurtleSide;
+import dan200.computercraft.api.turtle.TurtleVerb;
+import net.minecraft.block.state.IBlockState;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.EnumFacing;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
+import net.minecraftforge.common.util.FakePlayer;
+import net.minecraftforge.event.world.BlockEvent;
+import net.minecraftforge.fml.common.eventhandler.Cancelable;
+
+import javax.annotation.Nonnull;
+import java.util.Map;
+
+/**
+ * A general event for when a turtle interacts with a block or region.
+ *
+ * You should generally listen to one of the sub-events instead, cancelling them where
+ * appropriate.
+ *
+ * Note that you are not guaranteed to receive this event, if it has been cancelled by other
+ * mechanisms, such as block protection systems.
+ *
+ * Be aware that some events (such as {@link TurtleInventoryEvent}) do not necessarily interact
+ * with a block, simply objects within that block space.
+ */
+@Cancelable
+public abstract class TurtleBlockEvent extends TurtlePlayerEvent
+{
+    private final World world;
+    private final BlockPos pos;
+
+    protected TurtleBlockEvent( @Nonnull ITurtleAccess turtle, @Nonnull TurtleAction action, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos )
+    {
+        super( turtle, action, player );
+
+        Preconditions.checkNotNull( world, "world cannot be null" );
+        Preconditions.checkNotNull( pos, "pos cannot be null" );
+        this.world = world;
+        this.pos = pos;
+    }
+
+    /**
+     * Get the world the turtle is interacting in.
+     *
+     * @return The world the turtle is interacting in.
+     */
+    public World getWorld()
+    {
+        return world;
+    }
+
+    /**
+     * Get the position the turtle is interacting with. Note that this is different
+     * to {@link ITurtleAccess#getPosition()}.
+     *
+     * @return The position the turtle is interacting with.
+     */
+    public BlockPos getPos()
+    {
+        return pos;
+    }
+
+    /**
+     * Fired when a turtle attempts to dig a block.
+     *
+     * This must be fired by {@link ITurtleUpgrade#useTool(ITurtleAccess, TurtleSide, TurtleVerb, EnumFacing)},
+     * as the base {@code turtle.dig()} command does not fire it.
+     *
+     * Note that such commands should also fire {@link BlockEvent.BreakEvent}, so you do not need to listen to both.
+     *
+     * @see TurtleAction#DIG
+     */
+    @Cancelable
+    public static class Dig extends TurtleBlockEvent
+    {
+        private final IBlockState block;
+        private final ITurtleUpgrade upgrade;
+        private final TurtleSide side;
+
+        public Dig( @Nonnull ITurtleAccess turtle, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos, @Nonnull IBlockState block, @Nonnull ITurtleUpgrade upgrade, @Nonnull TurtleSide side )
+        {
+            super( turtle, TurtleAction.DIG, player, world, pos );
+
+            Preconditions.checkNotNull( block, "block cannot be null" );
+            Preconditions.checkNotNull( upgrade, "upgrade cannot be null" );
+            Preconditions.checkNotNull( side, "side cannot be null" );
+            this.block = block;
+            this.upgrade = upgrade;
+            this.side = side;
+        }
+
+        /**
+         * Get the block which is about to be broken.
+         *
+         * @return The block which is going to be broken.
+         */
+        @Nonnull
+        public IBlockState getBlock()
+        {
+            return block;
+        }
+
+        /**
+         * Get the upgrade doing the digging
+         *
+         * @return The upgrade doing the digging.
+         */
+        @Nonnull
+        public ITurtleUpgrade getUpgrade()
+        {
+            return upgrade;
+        }
+
+        /**
+         * Get the side the upgrade doing the digging is on.
+         *
+         * @return The upgrade's side.
+         */
+        @Nonnull
+        public TurtleSide getSide()
+        {
+            return side;
+        }
+    }
+
+    /**
+     * Fired when a turtle attempts to move into a block.
+     *
+     * @see TurtleAction#MOVE
+     */
+    @Cancelable
+    public static class Move extends TurtleBlockEvent
+    {
+        public Move( @Nonnull ITurtleAccess turtle, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos )
+        {
+            super( turtle, TurtleAction.MOVE, player, world, pos );
+        }
+    }
+
+    /**
+     * Fired when a turtle attempts to place a block in the world.
+     *
+     * @see TurtleAction#PLACE
+     */
+    @Cancelable
+    public static class Place extends TurtleBlockEvent
+    {
+        private final ItemStack stack;
+
+        public Place( @Nonnull ITurtleAccess turtle, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos, @Nonnull ItemStack stack )
+        {
+            super( turtle, TurtleAction.PLACE, player, world, pos );
+
+            Preconditions.checkNotNull( stack, "stack cannot be null" );
+            this.stack = stack;
+        }
+
+        /**
+         * Get the item stack that will be placed. This should not be modified.
+         *
+         * @return The item stack to be placed.
+         */
+        @Nonnull
+        public ItemStack getStack()
+        {
+            return stack;
+        }
+    }
+
+    /**
+     * Fired when a turtle gathers data on a block in world.
+     *
+     * You may prevent blocks being inspected, or add additional information to the result.
+     *
+     * @see TurtleAction#INSPECT
+     */
+    @Cancelable
+    public static class Inspect extends TurtleBlockEvent
+    {
+        private final IBlockState state;
+        private final Map<String, Object> data;
+
+        public Inspect( @Nonnull ITurtleAccess turtle, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos, @Nonnull IBlockState state, @Nonnull Map<String, Object> data )
+        {
+            super( turtle, TurtleAction.INSPECT, player, world, pos );
+
+            Preconditions.checkNotNull( state, "state cannot be null" );
+            Preconditions.checkNotNull( data, "data cannot be null" );
+            this.data = data;
+            this.state = state;
+        }
+
+        /**
+         * Get the block state which is being inspected.
+         *
+         * @return The inspected block state.
+         */
+        @Nonnull
+        public IBlockState getState()
+        {
+            return state;
+        }
+
+        /**
+         * Get the "inspection data" from this block, which will be returned to the user.
+         *
+         * @return This block's inspection data.
+         */
+        @Nonnull
+        public Map<String, Object> getData()
+        {
+            return data;
+        }
+
+        /**
+         * Add new information to the inspection result. Note this will override fields with the same name.
+         *
+         * @param newData The data to add. Note all values should be convertable to Lua (see
+         *                {@link dan200.computercraft.api.peripheral.IPeripheral#callMethod(IComputerAccess, ILuaContext, int, Object[])}).
+         */
+        public void addData( @Nonnull Map<String, ?> newData )
+        {
+            Preconditions.checkNotNull( newData, "newData cannot be null" );
+            data.putAll( newData );
+        }
+    }
+}

src/main/java/dan200/computercraft/api/turtle/event/TurtleEvent.java

@@ -0,0 +1,43 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.turtle.event;
+
+import com.google.common.base.Preconditions;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+import net.minecraftforge.fml.common.eventhandler.Event;
+
+import javax.annotation.Nonnull;
+
+/**
+ * A base class for all events concerning a turtle. This will only ever constructed and fired on the server side,
+ * so sever specific methods on {@link ITurtleAccess} are safe to use.
+ *
+ * You should generally not need to subscribe to this event, preferring one of the more specific classes.
+ *
+ * @see TurtleActionEvent
+ */
+public abstract class TurtleEvent extends Event
+{
+    private final ITurtleAccess turtle;
+
+    protected TurtleEvent( @Nonnull ITurtleAccess turtle )
+    {
+        Preconditions.checkNotNull( turtle, "turtle cannot be null" );
+        this.turtle = turtle;
+    }
+
+    /**
+     * Get the turtle which is performing this action.
+     *
+     * @return The access for this turtle.
+     */
+    @Nonnull
+    public ITurtleAccess getTurtle()
+    {
+        return turtle;
+    }
+}

src/main/java/dan200/computercraft/api/turtle/event/TurtleInventoryEvent.java

@@ -0,0 +1,84 @@
+package dan200.computercraft.api.turtle.event;
+
+import com.google.common.base.Preconditions;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.World;
+import net.minecraftforge.common.util.FakePlayer;
+import net.minecraftforge.fml.common.eventhandler.Cancelable;
+import net.minecraftforge.items.IItemHandler;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * Fired when a turtle attempts to interact with an inventory.
+ */
+@Cancelable
+public abstract class TurtleInventoryEvent extends TurtleBlockEvent
+{
+    private final IItemHandler handler;
+
+    protected TurtleInventoryEvent( @Nonnull ITurtleAccess turtle, @Nonnull TurtleAction action, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos, @Nullable IItemHandler handler )
+    {
+        super( turtle, action, player, world, pos );
+        this.handler = handler;
+    }
+
+    /**
+     * Get the inventory being interacted with
+     *
+     * @return The inventory being interacted with, {@code null} if the item will be dropped to/sucked from the world.
+     */
+    @Nullable
+    public IItemHandler getItemHandler()
+    {
+        return handler;
+    }
+
+    /**
+     * Fired when a turtle attempts to suck from an inventory.
+     *
+     * @see TurtleAction#SUCK
+     */
+    @Cancelable
+    public static class Suck extends TurtleInventoryEvent
+    {
+        public Suck( @Nonnull ITurtleAccess turtle, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos, @Nullable IItemHandler handler )
+        {
+            super( turtle, TurtleAction.SUCK, player, world, pos, handler );
+        }
+    }
+
+    /**
+     * Fired when a turtle attempts to drop an item into an inventory.
+     *
+     * @see TurtleAction#DROP
+     */
+    @Cancelable
+    public static class Drop extends TurtleInventoryEvent
+    {
+        private final ItemStack stack;
+
+        public Drop( @Nonnull ITurtleAccess turtle, @Nonnull FakePlayer player, @Nonnull World world, @Nonnull BlockPos pos, @Nullable IItemHandler handler, @Nonnull ItemStack stack )
+        {
+            super( turtle, TurtleAction.DROP, player, world, pos, handler );
+
+            Preconditions.checkNotNull( stack, "stack cannot be null" );
+            this.stack = stack;
+        }
+
+        /**
+         * The item which will be inserted into the inventory/dropped on the ground.
+         *
+         * Note that this is a copy of the original stack, and so should not be modified, as that will have no effect.
+         *
+         * @return The item stack which will be dropped.
+         */
+        public ItemStack getStack()
+        {
+            return stack.copy();
+        }
+    }
+}

src/main/java/dan200/computercraft/api/turtle/event/TurtlePlayerEvent.java

@@ -0,0 +1,44 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+package dan200.computercraft.api.turtle.event;
+
+import com.google.common.base.Preconditions;
+import dan200.computercraft.api.turtle.ITurtleAccess;
+import net.minecraftforge.common.util.FakePlayer;
+
+import javax.annotation.Nonnull;
+
+/**
+ * An action done by a turtle which is normally done by a player.
+ *
+ * {@link #getPlayer()} may be used to modify the player's attributes or perform permission checks.
+ */
+public abstract class TurtlePlayerEvent extends TurtleActionEvent
+{
+    private final FakePlayer player;
+
+    protected TurtlePlayerEvent( @Nonnull ITurtleAccess turtle, @Nonnull TurtleAction action, @Nonnull FakePlayer player )
+    {
+        super( turtle, action );
+
+        Preconditions.checkNotNull( player, "player cannot be null" );
+        this.player = player;
+    }
+
+    /**
+     * A fake player, representing this turtle.
+     *
+     * This may be used for triggering permission checks.
+     *
+     * @return A {@link FakePlayer} representing this turtle.
+     */
+    @Nonnull
+    public FakePlayer getPlayer()
+    {
+        return player;
+    }
+}

src/main/java/dan200/computercraft/api/turtle/event/package-info.java

@@ -0,0 +1,10 @@
+/*
+ * This file is part of the public ComputerCraft API - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2017. This API may be redistributed unmodified and in full only.
+ * For help using the API, and posting your mods, visit the forums at computercraft.info.
+ */
+
+@API(owner = "ComputerCraft", provides = "ComputerCraft|API|Turtle|Event", apiVersion = "${version}")
+package dan200.computercraft.api.turtle.event;
+
+import net.minecraftforge.fml.common.API;

src/main/java/dan200/computercraft/client/gui/GuiPrintout.java

@@ -6,25 +6,19 @@
 
 package dan200.computercraft.client.gui;
 
-import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.core.terminal.TextBuffer;
 import dan200.computercraft.shared.media.inventory.ContainerHeldItem;
 import dan200.computercraft.shared.media.items.ItemPrintout;
-import dan200.computercraft.shared.util.Palette;
 import net.minecraft.client.gui.inventory.GuiContainer;
 import net.minecraft.client.renderer.GlStateManager;
-import net.minecraft.util.ResourceLocation;
 import org.lwjgl.input.Mouse;
 
 import java.io.IOException;
 
+import static dan200.computercraft.client.render.PrintoutRenderer.*;
+
 public class GuiPrintout extends GuiContainer
 {
-    private static final ResourceLocation background = new ResourceLocation( "computercraft", "textures/gui/printout.png" );
-    
-    private static final int xSize = 172;
-    private static final int ySize = 209;
-    
     private final boolean m_book;
     private final int m_pages;
     private final TextBuffer[] m_text;
@@ -34,23 +28,18 @@ public class GuiPrintout extends GuiContainer
     public GuiPrintout( ContainerHeldItem container )
     {
         super( container );
-        m_book = (ItemPrintout.getType( container.getStack() ) == ItemPrintout.Type.Book);
 
         String[] text = ItemPrintout.getText( container.getStack() );
         m_text = new TextBuffer[ text.length ];
-        for( int i=0; i<m_text.length; ++i )
-        {
-            m_text[i] = new TextBuffer( text[i] );
-        }
+        for( int i = 0; i < m_text.length; ++i ) m_text[ i ] = new TextBuffer( text[ i ] );
+
         String[] colours = ItemPrintout.getColours( container.getStack() );
         m_colours = new TextBuffer[ colours.length ];
-        for( int i=0; i<m_colours.length; ++i )
-        {
-            m_colours[i] = new TextBuffer( colours[i] );
-        }
+        for( int i = 0; i < m_colours.length; ++i ) m_colours[ i ] = new TextBuffer( colours[ i ] );
 
-        m_pages = Math.max( m_text.length / ItemPrintout.LINES_PER_PAGE, 1 );
         m_page = 0;
+        m_pages = Math.max( m_text.length / ItemPrintout.LINES_PER_PAGE, 1 );
+        m_book = ItemPrintout.getType( container.getStack() ) == ItemPrintout.Type.Book;
     }
 
     @Override
@@ -78,25 +67,19 @@ public class GuiPrintout extends GuiContainer
     }
 
     @Override
-    protected void keyTyped(char c, int k) throws IOException
+    protected void keyTyped( char c, int k ) throws IOException
     {
         super.keyTyped( c, k );
 
         if( k == 205 )
         {
             // Right
-            if( m_page < m_pages - 1 )
-            {
-                m_page = m_page + 1;
-            }
+            if( m_page < m_pages - 1 ) m_page++;
         }
         else if( k == 203 )
         {
-             // Left
-            if( m_page > 0 )
-            {
-                m_page = m_page - 1;
-            }
+            // Left
+            if( m_page > 0 ) m_page--;
         }
     }
 
@@ -106,21 +89,15 @@ public class GuiPrintout extends GuiContainer
         super.handleMouseInput();
 
         int mouseWheelChange = Mouse.getEventDWheel();
-        if (mouseWheelChange < 0)
+        if( mouseWheelChange < 0 )
         {
             // Up
-            if( m_page < m_pages - 1 )
-            {
-                m_page = m_page + 1;
-            }
+            if( m_page < m_pages - 1 ) m_page++;
         }
-        else if (mouseWheelChange > 0) 
+        else if( mouseWheelChange > 0 )
         {
             // Down
-            if( m_page > 0 )
-            {
-                m_page = m_page - 1;
-            }
+            if( m_page > 0 ) m_page--;
         }
     }
 
@@ -135,78 +112,20 @@ public class GuiPrintout extends GuiContainer
     }
 
     @Override
-    public void drawScreen(int mouseX, int mouseY, float f)
+    public void drawScreen( int mouseX, int mouseY, float f )
     {
         // Draw background
+        zLevel = zLevel - 1;
         drawDefaultBackground();
-        
+        zLevel = zLevel + 1;
+
         // Draw the printout
         GlStateManager.color( 1.0f, 1.0f, 1.0f, 1.0f );
-        this.mc.getTextureManager().bindTexture( background );
-        
-        int startY = (height - ySize) / 2;
-        //int startX = (width - xSize) / 2 - (m_page * 8);
-        int startX = (width - (xSize + (m_pages - 1)*8)) / 2;
-        
-        if( m_book )
-        {
-            // Border
-            drawTexturedModalRect( startX - 8, startY - 8, xSize + 48, 0, 12, ySize + 24);
-            drawTexturedModalRect( startX + xSize + (m_pages - 1)*8 - 4, startY - 8, xSize + 48 + 12, 0, 12, ySize + 24);
-            
-            drawTexturedModalRect( startX, startY - 8, 0, ySize, xSize, 12);
-            drawTexturedModalRect( startX, startY + ySize - 4, 0, ySize + 12, xSize, 12);
-            for( int n=1; n<m_pages; ++n )
-            {
-                drawTexturedModalRect( startX + xSize + (n-1)*8, startY - 8, 0, ySize, 8, 12);
-                drawTexturedModalRect( startX + xSize + (n-1)*8, startY + ySize - 4, 0, ySize + 12, 8, 12);
-            }
-        }
-            
-        // Left half
-        if( m_page == 0 )
-        {            
-            drawTexturedModalRect( startX, startY, 24, 0, xSize / 2, ySize);
-            drawTexturedModalRect( startX, startY, 0, 0, 12, ySize);
-        }
-        else
-        {
-            drawTexturedModalRect( startX, startY, 0, 0, 12, ySize);
-            for( int n=1; n<m_page; ++n )
-            {
-                drawTexturedModalRect( startX + n*8, startY, 12, 0, 12, ySize);                
-            }
-            drawTexturedModalRect( startX + m_page*8, startY, 24, 0, xSize / 2, ySize);
-        }
-        
-        // Right half
-        if( m_page == (m_pages - 1) )
-        {
-            drawTexturedModalRect( startX + m_page*8 + xSize/2, startY, 24 + xSize / 2, 0, xSize / 2, ySize);
-            drawTexturedModalRect( startX + m_page*8 + (xSize - 12), startY, 24 + xSize + 12, 0, 12, ySize);
-        }
-        else 
-        {
-            drawTexturedModalRect( startX + (m_pages - 1)*8 + (xSize - 12), startY, 24 + xSize + 12, 0, 12, ySize);
-            for( int n=m_pages-2; n>=m_page; --n )
-            {
-                drawTexturedModalRect( startX + n*8 + (xSize - 12), startY, 24 + xSize, 0, 12, ySize);
-            }
-            drawTexturedModalRect( startX + m_page*8 + xSize/2, startY, 24 + xSize / 2, 0, xSize / 2, ySize);
-        }
 
-        // Draw the text
-        FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer)ComputerCraft.getFixedWidthFontRenderer();
-        int x = startX + m_page * 8 + 13;
-        int y = startY + 11;
-        for( int line=0; line<ItemPrintout.LINES_PER_PAGE; ++line )
-        {
-            int lineIdx = ItemPrintout.LINES_PER_PAGE * m_page + line;
-            if( lineIdx >= 0 && lineIdx < m_text.length )
-            {
-                fontRenderer.drawString( m_text[lineIdx], x, y, m_colours[lineIdx], null, 0, 0, false, Palette.DEFAULT );
-            }
-            y = y + FixedWidthFontRenderer.FONT_HEIGHT;
-        }
+        int startY = (height - Y_SIZE) / 2;
+        int startX = (width - X_SIZE) / 2;
+
+        drawBorder( startX, startY, zLevel, m_page, m_pages, m_book );
+        drawText( startX + X_TEXT_MARGIN, startY + Y_TEXT_MARGIN, ItemPrintout.LINES_PER_PAGE * m_page, m_text, m_colours );
     }
 }

src/main/java/dan200/computercraft/client/proxy/CCTurtleProxyClient.java

@@ -20,6 +20,7 @@ import net.minecraft.client.renderer.block.model.IBakedModel;
 import net.minecraft.client.renderer.block.model.ModelBakery;
 import net.minecraft.client.renderer.block.model.ModelResourceLocation;
 import net.minecraft.client.renderer.color.IItemColor;
+import net.minecraft.client.renderer.texture.TextureMap;
 import net.minecraft.client.renderer.vertex.DefaultVertexFormats;
 import net.minecraft.client.resources.IResourceManager;
 import net.minecraft.client.resources.SimpleReloadableResourceManager;
@@ -115,8 +116,23 @@ public class CCTurtleProxyClient extends CCTurtleProxyCommon
         MinecraftForge.EVENT_BUS.register( handlers );
     }
 
-    public class ForgeHandlers
+    public static class ForgeHandlers
     {
+        private static final String[] TURTLE_UPGRADES = {
+            "turtle_modem_off_left",
+            "turtle_modem_on_left",
+            "turtle_modem_off_right",
+            "turtle_modem_on_right",
+            "turtle_crafting_table_left",
+            "turtle_crafting_table_right",
+            "advanced_turtle_modem_off_left",
+            "advanced_turtle_modem_on_left",
+            "advanced_turtle_modem_off_right",
+            "advanced_turtle_modem_on_right",
+            "turtle_speaker_upgrade_left",
+            "turtle_speaker_upgrade_right",
+        };
+
         private TurtleSmartItemModel m_turtleSmartItemModel;
 
         public ForgeHandlers()
@@ -142,24 +158,27 @@ public class CCTurtleProxyClient extends CCTurtleProxyCommon
         @SubscribeEvent
         public void onTextureStitchEvent( TextureStitchEvent.Pre event )
         {
-            event.getMap().registerSprite( new ResourceLocation( "computercraft", "blocks/crafty_upgrade" ) );
+            // Load all textures for upgrades
+            TextureMap map = event.getMap();
+            for( String upgrade : TURTLE_UPGRADES )
+            {
+                IModel model = ModelLoaderRegistry.getModelOrMissing( new ResourceLocation( "computercraft", "block/" + upgrade ) );
+                for( ResourceLocation texture : model.getTextures() )
+                {
+                    map.registerSprite( texture );
+                }
+            }
         }
 
         @SubscribeEvent
         public void onModelBakeEvent( ModelBakeEvent event )
         {
-            loadModel( event, "turtle_modem_off_left" );
-            loadModel( event, "turtle_modem_on_left" );
-            loadModel( event, "turtle_modem_off_right" );
-            loadModel( event, "turtle_modem_on_right" );
-            loadModel( event, "turtle_crafting_table_left" );
-            loadModel( event, "turtle_crafting_table_right" );
-            loadModel( event, "advanced_turtle_modem_off_left" );
-            loadModel( event, "advanced_turtle_modem_on_left" );
-            loadModel( event, "advanced_turtle_modem_off_right" );
-            loadModel( event, "advanced_turtle_modem_on_right" );
-            loadModel( event, "turtle_speaker_upgrade_left" );
-            loadModel( event, "turtle_speaker_upgrade_right" );
+            // Load all upgrade models
+            for( String upgrade : TURTLE_UPGRADES )
+            {
+                loadModel( event, upgrade );
+            }
+
             loadSmartModel( event, "turtle_dynamic", m_turtleSmartItemModel );
         }
 
@@ -191,7 +210,7 @@ public class CCTurtleProxyClient extends CCTurtleProxyCommon
     private static class TurtleItemColour implements IItemColor
     {
         @Override
-        public int getColorFromItemstack( @Nonnull ItemStack stack, int tintIndex )
+        public int colorMultiplier( @Nonnull ItemStack stack, int tintIndex )
         {
             if( tintIndex == 0 )
             {

src/main/java/dan200/computercraft/client/proxy/ComputerCraftProxyClient.java

@@ -9,6 +9,7 @@ package dan200.computercraft.client.proxy;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.client.gui.*;
 import dan200.computercraft.client.render.ItemPocketRenderer;
+import dan200.computercraft.client.render.ItemPrintoutRenderer;
 import dan200.computercraft.client.render.RenderOverlayCable;
 import dan200.computercraft.client.render.TileEntityCableRenderer;
 import dan200.computercraft.client.render.TileEntityMonitorRenderer;
@@ -25,6 +26,7 @@ import dan200.computercraft.shared.media.items.ItemPrintout;
 import dan200.computercraft.shared.network.ComputerCraftPacket;
 import dan200.computercraft.shared.peripheral.diskdrive.TileDiskDrive;
 import dan200.computercraft.shared.peripheral.modem.TileCable;
+import dan200.computercraft.shared.peripheral.monitor.ClientMonitor;
 import dan200.computercraft.shared.peripheral.monitor.TileMonitor;
 import dan200.computercraft.shared.peripheral.printer.TilePrinter;
 import dan200.computercraft.shared.pocket.inventory.ContainerPocketComputer;
@@ -33,9 +35,10 @@ import dan200.computercraft.shared.proxy.ComputerCraftProxyCommon;
 import dan200.computercraft.shared.turtle.blocks.TileTurtle;
 import dan200.computercraft.shared.turtle.entity.TurtleVisionCamera;
 import dan200.computercraft.shared.util.Colour;
+import gnu.trove.map.hash.TIntIntHashMap;
 import net.minecraft.block.Block;
 import net.minecraft.client.Minecraft;
-import net.minecraft.client.renderer.GlStateManager;
+import net.minecraft.client.gui.GuiNewChat;
 import net.minecraft.client.renderer.ItemMeshDefinition;
 import net.minecraft.client.renderer.block.model.ModelBakery;
 import net.minecraft.client.renderer.block.model.ModelResourceLocation;
@@ -50,6 +53,7 @@ import net.minecraft.util.IThreadListener;
 import net.minecraft.util.ResourceLocation;
 import net.minecraft.util.SoundEvent;
 import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.text.ITextComponent;
 import net.minecraft.world.World;
 import net.minecraftforge.client.event.ModelRegistryEvent;
 import net.minecraftforge.client.event.RenderGameOverlayEvent;
@@ -57,6 +61,7 @@ import net.minecraftforge.client.event.RenderHandEvent;
 import net.minecraftforge.client.event.RenderPlayerEvent;
 import net.minecraftforge.client.model.ModelLoader;
 import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.event.world.WorldEvent;
 import net.minecraftforge.fml.client.registry.ClientRegistry;
 import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 import net.minecraftforge.fml.common.gameevent.TickEvent;
@@ -70,6 +75,8 @@ import java.util.List;
 
 public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
 {
+    private static TIntIntHashMap lastCounts = new TIntIntHashMap();
+
     private long m_tick;
     private long m_renderFrame;
     private FixedWidthFontRenderer m_fixedWidthFontRenderer;
@@ -115,6 +122,7 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
         registerItemModel( ComputerCraft.Blocks.commandComputer, "command_computer" );
         registerItemModel( ComputerCraft.Blocks.advancedModem, "advanced_modem" );
         registerItemModel( ComputerCraft.Blocks.peripheral, 5, "speaker" );
+        registerItemModel( ComputerCraft.Blocks.wiredModemFull, "wired_modem_full" );
 
         registerItemModel( ComputerCraft.Items.disk, "disk" );
         registerItemModel( ComputerCraft.Items.diskExpanded, "disk_expanded" );
@@ -296,12 +304,6 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
         return m_renderFrame;
     }
 
-    @Override
-    public void deleteDisplayLists( int list, int range )
-    {
-        GlStateManager.glDeleteLists( list, range );
-    }
-
     @Override
     public Object getFixedWidthFontRenderer()
     {
@@ -388,6 +390,7 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
             case ComputerCraftPacket.ComputerTerminalChanged:
             case ComputerCraftPacket.ComputerDeleted:
             case ComputerCraftPacket.PlayRecord:
+            case ComputerCraftPacket.PostChat:
             {
                 // Packet from Server to Client
                 IThreadListener listener = Minecraft.getMinecraft();
@@ -454,6 +457,36 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
                 {
                     mc.world.playRecord( pos, null );
                 }
+                break;
+            }
+            case ComputerCraftPacket.PostChat:
+            {
+                /*
+                  This allows us to send delete chat messages of the same "category" as the previous one.
+                  It's used by the various /computercraft commands to avoid filling the chat with repetitive
+                  messages.
+                 */
+
+                int id = packet.m_dataInt[0];
+                ITextComponent[] components = new ITextComponent[packet.m_dataString.length];
+                for( int i = 0; i < packet.m_dataString.length; i++ )
+                {
+                    components[i] = ITextComponent.Serializer.jsonToComponent( packet.m_dataString[i] );
+                }
+
+                GuiNewChat chat = Minecraft.getMinecraft().ingameGUI.getChatGUI();
+
+                // Keep track of how many lines we wrote last time, deleting any extra ones.
+                int lastCount = lastCounts.get( id );
+                for( int i = components.length; i < lastCount; i++ ) chat.deleteChatLine( i + id );
+                lastCounts.put( id, components.length );
+
+                // Add new lines
+                for( int i = 0; i < components.length; i++ )
+                {
+                    chat.printChatMessageWithOptionalDeletion( components[i], id + i );
+                }
+                break;
             }
 
         }
@@ -465,6 +498,7 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
         MinecraftForge.EVENT_BUS.register( handlers );
         MinecraftForge.EVENT_BUS.register( new RenderOverlayCable() );
         MinecraftForge.EVENT_BUS.register( new ItemPocketRenderer() );
+        MinecraftForge.EVENT_BUS.register( new ItemPrintoutRenderer() );
     }
 
     public class ForgeHandlers
@@ -551,6 +585,15 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
                 m_renderFrame++;
             }
         }
+
+        @SubscribeEvent
+        public void onWorldUnload( WorldEvent.Unload event )
+        {
+            if( event.getWorld().isRemote )
+            {
+                ClientMonitor.destroyAll();
+            }
+        }
     }
 
     @SideOnly(Side.CLIENT)
@@ -564,7 +607,7 @@ public class ComputerCraftProxyClient extends ComputerCraftProxyCommon
         }
 
         @Override
-        public int getColorFromItemstack( @Nonnull ItemStack stack, int layer )
+        public int colorMultiplier( @Nonnull ItemStack stack, int layer )
         {
             return layer == 0 ? 0xFFFFFF : disk.getColour( stack );
         }

src/main/java/dan200/computercraft/client/render/ItemPrintoutRenderer.java

@@ -0,0 +1,197 @@
+package dan200.computercraft.client.render;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.shared.media.items.ItemPrintout;
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.GlStateManager;
+import net.minecraft.client.renderer.ItemRenderer;
+import net.minecraft.entity.player.EntityPlayer;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.EnumHand;
+import net.minecraft.util.EnumHandSide;
+import net.minecraft.util.math.MathHelper;
+import net.minecraftforge.client.event.RenderItemInFrameEvent;
+import net.minecraftforge.client.event.RenderSpecificHandEvent;
+import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
+
+import static dan200.computercraft.client.gui.FixedWidthFontRenderer.FONT_HEIGHT;
+import static dan200.computercraft.client.gui.FixedWidthFontRenderer.FONT_WIDTH;
+import static dan200.computercraft.client.render.PrintoutRenderer.*;
+import static dan200.computercraft.shared.media.items.ItemPrintout.LINES_PER_PAGE;
+import static dan200.computercraft.shared.media.items.ItemPrintout.LINE_MAX_LENGTH;
+
+public class ItemPrintoutRenderer
+{
+    @SubscribeEvent
+    public void onRenderInHand( RenderSpecificHandEvent event )
+    {
+        ItemStack stack = event.getItemStack();
+        if( stack.getItem() != ComputerCraft.Items.printout ) return;
+
+        event.setCanceled( true );
+
+        EntityPlayer player = Minecraft.getMinecraft().player;
+
+        GlStateManager.pushMatrix();
+        if( event.getHand() == EnumHand.MAIN_HAND && player.getHeldItemOffhand().isEmpty() )
+        {
+            renderPrintoutFirstPersonCentre(
+                event.getInterpolatedPitch(),
+                event.getEquipProgress(),
+                event.getSwingProgress(),
+                stack
+            );
+        }
+        else
+        {
+            renderPrintoutFirstPersonSide(
+                event.getHand() == EnumHand.MAIN_HAND ? player.getPrimaryHand() : player.getPrimaryHand().opposite(),
+                event.getEquipProgress(),
+                event.getSwingProgress(),
+                stack
+            );
+        }
+        GlStateManager.popMatrix();
+    }
+
+    /**
+     * Renders a pocket computer to one side of the player.
+     *
+     * @param side          The side to render on
+     * @param equipProgress The equip progress of this item
+     * @param swingProgress The swing progress of this item
+     * @param stack         The stack to render
+     * @see ItemRenderer#renderMapFirstPersonSide(float, EnumHandSide, float, ItemStack)
+     */
+    private void renderPrintoutFirstPersonSide( EnumHandSide side, float equipProgress, float swingProgress, ItemStack stack )
+    {
+        Minecraft minecraft = Minecraft.getMinecraft();
+        float offset = side == EnumHandSide.RIGHT ? 1f : -1f;
+        GlStateManager.translate( offset * 0.125f, -0.125f, 0f );
+
+        // If the player is not invisible then render a single arm
+        if( !minecraft.player.isInvisible() )
+        {
+            GlStateManager.pushMatrix();
+            GlStateManager.rotate( offset * 10f, 0f, 0f, 1f );
+            minecraft.getItemRenderer().renderArmFirstPerson( equipProgress, swingProgress, side );
+            GlStateManager.popMatrix();
+        }
+
+        // Setup the appropriate transformations. This is just copied from the
+        // corresponding method in ItemRenderer. 
+        GlStateManager.pushMatrix();
+        GlStateManager.translate( offset * 0.51f, -0.08f + equipProgress * -1.2f, -0.75f );
+        float f1 = MathHelper.sqrt( swingProgress );
+        float f2 = MathHelper.sin( f1 * (float) Math.PI );
+        float f3 = -0.5f * f2;
+        float f4 = 0.4f * MathHelper.sin( f1 * ((float) Math.PI * 2f) );
+        float f5 = -0.3f * MathHelper.sin( swingProgress * (float) Math.PI );
+        GlStateManager.translate( offset * f3, f4 - 0.3f * f2, f5 );
+        GlStateManager.rotate( f2 * -45f, 1f, 0f, 0f );
+        GlStateManager.rotate( offset * f2 * -30f, 0f, 1f, 0f );
+
+        renderPrintoutFirstPerson( stack );
+
+        GlStateManager.popMatrix();
+    }
+
+    /**
+     * Render an item in the middle of the screen
+     *
+     * @param pitch         The pitch of the player
+     * @param equipProgress The equip progress of this item
+     * @param swingProgress The swing progress of this item
+     * @param stack         The stack to render
+     * @see ItemRenderer#renderMapFirstPerson(float, float, float)
+     */
+    private void renderPrintoutFirstPersonCentre( float pitch, float equipProgress, float swingProgress, ItemStack stack )
+    {
+        ItemRenderer itemRenderer = Minecraft.getMinecraft().getItemRenderer();
+
+        // Setup the appropriate transformations. This is just copied from the
+        // corresponding method in ItemRenderer.
+        float swingRt = MathHelper.sqrt( swingProgress );
+        float tX = -0.2f * MathHelper.sin( swingProgress * (float) Math.PI );
+        float tZ = -0.4f * MathHelper.sin( swingRt * (float) Math.PI );
+        GlStateManager.translate( 0f, -tX / 2f, tZ );
+        float pitchAngle = itemRenderer.getMapAngleFromPitch( pitch );
+        GlStateManager.translate( 0f, 0.04f + equipProgress * -1.2f + pitchAngle * -0.5f, -0.72f );
+        GlStateManager.rotate( pitchAngle * -85f, 1f, 0f, 0f );
+        itemRenderer.renderArms();
+        float rX = MathHelper.sin( swingRt * (float) Math.PI );
+        GlStateManager.rotate( rX * 20f, 1f, 0f, 0f );
+        GlStateManager.scale( 2f, 2f, 2f );
+
+        renderPrintoutFirstPerson( stack );
+    }
+
+
+    private static void renderPrintoutFirstPerson( ItemStack stack )
+    {
+        // Setup various transformations. Note that these are partially adapated from the corresponding method
+        // in ItemRenderer.renderMapFirstPerson
+        GlStateManager.disableLighting();
+
+        GlStateManager.rotate( 180f, 0f, 1f, 0f );
+        GlStateManager.rotate( 180f, 0f, 0f, 1f );
+        GlStateManager.scale( 0.42f, 0.42f, -0.42f );
+        GlStateManager.translate( -0.5f, -0.48f, 0.0f );
+
+        drawPrintout( stack );
+
+        GlStateManager.enableLighting();
+    }
+
+    @SubscribeEvent
+    public void onRenderInFrame( RenderItemInFrameEvent event )
+    {
+        ItemStack stack = event.getItem();
+        if( stack.getItem() != ComputerCraft.Items.printout ) return;
+
+        event.setCanceled( true );
+
+        GlStateManager.disableLighting();
+
+        // Move a little bit forward to ensure we're not clipping with the frame
+        GlStateManager.translate( 0.0f, 0.0f, -0.001f );
+        GlStateManager.rotate( 180f, 0f, 0f, 1f );
+        GlStateManager.scale( 0.95f, 0.95f, -0.95f );
+        GlStateManager.translate( -0.5f, -0.5f, 0.0f );
+
+        drawPrintout( stack );
+
+        GlStateManager.enableLighting();
+    }
+
+    private static void drawPrintout( ItemStack stack )
+    {
+        int pages = ItemPrintout.getPageCount( stack );
+        boolean book = ItemPrintout.getType( stack ) == ItemPrintout.Type.Book;
+
+        double width = LINE_MAX_LENGTH * FONT_WIDTH + X_TEXT_MARGIN * 2;
+        double height = LINES_PER_PAGE * FONT_HEIGHT + Y_TEXT_MARGIN * 2;
+
+        // Non-books will be left aligned
+        if( !book ) width += offsetAt( pages );
+
+        double visualWidth = width, visualHeight = height;
+
+        // Meanwhile books will be centred
+        if( book )
+        {
+            visualWidth += 2 * COVER_SIZE + 2 * offsetAt( pages );
+            visualHeight += 2 * COVER_SIZE;
+        }
+
+        double max = Math.max( visualHeight, visualWidth );
+
+        // Scale the printout to fit correctly.
+        double scale = 1.0 / max;
+        GlStateManager.scale( scale, scale, scale );
+        GlStateManager.translate( (max - width) / 2.0f, (max - height) / 2.0f, 0.0f );
+
+        drawBorder( 0, 0, -0.01, 0, pages, book );
+        drawText( X_TEXT_MARGIN, Y_TEXT_MARGIN, 0, ItemPrintout.getText( stack ), ItemPrintout.getColours( stack ) );
+    }
+}

src/main/java/dan200/computercraft/client/render/ModelTransformer.java

@@ -189,7 +189,7 @@ public final class ModelTransformer
         private BakedQuadBuilder( VertexFormat format )
         {
             this.format = format;
-            this.vertexData = new int[ format.getNextOffset() ];
+            this.vertexData = new int[ format.getSize() ];
         }
 
         @Nonnull

src/main/java/dan200/computercraft/client/render/PrintoutRenderer.java

@@ -0,0 +1,169 @@
+package dan200.computercraft.client.render;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.client.gui.FixedWidthFontRenderer;
+import dan200.computercraft.core.terminal.TextBuffer;
+import dan200.computercraft.shared.util.Palette;
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.BufferBuilder;
+import net.minecraft.client.renderer.GlStateManager;
+import net.minecraft.client.renderer.Tessellator;
+import net.minecraft.client.renderer.vertex.DefaultVertexFormats;
+import net.minecraft.util.ResourceLocation;
+import org.lwjgl.opengl.GL11;
+
+import static dan200.computercraft.client.gui.FixedWidthFontRenderer.FONT_HEIGHT;
+import static dan200.computercraft.shared.media.items.ItemPrintout.LINES_PER_PAGE;
+
+public class PrintoutRenderer
+{
+    private static final ResourceLocation BG = new ResourceLocation( "computercraft", "textures/gui/printout.png" );
+    private static final double BG_SIZE = 256.0;
+
+    /**
+     * Width of a page
+     */
+    public static final int X_SIZE = 172;
+
+    /**
+     * Height of a page
+     */
+    public static final int Y_SIZE = 209;
+
+    /**
+     * Padding between the left and right of a page and the text
+     */
+    public static final int X_TEXT_MARGIN = 13;
+
+    /**
+     * Padding between the top and bottom of a page and the text
+     */
+    public static final int Y_TEXT_MARGIN = 11;
+
+    /**
+     * Width of the extra page texture
+     */
+    private static final int X_FOLD_SIZE = 12;
+
+    /**
+     * Size of the leather cover
+     */
+    public static final int COVER_SIZE = 12;
+
+    private static final int COVER_Y = Y_SIZE;
+    private static final int COVER_X = X_SIZE + 4 * X_FOLD_SIZE;
+
+    public static void drawText( int x, int y, int start, TextBuffer[] text, TextBuffer[] colours )
+    {
+        FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer) ComputerCraft.getFixedWidthFontRenderer();
+
+        for( int line = 0; line < LINES_PER_PAGE && line < text.length; ++line )
+        {
+            fontRenderer.drawString( text[ start + line ], x, y + line * FONT_HEIGHT, colours[ start + line ], null, 0, 0, false, Palette.DEFAULT );
+        }
+    }
+
+    public static void drawText( int x, int y, int start, String[] text, String[] colours )
+    {
+        GlStateManager.color( 1.0f, 1.0f, 1.0f, 1.0f );
+        GlStateManager.enableBlend();
+        GlStateManager.enableTexture2D();
+
+        FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer) ComputerCraft.getFixedWidthFontRenderer();
+
+        for( int line = 0; line < LINES_PER_PAGE && line < text.length; ++line )
+        {
+            fontRenderer.drawString( new TextBuffer( text[ start + line ] ), x, y + line * FONT_HEIGHT, new TextBuffer( colours[ start + line ] ), null, 0, 0, false, Palette.DEFAULT );
+        }
+    }
+
+    public static void drawBorder( double x, double y, double z, int page, int pages, boolean isBook )
+    {
+        GlStateManager.color( 1.0f, 1.0f, 1.0f, 1.0f );
+        GlStateManager.enableBlend();
+        GlStateManager.enableTexture2D();
+
+        Minecraft.getMinecraft().getTextureManager().bindTexture( BG );
+
+        Tessellator tessellator = Tessellator.getInstance();
+        BufferBuilder buffer = tessellator.getBuffer();
+        buffer.begin( GL11.GL_QUADS, DefaultVertexFormats.POSITION_TEX );
+
+        int leftPages = page;
+        int rightPages = pages - page - 1;
+
+        if( isBook )
+        {
+            // Border
+            double offset = offsetAt( pages );
+            final double left = x - 4 - offset;
+            final double right = x + X_SIZE + offset - 4;
+
+            // Left and right border
+            drawTexture( buffer, left - 4, y - 8, z - 0.02, COVER_X, 0, COVER_SIZE, Y_SIZE + COVER_SIZE * 2 );
+            drawTexture( buffer, right, y - 8, z - 0.02, COVER_X + COVER_SIZE, 0, COVER_SIZE, Y_SIZE + COVER_SIZE * 2 );
+
+            // Draw centre panel (just stretched texture, sorry).
+            drawTexture( buffer,
+                x - offset, y, z - 0.02, X_SIZE + offset * 2, Y_SIZE,
+                COVER_X + COVER_SIZE / 2, COVER_SIZE, COVER_SIZE, Y_SIZE
+            );
+
+            double borderX = left;
+            while( borderX < right )
+            {
+                double thisWidth = Math.min( right - borderX, X_SIZE );
+                drawTexture( buffer, borderX, y - 8, z - 0.02, 0, COVER_Y, thisWidth, COVER_SIZE );
+                drawTexture( buffer, borderX, y + Y_SIZE - 4, z - 0.02, 0, COVER_Y + COVER_SIZE, thisWidth, COVER_SIZE );
+                borderX += thisWidth;
+            }
+        }
+
+        // Left half
+        drawTexture( buffer, x, y, z, X_FOLD_SIZE * 2, 0, X_SIZE / 2, Y_SIZE );
+        for( int n = 0; n <= leftPages; n++ )
+        {
+            drawTexture( buffer,
+                x - offsetAt( n ), y, z - 1e-3 * n,
+                // Use the left "bold" fold for the outermost page
+                n == leftPages ? 0 : X_FOLD_SIZE, 0,
+                X_FOLD_SIZE, Y_SIZE
+            );
+        }
+
+        // Right half
+        drawTexture( buffer, x + X_SIZE / 2, y, z, X_FOLD_SIZE * 2 + X_SIZE / 2, 0, X_SIZE / 2, Y_SIZE );
+        for( int n = 0; n <= rightPages; n++ )
+        {
+            drawTexture( buffer,
+                x + (X_SIZE - X_FOLD_SIZE) + offsetAt( n ), y, z - 1e-3 * n,
+                // Two folds, then the main page. Use the right "bold" fold for the outermost page.
+                X_FOLD_SIZE * 2 + X_SIZE + (n == rightPages ? X_FOLD_SIZE : 0), 0,
+                X_FOLD_SIZE, Y_SIZE
+            );
+        }
+
+        tessellator.draw();
+    }
+
+    private static void drawTexture( BufferBuilder buffer, double x, double y, double z, double u, double v, double width, double height )
+    {
+        buffer.pos( x, y + height, z ).tex( u / BG_SIZE, (v + height) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y + height, z ).tex( (u + width) / BG_SIZE, (v + height) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y, z ).tex( (u + width) / BG_SIZE, v / BG_SIZE ).endVertex();
+        buffer.pos( x, y, z ).tex( u / BG_SIZE, v / BG_SIZE ).endVertex();
+    }
+
+    private static void drawTexture( BufferBuilder buffer, double x, double y, double z, double width, double height, double u, double v, double tWidth, double tHeight )
+    {
+        buffer.pos( x, y + height, z ).tex( u / BG_SIZE, (v + tHeight) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y + height, z ).tex( (u + tWidth) / BG_SIZE, (v + tHeight) / BG_SIZE ).endVertex();
+        buffer.pos( x + width, y, z ).tex( (u + tWidth) / BG_SIZE, v / BG_SIZE ).endVertex();
+        buffer.pos( x, y, z ).tex( u / BG_SIZE, v / BG_SIZE ).endVertex();
+    }
+
+    public static double offsetAt( int page )
+    {
+        return 32 * (1 - Math.pow( 1.2, -page ));
+    }
+}

src/main/java/dan200/computercraft/client/render/RenderOverlayCable.java

@@ -54,8 +54,6 @@ public class RenderOverlayCable
         GlStateManager.depthMask( false );
         GlStateManager.pushMatrix();
 
-        EnumFacing direction = type != PeripheralType.Cable ? cable.getDirection() : null;
-
         {
             EntityPlayer player = event.getPlayer();
             double x = player.lastTickPosX + (player.posX - player.lastTickPosX) * event.getPartialTicks();
@@ -78,7 +76,7 @@ public class RenderOverlayCable
 
             for( EnumFacing facing : EnumFacing.VALUES )
             {
-                if( direction == facing || BlockCable.isCable( world, pos.offset( facing ) ) )
+                if( BlockCable.doesConnectVisually( state, world, pos, facing ) )
                 {
                     flags |= 1 << facing.ordinal();
 

src/main/java/dan200/computercraft/client/render/TileEntityCableRenderer.java

@@ -71,7 +71,7 @@ public class TileEntityCableRenderer extends TileEntitySpecialRenderer<TileCable
         buffer.setTranslation( x - pos.getX(), y - pos.getY(), z - pos.getZ() );
         buffer.noColor();
 
-        ForgeHooksClient.setRenderLayer( block.getBlockLayer() );
+        ForgeHooksClient.setRenderLayer( block.getRenderLayer() );
 
         // See BlockRendererDispatcher#renderBlockDamage
         TextureAtlasSprite breakingTexture = mc.getTextureMapBlocks().getAtlasSprite( "minecraft:blocks/destroy_stage_" + destroyStage );

src/main/java/dan200/computercraft/client/render/TileEntityMonitorRenderer.java

@@ -10,7 +10,7 @@ import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.client.gui.FixedWidthFontRenderer;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.core.terminal.TextBuffer;
-import dan200.computercraft.shared.common.ClientTerminal;
+import dan200.computercraft.shared.peripheral.monitor.ClientMonitor;
 import dan200.computercraft.shared.peripheral.monitor.TileMonitor;
 import dan200.computercraft.shared.util.Colour;
 import dan200.computercraft.shared.util.DirectionUtil;
@@ -18,6 +18,7 @@ import dan200.computercraft.shared.util.Palette;
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.renderer.BufferBuilder;
 import net.minecraft.client.renderer.GlStateManager;
+import net.minecraft.client.renderer.OpenGlHelper;
 import net.minecraft.client.renderer.Tessellator;
 import net.minecraft.client.renderer.tileentity.TileEntitySpecialRenderer;
 import net.minecraft.client.renderer.vertex.DefaultVertexFormats;
@@ -43,25 +44,24 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
     private void renderMonitorAt( TileMonitor monitor, double posX, double posY, double posZ, float f, int i )
     {
         // Render from the origin monitor
-        TileMonitor origin = monitor.getOrigin();
-        if( origin == null )
-        {
-            return;
-        }
+        ClientMonitor originTerminal = monitor.getClientMonitor();
 
-        // Ensure each monitor is rendered only once
-        long renderFrame = ComputerCraft.getRenderFrame();
-        if( origin.m_lastRenderFrame == renderFrame )
-        {
-            return;
-        }
-        else
-        {
-            origin.m_lastRenderFrame = renderFrame;
-        }
-
-        boolean redraw = origin.pollChanged();
+        if( originTerminal == null ) return;
+        TileMonitor origin = originTerminal.getOrigin();
         BlockPos monitorPos = monitor.getPos();
+
+        // Ensure each monitor terminal is rendered only once. We allow rendering a specific tile
+        // multiple times in a single frame to ensure compatibility with shaders which may run a 
+        // pass multiple times.
+        long renderFrame = ComputerCraft.getRenderFrame();
+        if( originTerminal.lastRenderFrame == renderFrame && !monitorPos.equals( originTerminal.lastRenderPos ) )
+        {
+            return;
+        }
+
+        originTerminal.lastRenderFrame = renderFrame;
+        originTerminal.lastRenderPos = monitorPos;
+
         BlockPos originPos = origin.getPos();
         posX += originPos.getX() - monitorPos.getX();
         posY += originPos.getY() - monitorPos.getY();
@@ -94,34 +94,34 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
             BufferBuilder renderer = tessellator.getBuffer();
 
             // Get terminal
-            ClientTerminal clientTerminal = (ClientTerminal)origin.getTerminal();
-            Terminal terminal = (clientTerminal != null) ? clientTerminal.getTerminal() : null;
-            redraw = redraw || (clientTerminal != null && clientTerminal.hasTerminalChanged());
+            boolean redraw = originTerminal.pollTerminalChanged();
 
             // Draw the contents
             GlStateManager.depthMask( false );
+            OpenGlHelper.setLightmapTextureCoords( OpenGlHelper.lightmapTexUnit, 0xFF, 0xFF );
             GlStateManager.disableLighting();
             mc.entityRenderer.disableLightmap();
             try
             {
+                Terminal terminal = originTerminal.getTerminal();
                 if( terminal != null )
                 {
                     Palette palette = terminal.getPalette();
 
                     // Allocate display lists
-                    if( origin.m_renderDisplayList < 0 )
+                    if( originTerminal.renderDisplayLists == null )
                     {
-                        origin.m_renderDisplayList = GlStateManager.glGenLists( 3 );
+                        originTerminal.createLists();
                         redraw = true;
                     }
 
                     // Draw a terminal
-                    boolean greyscale = !clientTerminal.isColour();
+                    boolean greyscale = !originTerminal.isColour();
                     int width = terminal.getWidth();
                     int height = terminal.getHeight();
                     int cursorX = terminal.getCursorX();
                     int cursorY = terminal.getCursorY();
-                    FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer)ComputerCraft.getFixedWidthFontRenderer();
+                    FixedWidthFontRenderer fontRenderer = (FixedWidthFontRenderer) ComputerCraft.getFixedWidthFontRenderer();
 
                     GlStateManager.pushMatrix();
                     try
@@ -135,7 +135,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
                         if( redraw )
                         {
                             // Build background display list
-                            GlStateManager.glNewList( origin.m_renderDisplayList, GL11.GL_COMPILE );
+                            GlStateManager.glNewList( originTerminal.renderDisplayLists[0], GL11.GL_COMPILE );
                             try
                             {
                                 double marginXSize = TileMonitor.RENDER_MARGIN / xScale;
@@ -149,7 +149,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
                                     GlStateManager.scale( 1.0, marginSquash, 1.0 );
                                     GlStateManager.translate( 0.0, -marginYSize / marginSquash, 0.0 );
                                     fontRenderer.drawStringBackgroundPart( 0, 0, terminal.getBackgroundColourLine( 0 ), marginXSize, marginXSize, greyscale, palette );
-                                    GlStateManager.translate( 0.0, ( marginYSize + height * FixedWidthFontRenderer.FONT_HEIGHT ) / marginSquash, 0.0 );
+                                    GlStateManager.translate( 0.0, (marginYSize + height * FixedWidthFontRenderer.FONT_HEIGHT) / marginSquash, 0.0 );
                                     fontRenderer.drawStringBackgroundPart( 0, 0, terminal.getBackgroundColourLine( height - 1 ), marginXSize, marginXSize, greyscale, palette );
                                 }
                                 finally
@@ -174,7 +174,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
                                 GlStateManager.glEndList();
                             }
                         }
-                        GlStateManager.callList( origin.m_renderDisplayList );
+                        GlStateManager.callList( originTerminal.renderDisplayLists[0] );
                         GlStateManager.resetColor();
 
                         // Draw text
@@ -182,7 +182,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
                         if( redraw )
                         {
                             // Build text display list
-                            GlStateManager.glNewList( origin.m_renderDisplayList + 1, GL11.GL_COMPILE );
+                            GlStateManager.glNewList( originTerminal.renderDisplayLists[1], GL11.GL_COMPILE );
                             try
                             {
                                 // Lines
@@ -202,7 +202,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
                                 GlStateManager.glEndList();
                             }
                         }
-                        GlStateManager.callList( origin.m_renderDisplayList + 1 );
+                        GlStateManager.callList( originTerminal.renderDisplayLists[1] );
                         GlStateManager.resetColor();
 
                         // Draw cursor
@@ -210,7 +210,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
                         if( redraw )
                         {
                             // Build cursor display list
-                            GlStateManager.glNewList( origin.m_renderDisplayList + 2, GL11.GL_COMPILE );
+                            GlStateManager.glNewList( originTerminal.renderDisplayLists[2], GL11.GL_COMPILE );
                             try
                             {
                                 // Cursor
@@ -236,7 +236,7 @@ public class TileEntityMonitorRenderer extends TileEntitySpecialRenderer<TileMon
                         }
                         if( ComputerCraft.getGlobalCursorBlink() )
                         {
-                            GlStateManager.callList( origin.m_renderDisplayList + 2 );
+                            GlStateManager.callList( originTerminal.renderDisplayLists[2] );
                             GlStateManager.resetColor();
                         }
                     }

src/main/java/dan200/computercraft/client/render/TurtleSmartItemModel.java

@@ -167,7 +167,7 @@ public class TurtleSmartItemModel implements IBakedModel, IResourceManagerReload
         ModelResourceLocation baseModelLocation = TileEntityTurtleRenderer.getTurtleModel( combo.m_family, combo.m_colour );
         ModelResourceLocation overlayModelLocation = TileEntityTurtleRenderer.getTurtleOverlayModel( combo.m_family, combo.m_overlay, combo.m_christmas );
         IBakedModel baseModel = modelManager.getModel( baseModelLocation );
-        IBakedModel overlayModel = (overlayModelLocation != null) ? modelManager.getModel( baseModelLocation ) : null;
+        IBakedModel overlayModel = (overlayModelLocation != null) ? modelManager.getModel( overlayModelLocation ) : null;
         Matrix4f transform = combo.m_flip ? s_flip : s_identity;
         Pair<IBakedModel, Matrix4f> leftModel = (combo.m_leftUpgrade != null) ? combo.m_leftUpgrade.getModel( null, TurtleSide.Left ) : null;
         Pair<IBakedModel, Matrix4f> rightModel = (combo.m_rightUpgrade != null) ? combo.m_rightUpgrade.getModel( null, TurtleSide.Right ) : null;

src/main/java/dan200/computercraft/core/apis/BufferAPI.java

@@ -6,13 +6,12 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.terminal.TextBuffer;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.getString;
 import static dan200.computercraft.core.apis.ArgumentHelper.optInt;
@@ -41,27 +40,28 @@ public class BufferAPI implements ILuaAPI
             };
         }
 
+        @Nonnull
         @Override
-        public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+        public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
         {
             switch( method )
             {
                 case 0:
                 {
                     // len
-                    return new Object[] { m_buffer.length() };
+                    return MethodResult.of( m_buffer.length() );
                 }
                 case 1:
                 {
                     // tostring
-                    return new Object[] { m_buffer.toString() };
+                    return MethodResult.of( m_buffer.toString() );
                 }
                 case 2:
                 {
                     // read
                     int start = optInt( arguments, 0, 0 );
                     int end = optInt( arguments, 1, m_buffer.length() );
-                    return new Object[] { m_buffer.read( start, end ) };
+                    return MethodResult.of( m_buffer.read( start, end ) );
                 }
                 case 3:
                 {
@@ -70,7 +70,7 @@ public class BufferAPI implements ILuaAPI
                     int start = optInt( arguments, 1, 0 );
                     int end = optInt( arguments, 2, start + text.length() );
                     m_buffer.write( text, start, end );
-                    return null;
+                    return MethodResult.empty();
                 }
                 case 4:
                 {
@@ -79,14 +79,22 @@ public class BufferAPI implements ILuaAPI
                     int start = optInt( arguments, 1, 0 );
                     int end = optInt( arguments, 2, m_buffer.length() );
                     m_buffer.fill( text, start, end );
-                    return null;
+                    return MethodResult.empty();
                 }
                 default:
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             }
         }
+
+        @Nullable
+        @Override
+        @Deprecated
+        public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+        {
+            return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+        }
     }
 
     public BufferAPI( IAPIEnvironment _env )
@@ -110,8 +118,9 @@ public class BufferAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
@@ -124,12 +133,20 @@ public class BufferAPI implements ILuaAPI
                     throw ArgumentHelper.badArgument( 1, "positive number", Integer.toString( repetitions ) );
                 }
                 TextBuffer buffer = new TextBuffer( text, repetitions );
-                return new Object[] { new BufferLuaObject( buffer ) };
+                return MethodResult.of( new BufferLuaObject( buffer ) );
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/core/apis/ComputerAccess.java

@@ -3,14 +3,17 @@ package dan200.computercraft.core.apis;
 import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
 import dan200.computercraft.api.peripheral.IComputerAccess;
+import dan200.computercraft.core.computer.Computer;
+import dan200.computercraft.core.computer.IComputerOwned;
 import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.filesystem.FileSystemException;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashSet;
 import java.util.Set;
 
-public abstract class ComputerAccess implements IComputerAccess
+public abstract class ComputerAccess implements IComputerAccess, IComputerOwned
 {
     private final IAPIEnvironment m_environment;
     private final Set<String> m_mounts = new HashSet<>();
@@ -133,6 +136,13 @@ public abstract class ComputerAccess implements IComputerAccess
         m_environment.queueEvent( event, arguments );
     }
 
+    @Nullable
+    @Override
+    public Computer getComputer()
+    {
+        return m_environment.getComputer();
+    }
+
     private String findFreeLocation( String desiredLoc )
     {
         try

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -6,17 +6,18 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.apis.handles.BinaryInputHandle;
 import dan200.computercraft.core.apis.handles.BinaryOutputHandle;
 import dan200.computercraft.core.apis.handles.EncodedInputHandle;
 import dan200.computercraft.core.apis.handles.EncodedOutputHandle;
 import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.filesystem.FileSystemException;
+import dan200.computercraft.core.tracking.TrackingField;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.HashMap;
@@ -79,8 +80,9 @@ public class FSAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -88,13 +90,14 @@ public class FSAPI implements ILuaAPI
             {
                 // list
                 String path = getString( args, 0 );
+                m_env.addTrackingChange( TrackingField.FS_OPS );
                 try {
                     String[] results = m_fileSystem.list( path );
                     Map<Object,Object> table = new HashMap<>();
                     for(int i=0; i<results.length; ++i ) {
                         table.put( i+1, results[i] );
                     }
-                    return new Object[] { table };
+                    return MethodResult.of( table );
                 }
                 catch( FileSystemException e )
                 {
@@ -106,13 +109,13 @@ public class FSAPI implements ILuaAPI
                 // combine
                 String pathA = getString( args, 0 );
                 String pathB = getString( args, 1 );
-                return new Object[] { m_fileSystem.combine( pathA, pathB ) };
+                return MethodResult.of( m_fileSystem.combine( pathA, pathB ) );
             }
             case 2:
             {
                 // getName
                 String path = getString( args, 0 );
-                return new Object[]{ FileSystem.getName( path ) };
+                return MethodResult.of( FileSystem.getName( path ) );
             }
             case 3:
             {
@@ -120,7 +123,7 @@ public class FSAPI implements ILuaAPI
                 String path = getString( args, 0 );
                 try
                 {
-                    return new Object[]{ m_fileSystem.getSize( path ) };
+                    return MethodResult.of( m_fileSystem.getSize( path ) );
                 }
                 catch( FileSystemException e )
                 {
@@ -132,9 +135,9 @@ public class FSAPI implements ILuaAPI
                 // exists
                 String path = getString( args, 0 );
                 try {
-                    return new Object[]{ m_fileSystem.exists( path ) };
+                    return MethodResult.of( m_fileSystem.exists( path ) );
                 } catch( FileSystemException e ) {
-                    return new Object[]{ false };
+                    return MethodResult.of( false );
                 }
             }
             case 5:
@@ -142,9 +145,9 @@ public class FSAPI implements ILuaAPI
                 // isDir
                 String path = getString( args, 0 );
                 try {
-                    return new Object[]{ m_fileSystem.isDir( path ) };
+                    return MethodResult.of( m_fileSystem.isDir( path ) );
                 } catch( FileSystemException e ) {
-                    return new Object[]{ false };
+                    return MethodResult.of( false );
                 }
             }
             case 6:
@@ -152,9 +155,9 @@ public class FSAPI implements ILuaAPI
                 // isReadOnly
                 String path = getString( args, 0 );
                 try {
-                    return new Object[]{ m_fileSystem.isReadOnly( path ) };
+                    return MethodResult.of( m_fileSystem.isReadOnly( path ) );
                 } catch( FileSystemException e ) {
-                    return new Object[]{ false };
+                    return MethodResult.of( false );
                 }
             }
             case 7:
@@ -162,8 +165,9 @@ public class FSAPI implements ILuaAPI
                 // makeDir
                 String path = getString( args, 0 );
                 try {
+                    m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.makeDir( path );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -174,8 +178,9 @@ public class FSAPI implements ILuaAPI
                 String path = getString( args, 0 );
                 String dest = getString( args, 1 );
                 try {
+                    m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.move( path, dest );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -186,8 +191,9 @@ public class FSAPI implements ILuaAPI
                 String path = getString( args, 0 );
                 String dest = getString( args, 1 );
                 try {
+                    m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.copy( path, dest );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -197,8 +203,9 @@ public class FSAPI implements ILuaAPI
                 // delete
                 String path = getString( args, 0 );
                 try {
+                    m_env.addTrackingChange( TrackingField.FS_OPS );
                     m_fileSystem.delete( path );
-                    return null;
+                    return MethodResult.empty();
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -208,6 +215,7 @@ public class FSAPI implements ILuaAPI
                 // open
                 String path = getString( args, 0 );
                 String mode = getString( args, 1 );
+                m_env.addTrackingChange( TrackingField.FS_OPS );
                 try {
                     switch( mode )
                     {
@@ -215,43 +223,43 @@ public class FSAPI implements ILuaAPI
                         {
                             // Open the file for reading, then create a wrapper around the reader
                             InputStream reader = m_fileSystem.openForRead( path );
-                            return new Object[] { new EncodedInputHandle( reader ) };
+                            return MethodResult.of( new EncodedInputHandle( reader ) );
                         }
                         case "w":
                         {
                             // Open the file for writing, then create a wrapper around the writer
                             OutputStream writer = m_fileSystem.openForWrite( path, false );
-                            return new Object[] { new EncodedOutputHandle( writer ) };
+                            return MethodResult.of( new EncodedOutputHandle( writer ) );
                         }
                         case "a":
                         {
                             // Open the file for appending, then create a wrapper around the writer
                             OutputStream writer = m_fileSystem.openForWrite( path, true );
-                            return new Object[] { new EncodedOutputHandle( writer ) };
+                            return MethodResult.of( new EncodedOutputHandle( writer ) );
                         }
                         case "rb":
                         {
                             // Open the file for binary reading, then create a wrapper around the reader
                             InputStream reader = m_fileSystem.openForRead( path );
-                            return new Object[] { new BinaryInputHandle( reader ) };
+                            return MethodResult.of( new BinaryInputHandle( reader ) );
                         }
                         case "wb":
                         {
                             // Open the file for binary writing, then create a wrapper around the writer
                             OutputStream writer = m_fileSystem.openForWrite( path, false );
-                            return new Object[] { new BinaryOutputHandle( writer ) };
+                            return MethodResult.of( new BinaryOutputHandle( writer ) );
                         }
                         case "ab":
                         {
                             // Open the file for binary appending, then create a wrapper around the reader
                             OutputStream writer = m_fileSystem.openForWrite( path, true );
-                            return new Object[] { new BinaryOutputHandle( writer ) };
+                            return MethodResult.of( new BinaryOutputHandle( writer ) );
                         }
                         default:
                             throw new LuaException( "Unsupported mode" );
                     }
                 } catch( FileSystemException e ) {
-                    return new Object[] { null, e.getMessage() };
+                    return MethodResult.of( null, e.getMessage() );
                 }
             }
             case 12:
@@ -261,9 +269,9 @@ public class FSAPI implements ILuaAPI
                 try {
                     if( !m_fileSystem.exists( path ) )
                     {
-                        return null;
+                        return MethodResult.empty();
                     }
-                    return new Object[]{ m_fileSystem.getMountLabel( path ) };
+                    return MethodResult.of( m_fileSystem.getMountLabel( path ) );
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -276,9 +284,9 @@ public class FSAPI implements ILuaAPI
                     long freeSpace = m_fileSystem.getFreeSpace( path );
                     if( freeSpace >= 0 )
                     {
-                        return new Object[]{ freeSpace };
+                        return MethodResult.of( freeSpace );
                     }
-                    return new Object[]{ "unlimited" };
+                    return MethodResult.of( "unlimited" );
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -288,12 +296,13 @@ public class FSAPI implements ILuaAPI
                 // find
                 String path = getString( args, 0 );
                 try {
+                    m_env.addTrackingChange( TrackingField.FS_OPS );
                     String[] results = m_fileSystem.find( path );
                     Map<Object,Object> table = new HashMap<>();
                     for(int i=0; i<results.length; ++i ) {
                         table.put( i+1, results[i] );
                     }
-                    return new Object[] { table };
+                    return MethodResult.of( table );
                 } catch( FileSystemException e ) {
                     throw new LuaException( e.getMessage() );
                 }
@@ -302,13 +311,21 @@ public class FSAPI implements ILuaAPI
             {
                 // getDir
                 String path = getString( args, 0 );
-                return new Object[]{ FileSystem.getDirectory( path ) };
+                return MethodResult.of( FileSystem.getDirectory( path ) );
             }
             default:
             {
                 assert( false );
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/core/apis/HTTPAPI.java

@@ -6,13 +6,14 @@
 
 package dan200.computercraft.core.apis;
 
+import com.google.common.collect.ImmutableSet;
 import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.apis.http.*;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.Closeable;
 import java.io.IOException;
 import java.net.URI;
@@ -21,9 +22,14 @@ import java.util.*;
 import java.util.concurrent.Future;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.*;
+import static dan200.computercraft.core.apis.TableHelper.*;
 
 public class HTTPAPI implements ILuaAPI
 {
+    private static final Set<String> HTTP_METHODS = ImmutableSet.of(
+        "GET", "POST", "HEAD", "OPTIONS", "PUT", "DELETE"
+    );
+
     private final IAPIEnvironment m_apiEnvironment;
     private final List<Future<?>> m_httpTasks;
     private final Set<Closeable> m_closeables;
@@ -38,7 +44,7 @@ public class HTTPAPI implements ILuaAPI
     @Override
     public String[] getNames()
     {
-        return new String[] {
+        return new String[]{
             "http"
         };
     }
@@ -59,7 +65,7 @@ public class HTTPAPI implements ILuaAPI
     }
 
     @Override
-    public void shutdown( )
+    public void shutdown()
     {
         synchronized( m_httpTasks )
         {
@@ -89,64 +95,81 @@ public class HTTPAPI implements ILuaAPI
     @Override
     public String[] getMethodNames()
     {
-        return new String[] {
+        return new String[]{
             "request",
             "checkURL",
             "websocket",
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
-            case 0:
+            case 0: // request
             {
-                // request
-                // Get URL
-                String urlString = getString( args, 0 );
+                String urlString, postString, requestMethod;
+                Map<Object, Object> headerTable;
+                boolean binary, redirect;
 
-                // Get POST
-                String postString = optString( args, 1, null );
-
-                // Get Headers
-                Map<String, String> headers = null;
-                Map<Object, Object> table = optTable( args, 2, null );
-                if( table != null )
+                if( args.length >= 1 && args[0] instanceof Map )
                 {
-                    headers = new HashMap<>( table.size() );
-                    for( Object key : table.keySet() )
+                    Map<?, ?> options = (Map) args[0];
+                    urlString = getStringField( options, "url" );
+                    postString = optStringField( options, "body", null );
+                    headerTable = optTableField( options, "headers", null );
+                    binary = optBooleanField( options, "binary", false );
+                    requestMethod = optStringField( options, "method", null );
+                    redirect = optBooleanField( options, "redirect", true );
+
+                }
+                else
+                {
+                    // Get URL and post information
+                    urlString = getString( args, 0 );
+                    postString = optString( args, 1, null );
+                    headerTable = optTable( args, 2, null );
+                    binary = optBoolean( args, 3, false );
+                    requestMethod = null;
+                    redirect = true;
+                }
+
+                Map<String, String> headers = null;
+                if( headerTable != null )
+                {
+                    headers = new HashMap<>( headerTable.size() );
+                    for( Object key : headerTable.keySet() )
                     {
-                        Object value = table.get( key );
+                        Object value = headerTable.get( key );
                         if( key instanceof String && value instanceof String )
                         {
-                            headers.put( (String)key, (String)value );
+                            headers.put( (String) key, (String) value );
                         }
                     }
                 }
 
-                // Get binary
-                boolean binary = false;
-                if( args.length >= 4 )
+
+                if( requestMethod != null && !HTTP_METHODS.contains( requestMethod ) )
                 {
-                    binary = args[ 3 ] != null && !args[ 3 ].equals( Boolean.FALSE );
+                    throw new LuaException( "Unsupported HTTP method" );
                 }
 
                 // Make the request
                 try
                 {
                     URL url = HTTPRequest.checkURL( urlString );
-                    HTTPRequest request = new HTTPRequest( m_apiEnvironment, urlString, url, postString, headers, binary );
+                    HTTPRequest request = new HTTPRequest( m_apiEnvironment, urlString, url, postString, headers, binary, requestMethod, redirect );
                     synchronized( m_httpTasks )
                     {
                         m_httpTasks.add( HTTPExecutor.EXECUTOR.submit( request ) );
                     }
-                    return new Object[] { true };
+                    return MethodResult.of(true);
                 }
                 catch( HTTPRequestException e )
                 {
-                    return new Object[] { false, e.getMessage() };
+                    return MethodResult.of( false, e.getMessage() );
                 }
             }
             case 1:
@@ -164,11 +187,11 @@ public class HTTPAPI implements ILuaAPI
                     {
                         m_httpTasks.add( HTTPExecutor.EXECUTOR.submit( check ) );
                     }
-                    return new Object[] { true };
+                    return MethodResult.of( true );
                 }
                 catch( HTTPRequestException e )
                 {
-                    return new Object[] { false, e.getMessage() };
+                    return MethodResult.of( false, e.getMessage() );
                 }
             }
             case 2: // websocket
@@ -201,20 +224,28 @@ public class HTTPAPI implements ILuaAPI
                     {
                         m_httpTasks.add( connector );
                     }
-                    return new Object[] { true };
+                    return MethodResult.of(true);
                 }
                 catch( HTTPRequestException e )
                 {
-                    return new Object[] { false, e.getMessage() };
+                    return MethodResult.of( false, e.getMessage() );
                 }
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     public void addCloseable( Closeable closeable )
     {
         synchronized( m_closeables )

src/main/java/dan200/computercraft/core/apis/IAPIEnvironment.java

@@ -9,16 +9,19 @@ package dan200.computercraft.core.apis;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.computer.Computer;
 import dan200.computercraft.core.computer.IComputerEnvironment;
+import dan200.computercraft.core.computer.IComputerOwned;
 import dan200.computercraft.core.filesystem.FileSystem;
 import dan200.computercraft.core.terminal.Terminal;
+import dan200.computercraft.core.tracking.TrackingField;
 
-public interface IAPIEnvironment
+public interface IAPIEnvironment extends IComputerOwned
 {
     interface IPeripheralChangeListener
     {
         void onPeripheralChanged( int side, IPeripheral newPeripheral );
     }
-    
+
+    @Override
     Computer getComputer();
     int getComputerID();
     IComputerEnvironment getComputerEnvironment();
@@ -42,4 +45,11 @@ public interface IAPIEnvironment
 
     String getLabel();
     void setLabel( String label );
+
+    void addTrackingChange( TrackingField field, long change );
+
+    default void addTrackingChange( TrackingField field )
+    {
+        addTrackingChange( field, 1 );
+    }
 }

src/main/java/dan200/computercraft/core/apis/OSAPI.java

@@ -6,12 +6,12 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.shared.util.StringUtil;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.*;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.*;
@@ -221,7 +221,8 @@ public class OSAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    @Nonnull
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -229,7 +230,7 @@ public class OSAPI implements ILuaAPI
             {
                 // queueEvent
                 queueLuaEvent( getString( args, 0 ), trimArray( args, 1 ) );
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
@@ -238,7 +239,7 @@ public class OSAPI implements ILuaAPI
                 synchronized( m_timers )
                 {
                     m_timers.put( m_nextTimerToken, new Timer( (int)Math.round( timer / 0.05 ) ) );
-                    return new Object[] { m_nextTimerToken++ };
+                    return MethodResult.of( m_nextTimerToken++ );
                 }
             }
             case 2:
@@ -253,33 +254,33 @@ public class OSAPI implements ILuaAPI
                 {
                     int day = (time > m_time) ? m_day : (m_day + 1);
                     m_alarms.put( m_nextAlarmToken, new Alarm( time, day ) );
-                    return new Object[] { m_nextAlarmToken++ };
+                    return MethodResult.of( m_nextAlarmToken++ );
                 }
             }
             case 3:
             {
                 // shutdown
                 m_apiEnvironment.shutdown();
-                return null;
+                return MethodResult.empty();
             }
             case 4:
             {
                 // reboot
                 m_apiEnvironment.reboot();
-                return null;
+                return MethodResult.empty();
             }
             case 5:
             case 6:
             {
                 // computerID/getComputerID
-                return new Object[] { getComputerID() };
+                return MethodResult.of( getComputerID() );
             }
             case 7:
             {
                 // setComputerLabel
                 String label = optString( args, 0, null );
                 m_apiEnvironment.setLabel( StringUtil.normaliseLabel( label ) );
-                return null;
+                return MethodResult.empty();
             }
             case 8:
             case 9:
@@ -288,16 +289,16 @@ public class OSAPI implements ILuaAPI
                 String label = m_apiEnvironment.getLabel();
                 if( label != null )
                 {
-                    return new Object[] { label };
+                    return MethodResult.of( label );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 10:
             {
                 // clock
                 synchronized( m_timers )
                 {
-                    return new Object[] { m_clock * 0.05 };
+                    return MethodResult.of( m_clock * 0.05 );
                 }
             }
             case 11:
@@ -310,19 +311,19 @@ public class OSAPI implements ILuaAPI
                     {
                         // Get Hour of day (UTC)
                         Calendar c = Calendar.getInstance( TimeZone.getTimeZone( "UTC" ) );
-                        return new Object[] { getTimeForCalendar( c ) };
+                        return MethodResult.of( getTimeForCalendar( c ) );
                     }
                     case "local":
                     {
                         // Get Hour of day (local time)
                         Calendar c = Calendar.getInstance();
-                        return new Object[] { getTimeForCalendar( c ) };
+                        return MethodResult.of( getTimeForCalendar( c ) );
                     }
                     case "ingame":
                         // Get ingame hour
                         synchronized( m_alarms )
                         {
-                            return new Object[] { m_time };
+                            return MethodResult.of( m_time );
                         }
                     default:
                         throw new LuaException( "Unsupported operation" );
@@ -338,19 +339,19 @@ public class OSAPI implements ILuaAPI
                     {
                         // Get numbers of days since 1970-01-01 (utc)
                         Calendar c = Calendar.getInstance( TimeZone.getTimeZone( "UTC" ) );
-                        return new Object[] { getDayForCalendar( c ) };
+                        return MethodResult.of( getDayForCalendar( c ) );
                     }
                     case "local":
                     {
                         // Get numbers of days since 1970-01-01 (local time)
                         Calendar c = Calendar.getInstance();
-                        return new Object[] { getDayForCalendar( c ) };
+                        return MethodResult.of( getDayForCalendar( c ) );
                     }
                     case "ingame":
                         // Get game day
                         synchronized( m_alarms )
                         {
-                            return new Object[] { m_day };
+                            return MethodResult.of( m_day );
                         }
                     default:
                         throw new LuaException( "Unsupported operation" );
@@ -367,7 +368,7 @@ public class OSAPI implements ILuaAPI
                         m_timers.remove( token );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 14:
             {
@@ -380,7 +381,7 @@ public class OSAPI implements ILuaAPI
                         m_alarms.remove( token );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 15:
             {
@@ -392,21 +393,21 @@ public class OSAPI implements ILuaAPI
                     {
                         // Get utc epoch
                         Calendar c = Calendar.getInstance( TimeZone.getTimeZone( "UTC" ) );
-                        return new Object[] { getEpochForCalendar( c ) };
+                        return MethodResult.of( getEpochForCalendar( c ) );
                     }
                     case "local":
                     {
                         // Get local epoch
                         Calendar c = Calendar.getInstance();
-                        return new Object[] { getEpochForCalendar( c ) };
+                        return MethodResult.of( getEpochForCalendar( c ) );
                     }
                     case "ingame":
                         // Get in-game epoch
                         synchronized( m_alarms )
                         {
-                            return new Object[] {
+                            return MethodResult.of(
                                 m_day * 86400000 + (int) (m_time * 3600000.0f)
-                            };
+                            );
                         }
                     default:
                         throw new LuaException( "Unsupported operation" );
@@ -414,11 +415,18 @@ public class OSAPI implements ILuaAPI
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
     // Private methods
 
     private void queueLuaEvent( String event, Object[] args )

src/main/java/dan200/computercraft/core/apis/PeripheralAPI.java

@@ -8,17 +8,18 @@ package dan200.computercraft.core.apis;
 
 import dan200.computercraft.api.filesystem.IMount;
 import dan200.computercraft.api.filesystem.IWritableMount;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.computer.Computer;
 import dan200.computercraft.core.computer.ComputerThread;
 import dan200.computercraft.core.computer.ITask;
-import dan200.computercraft.core.filesystem.FileSystem;
+import dan200.computercraft.core.tracking.TrackingField;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -96,7 +97,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             m_attached = false;
         }
 
-        public Object[] call( ILuaContext context, String methodName, Object[] arguments ) throws LuaException, InterruptedException
+        public MethodResult call( ICallContext context, String methodName, Object[] arguments ) throws LuaException
         {
             int method = -1;
             synchronized( this )
@@ -108,6 +109,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             }
             if( method >= 0 )
             {
+                m_environment.addTrackingChange( TrackingField.PERIPHERAL_OPS );
                 return m_peripheral.callMethod( this, context, method, arguments );
             }
             else
@@ -180,10 +182,49 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             }
             return m_side;
         }
+
+        @Nonnull
+        @Override
+        public Map<String, IPeripheral> getAvailablePeripherals()
+        {
+            if( !m_attached )
+            {
+                throw new RuntimeException( "You are not attached to this Computer" );
+            }
+
+            Map<String, IPeripheral> peripherals = new HashMap<>();
+            for( PeripheralWrapper wrapper : m_peripherals )
+            {
+                if( wrapper != null && wrapper.isAttached() )
+                {
+                    peripherals.put( wrapper.getAttachmentName(), wrapper.getPeripheral() );
+                }
+            }
+
+            return Collections.unmodifiableMap( peripherals );
+        }
+
+        @Nullable
+        @Override
+        public IPeripheral getAvailablePeripheral( @Nonnull String name )
+        {
+            if( !m_attached )
+            {
+                throw new RuntimeException( "You are not attached to this Computer" );
+            }
+
+            for( PeripheralWrapper wrapper : m_peripherals )
+            {
+                if( wrapper != null && wrapper.isAttached() && wrapper.getAttachmentName().equals( name ) )
+                {
+                    return wrapper.getPeripheral();
+                }
+            }
+            return null;
+        }
     }
 
     private final IAPIEnvironment m_environment;
-    private FileSystem m_fileSystem;
     private final PeripheralWrapper[] m_peripherals;
     private boolean m_running;
 
@@ -285,7 +326,6 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
     {
         synchronized( m_peripherals )
         {
-            m_fileSystem = m_environment.getFileSystem();
             m_running = true;
             for( int i=0; i<6; ++i )
             {
@@ -312,7 +352,6 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                     wrapper.detach();
                 }
             }
-            m_fileSystem = null;
         }
     }
 
@@ -328,8 +367,9 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -349,7 +389,7 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                         }
                     }
                 }
-                return new Object[] { present };
+                return MethodResult.of( present );
             }
             case 1:
             {
@@ -368,10 +408,10 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                     }
                     if( type != null )
                     {
-                        return new Object[] { type };
+                        return MethodResult.of( type );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
@@ -395,9 +435,9 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
                     for(int i=0; i<methods.length; ++i ) {
                         table.put( i+1, methods[i] );
                     }
-                    return new Object[] { table };
+                    return MethodResult.of( table );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
@@ -422,11 +462,19 @@ public class PeripheralAPI implements ILuaAPI, IAPIEnvironment.IPeripheralChange
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+    
     // Privates
 
     private int parseSide( Object[] args ) throws LuaException

src/main/java/dan200/computercraft/core/apis/RedstoneAPI.java

@@ -6,12 +6,12 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.computer.Computer;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -56,8 +56,9 @@ public class RedstoneAPI implements ILuaAPI
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -69,7 +70,7 @@ public class RedstoneAPI implements ILuaAPI
                 {
                     table.put( i+1, Computer.s_sideNames[i] );
                 }
-                return new Object[] { table };
+                return MethodResult.of( table );
             }
             case 1:
             {
@@ -77,19 +78,19 @@ public class RedstoneAPI implements ILuaAPI
                 int side = parseSide( args );
                 boolean output = getBoolean( args, 1 );
                 m_environment.setOutput( side, output ? 15 : 0 );
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
                 // getOutput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getOutput( side ) > 0 };
+                return MethodResult.of( m_environment.getOutput( side ) > 0 );
             }
             case 3:
             {
                 // getInput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getInput( side ) > 0 };
+                return MethodResult.of( m_environment.getInput( side ) > 0 );
             }
             case 4:
             {
@@ -97,19 +98,19 @@ public class RedstoneAPI implements ILuaAPI
                 int side = parseSide( args );
                 int output = getInt( args, 1 );
                 m_environment.setBundledOutput( side, output );
-                return null;
+                return MethodResult.empty();
             }
             case 5:
             {
                 // getBundledOutput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getBundledOutput( side ) };
+                return MethodResult.of( m_environment.getBundledOutput( side ) );
             }
             case 6:
             {
                 // getBundledInput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getBundledInput( side ) };
+                return MethodResult.of( m_environment.getBundledInput( side ) );
             }
             case 7:
             {
@@ -117,7 +118,7 @@ public class RedstoneAPI implements ILuaAPI
                 int side = parseSide( args );
                 int mask = getInt( args, 1 );
                 int input = m_environment.getBundledInput( side );
-                return new Object[] { ((input & mask) == mask) };
+                return MethodResult.of( ((input & mask) == mask) );
             }
             case 8:
             case 9:
@@ -130,28 +131,36 @@ public class RedstoneAPI implements ILuaAPI
                     throw new LuaException( "Expected number in range 0-15" );
                 }
                 m_environment.setOutput( side, output );
-                return null;
+                return MethodResult.empty();
             }
             case 10:
             case 11:
             {
                 // getAnalogOutput/getAnalogueOutput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getOutput( side ) };
+                return MethodResult.of( m_environment.getOutput( side ) );
             }
             case 12:
             case 13:
             {
                 // getAnalogInput/getAnalogueInput
                 int side = parseSide( args );
-                return new Object[] { m_environment.getInput( side ) };
+                return MethodResult.of( m_environment.getInput( side ) );
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
     
     private int parseSide( Object[] args ) throws LuaException
     {

src/main/java/dan200/computercraft/core/apis/TableHelper.java

@@ -0,0 +1,214 @@
+package dan200.computercraft.core.apis;
+
+import dan200.computercraft.api.lua.LuaException;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.Map;
+
+/**
+ * Various helpers for tables
+ */
+public final class TableHelper
+{
+    private TableHelper()
+    {
+        throw new IllegalStateException( "Cannot instantiate singleton " + getClass().getName() );
+    }
+
+    @Nonnull
+    public static LuaException badKey( @Nonnull String key, @Nonnull String expected, @Nullable Object actual )
+    {
+        return badKey( key, expected, ArgumentHelper.getType( actual ) );
+    }
+
+    @Nonnull
+    public static LuaException badKey( @Nonnull String key, @Nonnull String expected, @Nonnull String actual )
+    {
+        return new LuaException( "bad field '" + key + "' (" + expected + " expected, got " + actual + ")" );
+    }
+
+    public static double getNumberField( @Nonnull Map<?, ?> table, @Nonnull String key ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value instanceof Number )
+        {
+            return ((Number) value).doubleValue();
+        }
+        else
+        {
+            throw badKey( key, "number", value );
+        }
+    }
+
+    public static int getIntField( @Nonnull Map<?, ?> table, @Nonnull String key ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value instanceof Number )
+        {
+            return (int) ((Number) value).longValue();
+        }
+        else
+        {
+            throw badKey( key, "number", value );
+        }
+    }
+
+    public static double getRealField( @Nonnull Map<?, ?> table, @Nonnull String key ) throws LuaException
+    {
+        return checkReal( key, getNumberField( table, key ) );
+    }
+
+    public static boolean getBooleanField( @Nonnull Map<?, ?> table, @Nonnull String key ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value instanceof Boolean )
+        {
+            return (Boolean) value;
+        }
+        else
+        {
+            throw badKey( key, "boolean", value );
+        }
+    }
+
+    @Nonnull
+    public static String getStringField( @Nonnull Map<?, ?> table, @Nonnull String key ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value instanceof String )
+        {
+            return (String) value;
+        }
+        else
+        {
+            throw badKey( key, "string", value );
+        }
+    }
+
+    @SuppressWarnings( "unchecked" )
+    @Nonnull
+    public static Map<Object, Object> getTableField( @Nonnull Map<?, ?> table, @Nonnull String key ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value instanceof Map )
+        {
+            return (Map<Object, Object>) value;
+        }
+        else
+        {
+            throw badKey( key, "table", value );
+        }
+    }
+
+    public static double optNumberField( @Nonnull Map<?, ?> table, @Nonnull String key, double def ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Number )
+        {
+            return ((Number) value).doubleValue();
+        }
+        else
+        {
+            throw badKey( key, "number", value );
+        }
+    }
+
+    public static int optIntField( @Nonnull Map<?, ?> table, @Nonnull String key, int def ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Number )
+        {
+            return (int) ((Number) value).longValue();
+        }
+        else
+        {
+            throw badKey( key, "number", value );
+        }
+    }
+
+    public static double optRealField( @Nonnull Map<?, ?> table, @Nonnull String key, double def ) throws LuaException
+    {
+        return checkReal( key, optNumberField( table, key, def ) );
+    }
+
+    public static boolean optBooleanField( @Nonnull Map<?, ?> table, @Nonnull String key, boolean def ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Boolean )
+        {
+            return (Boolean) value;
+        }
+        else
+        {
+            throw badKey( key, "boolean", value );
+        }
+    }
+
+    public static String optStringField( @Nonnull Map<?, ?> table, @Nonnull String key, String def ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof String )
+        {
+            return (String) value;
+        }
+        else
+        {
+            throw badKey( key, "string", value );
+        }
+    }
+
+    @SuppressWarnings( "unchecked" )
+    public static Map<Object, Object> optTableField( @Nonnull Map<?, ?> table, @Nonnull String key, Map<Object, Object> def ) throws LuaException
+    {
+        Object value = table.get( key );
+        if( value == null )
+        {
+            return def;
+        }
+        else if( value instanceof Map )
+        {
+            return (Map<Object, Object>) value;
+        }
+        else
+        {
+            throw badKey( key, "table", value );
+        }
+    }
+
+    private static double checkReal( @Nonnull String key, double value ) throws LuaException
+    {
+        if( Double.isNaN( value ) )
+        {
+            throw badKey( key, "number", "nan" );
+        }
+        else if( value == Double.POSITIVE_INFINITY )
+        {
+            throw badKey( key, "number", "inf" );
+        }
+        else if( value == Double.NEGATIVE_INFINITY )
+        {
+            throw badKey( key, "number", "-inf" );
+        }
+        else
+        {
+            return value;
+        }
+    }
+}

src/main/java/dan200/computercraft/core/apis/TermAPI.java

@@ -6,15 +6,15 @@
 
 package dan200.computercraft.core.apis;
 
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.core.computer.IComputerEnvironment;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.shared.util.Palette;
 import org.apache.commons.lang3.ArrayUtils;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 import static dan200.computercraft.core.apis.ArgumentHelper.*;
 
@@ -83,11 +83,9 @@ public class TermAPI implements ILuaAPI
         return colour;
     }
 
-    public static Object[] encodeColour( int colour ) throws LuaException
+    public static MethodResult encodeColour( int colour )
     {
-        return new Object[] {
-            1 << colour
-        };
+        return MethodResult.of( 1 << colour );
     }
 
     public static void setColour( Terminal terminal, int colour, double r, double g, double b )
@@ -99,8 +97,9 @@ public class TermAPI implements ILuaAPI
         }
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -119,7 +118,7 @@ public class TermAPI implements ILuaAPI
                     m_terminal.write( text );
                     m_terminal.setCursorPos( m_terminal.getCursorX() + text.length(), m_terminal.getCursorY() );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
@@ -129,7 +128,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.scroll(y);
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
@@ -140,7 +139,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setCursorPos( x, y );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
@@ -150,7 +149,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setCursorBlink( b );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 4:
             {
@@ -161,7 +160,7 @@ public class TermAPI implements ILuaAPI
                     x = m_terminal.getCursorX();
                     y = m_terminal.getCursorY();
                 }
-                return new Object[] { x + 1, y + 1 };
+                return MethodResult.of( x + 1, y + 1 );
             }
             case 5:
             {
@@ -172,7 +171,7 @@ public class TermAPI implements ILuaAPI
                     width = m_terminal.getWidth();
                     height = m_terminal.getHeight();
                 }                
-                return new Object[] { width, height };
+                return MethodResult.of( width, height );
             }
             case 6:
             {
@@ -181,7 +180,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.clear();
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 7:
             {
@@ -190,7 +189,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.clearLine();
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 8:
             case 9:
@@ -201,7 +200,7 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setTextColour( colour );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 10:
             case 11:
@@ -212,13 +211,13 @@ public class TermAPI implements ILuaAPI
                 {
                     m_terminal.setBackgroundColour( colour );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 12:
             case 13:
             {
                 // isColour/isColor
-                return new Object[] { m_environment.isColour() };
+                return MethodResult.of( m_environment.isColour() );
             }
             case 14:
             case 15:
@@ -248,7 +247,7 @@ public class TermAPI implements ILuaAPI
                     m_terminal.blit( text, textColour, backgroundColour );
                     m_terminal.setCursorPos( m_terminal.getCursorX() + text.length(), m_terminal.getCursorY() );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 19:
             case 20:
@@ -268,7 +267,7 @@ public class TermAPI implements ILuaAPI
                     double b = getReal( args, 3 );
                     setColour( m_terminal, colour, r, g, b );
                 }
-                return null;
+                return MethodResult.empty();
             }
             case 21:
             case 22:
@@ -279,18 +278,26 @@ public class TermAPI implements ILuaAPI
                 {
                     if ( m_terminal.getPalette() != null )
                     {
-                        return ArrayUtils.toObject( m_terminal.getPalette().getColour( colour ) );
+                        return MethodResult.of( (Object[]) ArrayUtils.toObject( m_terminal.getPalette().getColour( colour ) ) );
                     }
                 }
-                return null;
+                return MethodResult.empty();
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
-    
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     private static int getHighestBit( int group )
     {
         int bit = 0;

src/main/java/dan200/computercraft/core/apis/handles/BinaryInputHandle.java

@@ -1,10 +1,12 @@
 package dan200.computercraft.core.apis.handles;
 
 import com.google.common.io.ByteStreams;
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
@@ -13,6 +15,8 @@ import static dan200.computercraft.core.apis.ArgumentHelper.getInt;
 
 public class BinaryInputHandle extends HandleGeneric
 {
+    private static final int BUFFER_SIZE = 8192;
+
     private final InputStream m_stream;
 
     public BinaryInputHandle( InputStream reader )
@@ -32,8 +36,9 @@ public class BinaryInputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -45,26 +50,56 @@ public class BinaryInputHandle extends HandleGeneric
                     if( args.length > 0 && args[ 0 ] != null )
                     {
                         int count = getInt( args, 0 );
-                        if( count <= 0 || count >= 1024 * 16 )
+                        if( count < 0 )
                         {
-                            throw new LuaException( "Count out of range" );
+                            // Whilst this may seem absurd to allow reading 0 bytes, PUC Lua it so 
+                            // it seems best to remain somewhat consistent.
+                            throw new LuaException( "Cannot read a negative number of bytes" );
                         }
+                        else if( count <= BUFFER_SIZE )
+                        {
+                            // If we've got a small count, then allocate that and read it.
+                            byte[] bytes = new byte[ count ];
+                            int read = m_stream.read( bytes );
 
-                        byte[] bytes = new byte[ count ];
-                        count = m_stream.read( bytes );
-                        if( count < 0 ) return null;
-                        if( count < bytes.length ) bytes = Arrays.copyOf( bytes, count );
-                        return new Object[] { bytes };
+                            if( read < 0 ) return MethodResult.empty();
+                            if( read < count ) bytes = Arrays.copyOf( bytes, read );
+                            return MethodResult.of( bytes );
+                        }
+                        else
+                        {
+                            byte[] buffer = new byte[ BUFFER_SIZE ];
+
+                            // Read the initial set of bytes, failing if none are read.
+                            int read = m_stream.read( buffer, 0, Math.min( buffer.length, count ) );
+                            if( read == -1 ) return null;
+
+                            ByteArrayOutputStream out = new ByteArrayOutputStream( read );
+                            count -= read;
+                            out.write( buffer, 0, read );
+
+                            // Otherwise read until we either reach the limit or we no longer consume
+                            // the full buffer.
+                            while( read >= buffer.length && count > 0 )
+                            {
+                                read = m_stream.read( buffer, 0, Math.min( BUFFER_SIZE, count ) );
+                                if( read == -1 ) break;
+                                count -= read;
+                                out.write( buffer, 0, read );
+                            }
+
+                            return MethodResult.of( new Object[]{ out.toByteArray() } );
+                        }
                     }
                     else
                     {
                         int b = m_stream.read();
-                        return b == -1 ? null : new Object[] { b };
+                        return b == -1 ? MethodResult.empty() : MethodResult.of( b );
                     }
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 1:
                 // readAll
@@ -72,18 +107,18 @@ public class BinaryInputHandle extends HandleGeneric
                 try
                 {
                     byte[] out = ByteStreams.toByteArray( m_stream );
-                    return out == null ? null : new Object[] { out };
+                    return out == null ? MethodResult.empty() : MethodResult.of( out );
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 2:
                 //close
                 close();
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/BinaryOutputHandle.java

@@ -1,7 +1,8 @@
 package dan200.computercraft.core.apis.handles;
 
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.core.apis.ArgumentHelper;
 import dan200.computercraft.shared.util.StringUtil;
 
@@ -30,8 +31,9 @@ public class BinaryOutputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -54,7 +56,7 @@ public class BinaryOutputHandle extends HandleGeneric
                     {
                         throw ArgumentHelper.badArgument( 0, "string or number", args.length > 0 ? args[ 0 ] : null );
                     }
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
@@ -66,18 +68,18 @@ public class BinaryOutputHandle extends HandleGeneric
                 try
                 {
                     m_writer.flush();
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 2:
                 //close
                 close();
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/EncodedInputHandle.java

@@ -1,15 +1,18 @@
 package dan200.computercraft.core.apis.handles;
 
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
 import java.io.*;
 
-import static dan200.computercraft.core.apis.ArgumentHelper.*;
+import static dan200.computercraft.core.apis.ArgumentHelper.optInt;
 
 public class EncodedInputHandle extends HandleGeneric
 {
+    private static final int BUFFER_SIZE = 8192;
+
     private final BufferedReader m_reader;
 
     public EncodedInputHandle( BufferedReader reader )
@@ -55,8 +58,9 @@ public class EncodedInputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -68,16 +72,16 @@ public class EncodedInputHandle extends HandleGeneric
                     String line = m_reader.readLine();
                     if( line != null )
                     {
-                        return new Object[] { line };
+                        return MethodResult.of( line );
                     }
                     else
                     {
-                        return null;
+                        return MethodResult.empty();
                     }
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 1:
                 // readAll
@@ -95,38 +99,68 @@ public class EncodedInputHandle extends HandleGeneric
                             result.append( "\n" );
                         }
                     }
-                    return new Object[] { result.toString() };
+                    return MethodResult.of( result.toString() );
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 2:
                 // close
                 close();
-                return null;
+                return MethodResult.empty();
             case 3:
                 // read
                 checkOpen();
                 try
                 {
                     int count = optInt( args, 0, 1 );
-                    if( count <= 0 || count >= 1024 * 16 )
+                    if( count < 0 )
                     {
-                        throw new LuaException( "Count out of range" );
+                        // Whilst this may seem absurd to allow reading 0 characters, PUC Lua it so 
+                        // it seems best to remain somewhat consistent.
+                        throw new LuaException( "Cannot read a negative number of characters" );
+                    }
+                    else if( count <= BUFFER_SIZE )
+                    {
+                        // If we've got a small count, then allocate that and read it.
+                        char[] chars = new char[ count ];
+                        int read = m_reader.read( chars );
+
+                        return read < 0 ? MethodResult.empty() : MethodResult.of( new String( chars, 0, read ) );
+                    }
+                    else
+                    {
+                        // If we've got a large count, read in bunches of 8192.
+                        char[] buffer = new char[ BUFFER_SIZE ];
+
+                        // Read the initial set of characters, failing if none are read.
+                        int read = m_reader.read( buffer, 0, Math.min( buffer.length, count ) );
+                        if( read == -1 ) return null;
+
+                        StringBuilder out = new StringBuilder( read );
+                        count -= read;
+                        out.append( buffer, 0, read );
+
+                        // Otherwise read until we either reach the limit or we no longer consume
+                        // the full buffer.
+                        while( read >= BUFFER_SIZE && count > 0 )
+                        {
+                            read = m_reader.read( buffer, 0, Math.min( BUFFER_SIZE, count ) );
+                            if( read == -1 ) break;
+                            count -= read;
+                            out.append( buffer, 0, read );
+                        }
+
+                        return MethodResult.of( out.toString() );
                     }
-                    char[] bytes = new char[ count ];
-                    count = m_reader.read( bytes );
-                    if( count < 0 ) return null;
-                    String str = new String( bytes, 0, count );
-                    return new Object[] { str };
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/EncodedOutputHandle.java

@@ -1,7 +1,8 @@
 package dan200.computercraft.core.apis.handles;
 
-import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 
 import javax.annotation.Nonnull;
 import java.io.*;
@@ -53,8 +54,9 @@ public class EncodedOutputHandle extends HandleGeneric
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
     {
         switch( method )
         {
@@ -74,7 +76,7 @@ public class EncodedOutputHandle extends HandleGeneric
                 try
                 {
                     m_writer.write( text, 0, text.length() );
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
@@ -98,7 +100,7 @@ public class EncodedOutputHandle extends HandleGeneric
                 {
                     m_writer.write( text, 0, text.length() );
                     m_writer.newLine();
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
@@ -111,18 +113,18 @@ public class EncodedOutputHandle extends HandleGeneric
                 try
                 {
                     m_writer.flush();
-                    return null;
+                    return MethodResult.empty();
                 }
                 catch( IOException e )
                 {
-                    return null;
+                    return MethodResult.empty();
                 }
             case 3:
                 // close
                 close();
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 }

src/main/java/dan200/computercraft/core/apis/handles/HandleGeneric.java

@@ -1,8 +1,12 @@
 package dan200.computercraft.core.apis.handles;
 
+import dan200.computercraft.api.lua.ICallContext;
+import dan200.computercraft.api.lua.ILuaContext;
 import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.api.lua.LuaException;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.Closeable;
 import java.io.IOException;
 
@@ -32,4 +36,12 @@ public abstract class HandleGeneric implements ILuaObject
         {
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/core/apis/http/HTTPRequest.java

@@ -9,14 +9,14 @@ package dan200.computercraft.core.apis.http;
 import com.google.common.base.Joiner;
 import com.google.common.io.ByteStreams;
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.core.apis.IAPIEnvironment;
 import dan200.computercraft.core.apis.handles.BinaryInputHandle;
 import dan200.computercraft.core.apis.handles.EncodedInputHandle;
+import dan200.computercraft.core.tracking.TrackingField;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.io.*;
 import java.net.*;
 import java.util.Arrays;
@@ -78,8 +78,10 @@ public class HTTPRequest implements Runnable
     private final String m_postText;
     private final Map<String, String> m_headers;
     private boolean m_binary;
+    private final String m_method;
+    private final boolean m_followRedirects;
 
-    public HTTPRequest( IAPIEnvironment environment, String urlString, URL url, final String postText, final Map<String, String> headers, boolean binary ) throws HTTPRequestException
+    public HTTPRequest( IAPIEnvironment environment, String urlString, URL url, final String postText, final Map<String, String> headers, boolean binary, final String method, final boolean followRedirects ) throws HTTPRequestException
     {
         m_environment = environment;
         m_urlString = urlString;
@@ -87,6 +89,8 @@ public class HTTPRequest implements Runnable
         m_binary = binary;
         m_postText = postText;
         m_headers = headers;
+        m_method = method;
+        m_followRedirects = followRedirects;
     }
 
     @Override
@@ -101,7 +105,7 @@ public class HTTPRequest implements Runnable
         {
             // Queue the failure event if not.
             String error = e.getMessage();
-            m_environment.queueEvent( "http_failure", new Object[] { m_urlString, error == null ? "Could not connect" : error, null } );
+            m_environment.queueEvent( "http_failure", new Object[]{ m_urlString, error == null ? "Could not connect" : error, null } );
             return;
         }
 
@@ -119,6 +123,8 @@ public class HTTPRequest implements Runnable
             {
                 connection.setRequestMethod( "GET" );
             }
+            if( m_method != null ) connection.setRequestMethod( m_method );
+            connection.setInstanceFollowRedirects( m_followRedirects );
 
             // Set headers
             connection.setRequestProperty( "accept-charset", "UTF-8" );
@@ -134,6 +140,11 @@ public class HTTPRequest implements Runnable
                 }
             }
 
+            // Add request size and count to the tracker before opening the connection
+            m_environment.addTrackingChange( TrackingField.HTTP_REQUESTS );
+            m_environment.addTrackingChange( TrackingField.HTTP_UPLOAD,
+                getHeaderSize( connection.getRequestProperties() ) + (m_postText == null ? 0 : m_postText.length()) );
+
             // Send POST text
             if( m_postText != null )
             {
@@ -178,6 +189,9 @@ public class HTTPRequest implements Runnable
                 headers.put( header.getKey(), joiner.join( header.getValue() ) );
             }
 
+            m_environment.addTrackingChange( TrackingField.HTTP_DOWNLOAD,
+                getHeaderSize( connection.getHeaderFields() ) + result.length );
+
             InputStream contents = new ByteArrayInputStream( result );
             ILuaObject stream = wrapStream(
                 m_binary ? new BinaryInputHandle( contents ) : new EncodedInputHandle( contents, connection.getContentEncoding() ),
@@ -189,17 +203,17 @@ public class HTTPRequest implements Runnable
             // Queue the appropriate event.
             if( responseSuccess )
             {
-                m_environment.queueEvent( "http_success", new Object[] { m_urlString, stream } );
+                m_environment.queueEvent( "http_success", new Object[]{ m_urlString, stream } );
             }
             else
             {
-                m_environment.queueEvent( "http_failure", new Object[] { m_urlString, "Could not connect", stream } );
+                m_environment.queueEvent( "http_failure", new Object[]{ m_urlString, "Could not connect", stream } );
             }
         }
         catch( IOException e )
         {
             // There was an error
-            m_environment.queueEvent( "http_failure", new Object[] { m_urlString, "Could not connect", null } );
+            m_environment.queueEvent( "http_failure", new Object[]{ m_urlString, "Could not connect", null } );
         }
     }
 
@@ -209,8 +223,8 @@ public class HTTPRequest implements Runnable
         final int methodOffset = oldMethods.length;
 
         final String[] newMethods = Arrays.copyOf( oldMethods, oldMethods.length + 2 );
-        newMethods[ methodOffset + 0 ] = "getResponseCode";
-        newMethods[ methodOffset + 1 ] = "getResponseHeaders";
+        newMethods[methodOffset + 0] = "getResponseCode";
+        newMethods[methodOffset + 1] = "getResponseHeaders";
 
         return new ILuaObject()
         {
@@ -221,8 +235,9 @@ public class HTTPRequest implements Runnable
                 return newMethods;
             }
 
+            @Nonnull
             @Override
-            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] args ) throws LuaException, InterruptedException
+            public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] args ) throws LuaException
             {
                 if( method < methodOffset )
                 {
@@ -233,19 +248,38 @@ public class HTTPRequest implements Runnable
                     case 0:
                     {
                         // getResponseCode
-                        return new Object[] { responseCode };
+                        return MethodResult.of( responseCode );
                     }
                     case 1:
                     {
                         // getResponseHeaders
-                        return new Object[] { responseHeaders };
+                        return MethodResult.of( responseHeaders );
                     }
                     default:
                     {
-                        return null;
+                        return MethodResult.empty();
                     }
                 }
             }
+
+            @Nullable
+            @Override
+            @Deprecated
+            public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+            {
+                return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+            }
         };
     }
+
+    private static long getHeaderSize( Map<String, List<String>> headers )
+    {
+        long size = 0;
+        for( Map.Entry<String, List<String>> header : headers.entrySet() )
+        {
+            size += header.getKey() == null ? 0 : header.getKey().length();
+            for( String value : header.getValue() ) size += value == null ? 0 : value.length() + 1;
+        }
+        return size;
+    }
 }

src/main/java/dan200/computercraft/core/apis/http/WebsocketConnection.java

@@ -7,11 +7,10 @@
 package dan200.computercraft.core.apis.http;
 
 import com.google.common.base.Objects;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.core.apis.HTTPAPI;
 import dan200.computercraft.core.apis.IAPIEnvironment;
+import dan200.computercraft.core.tracking.TrackingField;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelHandlerContext;
@@ -71,7 +70,7 @@ public class WebsocketConnection extends SimpleChannelInboundHandler<Object> imp
     private void onClosed()
     {
         close( true );
-        computer.queueEvent( CLOSE_EVENT, new Object[] { url } );
+        computer.queueEvent( CLOSE_EVENT, new Object[]{ url } );
     }
 
     @Override
@@ -102,7 +101,7 @@ public class WebsocketConnection extends SimpleChannelInboundHandler<Object> imp
         if( !handshaker.isHandshakeComplete() )
         {
             handshaker.finishHandshake( ch, (FullHttpResponse) msg );
-            computer.queueEvent( SUCCESS_EVENT, new Object[] { url, this } );
+            computer.queueEvent( SUCCESS_EVENT, new Object[]{ url, this } );
             return;
         }
 
@@ -115,14 +114,19 @@ public class WebsocketConnection extends SimpleChannelInboundHandler<Object> imp
         WebSocketFrame frame = (WebSocketFrame) msg;
         if( frame instanceof TextWebSocketFrame )
         {
-            computer.queueEvent( MESSAGE_EVENT, new Object[] { url, ((TextWebSocketFrame) frame).text() } );
+            String data = ((TextWebSocketFrame) frame).text();
+
+            computer.addTrackingChange( TrackingField.WEBSOCKET_INCOMING, data.length() );
+            computer.queueEvent( MESSAGE_EVENT, new Object[]{ url, data } );
         }
         else if( frame instanceof BinaryWebSocketFrame )
         {
             ByteBuf data = frame.content();
-            byte[] converted = new byte[ data.readableBytes() ];
+            byte[] converted = new byte[data.readableBytes()];
             data.readBytes( converted );
-            computer.queueEvent( MESSAGE_EVENT, new Object[] { url, data } );
+
+            computer.addTrackingChange( TrackingField.WEBSOCKET_INCOMING, converted.length );
+            computer.queueEvent( MESSAGE_EVENT, new Object[]{ url, converted } );
         }
         else if( frame instanceof CloseWebSocketFrame )
         {
@@ -135,7 +139,7 @@ public class WebsocketConnection extends SimpleChannelInboundHandler<Object> imp
     public void exceptionCaught( ChannelHandlerContext ctx, Throwable cause )
     {
         ctx.close();
-        computer.queueEvent( FAILURE_EVENT, new Object[] {
+        computer.queueEvent( FAILURE_EVENT, new Object[]{
             url,
             cause instanceof WebSocketHandshakeException ? cause.getMessage() : "Could not connect"
         } );
@@ -145,37 +149,53 @@ public class WebsocketConnection extends SimpleChannelInboundHandler<Object> imp
     @Override
     public String[] getMethodNames()
     {
-        return new String[] { "receive", "send", "close" };
+        return new String[]{ "receive", "send", "close" };
     }
 
     @Nullable
     @Override
+    @Deprecated
     public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
+    @Nonnull
+    @Override
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
             case 0:
-                while( true )
+                checkOpen();
+                return MethodResult.pullEvent( MESSAGE_EVENT, new ILuaFunction()
                 {
-                    checkOpen();
-                    Object[] event = context.pullEvent( MESSAGE_EVENT );
-                    if( event.length >= 3 && Objects.equal( event[ 1 ], url ) )
+                    @Nonnull
+                    @Override
+                    public MethodResult call( @Nullable Object[] event ) throws LuaException
                     {
-                        return new Object[] { event[ 2 ] };
+                        if( event != null && event.length >= 3 && Objects.equal( event[1], url ) )
+                        {
+                            return MethodResult.of( event[2] );
+                        }
+
+                        checkOpen();
+                        return MethodResult.pullEvent( MESSAGE_EVENT, this );
                     }
-                }
+                } );
             case 1:
             {
                 checkOpen();
-                String text = arguments.length > 0 && arguments[ 0 ] != null ? arguments[ 0 ].toString() : "";
+                String text = arguments.length > 0 && arguments[0] != null ? arguments[0].toString() : "";
+                computer.addTrackingChange( TrackingField.WEBSOCKET_OUTGOING, text.length() );
                 channel.writeAndFlush( new TextWebSocketFrame( text ) );
-                return null;
+                return MethodResult.empty();
             }
             case 2:
                 close( true );
-                return null;
+                return MethodResult.empty();
             default:
-                return null;
+                return MethodResult.empty();
         }
     }
 

src/main/java/dan200/computercraft/core/apis/http/WebsocketConnector.java

@@ -21,6 +21,7 @@ import io.netty.handler.codec.http.HttpObjectAggregator;
 import io.netty.handler.codec.http.websocketx.WebSocketClientHandshaker;
 import io.netty.handler.codec.http.websocketx.WebSocketClientHandshakerFactory;
 import io.netty.handler.codec.http.websocketx.WebSocketVersion;
+import io.netty.handler.codec.http.websocketx.extensions.compression.WebSocketClientCompressionHandler;
 import io.netty.handler.ssl.SslContext;
 import io.netty.handler.ssl.SslContextBuilder;
 
@@ -34,7 +35,7 @@ import java.security.KeyStore;
 import java.util.Map;
 import java.util.concurrent.Future;
 
-/*
+/**
  * Provides functionality to verify and connect to a remote websocket.
  */
 public final class WebsocketConnector
@@ -177,7 +178,7 @@ public final class WebsocketConnector
                 httpHeaders.add( header.getKey(), header.getValue() );
             }
 
-            WebSocketClientHandshaker handshaker = WebSocketClientHandshakerFactory.newHandshaker( uri, WebSocketVersion.V13, null, false, httpHeaders );
+            WebSocketClientHandshaker handshaker = WebSocketClientHandshakerFactory.newHandshaker( uri, WebSocketVersion.V13, null, true, httpHeaders );
             final WebsocketConnection connection = new WebsocketConnection( environment, api, handshaker, address );
 
             new Bootstrap()
@@ -190,7 +191,12 @@ public final class WebsocketConnector
                     {
                         ChannelPipeline p = ch.pipeline();
                         if( ssl != null ) p.addLast( ssl.newHandler( ch.alloc(), uri.getHost(), port ) );
-                        p.addLast( new HttpClientCodec(), new HttpObjectAggregator( 8192 ), connection );
+                        p.addLast(
+                            new HttpClientCodec(),
+                            new HttpObjectAggregator( 8192 ),
+                            WebSocketClientCompressionHandler.INSTANCE,
+                            connection
+                        );
                     }
                 } )
                 .remoteAddress( socketAddress )

src/main/java/dan200/computercraft/core/computer/Computer.java

@@ -20,6 +20,8 @@ import dan200.computercraft.core.filesystem.FileSystemException;
 import dan200.computercraft.core.lua.CobaltLuaMachine;
 import dan200.computercraft.core.lua.ILuaMachine;
 import dan200.computercraft.core.terminal.Terminal;
+import dan200.computercraft.core.tracking.Tracking;
+import dan200.computercraft.core.tracking.TrackingField;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -167,6 +169,12 @@ public class Computer
             m_computer.setLabel( label );
         }
 
+        @Override
+        public void addTrackingChange( TrackingField field, long change )
+        {
+            Tracking.addValue( m_computer, field, change );
+        }
+
         public void onPeripheralChanged( int side, IPeripheral peripheral )
         {
             synchronized( m_computer.m_peripherals )
@@ -257,10 +265,18 @@ public class Computer
 
         @Nullable
         @Override
+        @Deprecated
         public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
         {
             return delegate.callMethod( context, method, arguments );
         }
+
+        @Nonnull
+        @Override
+        public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
+        {
+            return delegate.callMethod( context, method, arguments );
+        }
     }
 
     private static IMount s_romMount = null;
@@ -952,7 +968,7 @@ public class Computer
                 return;
             }
         }
-            
+
         final Computer computer = this;
         ITask task = new ITask() {
             @Override

src/main/java/dan200/computercraft/core/computer/ComputerThread.java

@@ -7,6 +7,7 @@
 package dan200.computercraft.core.computer;
 
 import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.core.tracking.Tracking;
 
 import java.util.HashSet;
 import java.util.Set;
@@ -68,17 +69,17 @@ public class ComputerThread
             s_stopped = false;
             if( s_threads == null || s_threads.length != ComputerCraft.computer_threads )
             {
-                s_threads = new Thread[ ComputerCraft.computer_threads ];
+                s_threads = new Thread[ComputerCraft.computer_threads];
             }
 
             SecurityManager manager = System.getSecurityManager();
             final ThreadGroup group = manager == null ? Thread.currentThread().getThreadGroup() : manager.getThreadGroup();
             for( int i = 0; i < s_threads.length; i++ )
             {
-                Thread thread = s_threads[ i ];
+                Thread thread = s_threads[i];
                 if( thread == null || !thread.isAlive() )
                 {
-                    thread = s_threads[ i ] = new Thread( group, new TaskExecutor(), "ComputerCraft-Computer-Manager-" + s_ManagerCounter.getAndIncrement() );
+                    thread = s_threads[i] = new Thread( group, new TaskExecutor(), "ComputerCraft-Computer-Manager-" + s_ManagerCounter.getAndIncrement() );
                     thread.setDaemon( true );
                     thread.start();
                 }
@@ -195,6 +196,8 @@ public class ComputerThread
                 thread.start();
             }
 
+            long start = System.nanoTime();
+
             // Execute the task
             runner.submit( task );
 
@@ -221,6 +224,23 @@ public class ComputerThread
                     // Interrupt the thread
                     if( !done )
                     {
+                        StringBuilder builder = new StringBuilder( "Terminating " );
+                        if( computer != null )
+                        {
+                            builder.append( "computer " ).append( computer.getID() );
+                        }
+                        else
+                        {
+                            builder.append( "unknown computer" );
+                        }
+
+                        builder.append( ". Thread is currently running" );
+                        for( StackTraceElement element : thread.getStackTrace() )
+                        {
+                            builder.append( "\n  at " ).append( element );
+                        }
+                        ComputerCraft.log.error( builder.toString() );
+
                         thread.interrupt();
                         thread = null;
                         runner = null;
@@ -229,6 +249,10 @@ public class ComputerThread
             }
             finally
             {
+                long stop = System.nanoTime();
+                Computer computer = task.getOwner();
+                if( computer != null ) Tracking.addTaskTiming( computer, stop - start );
+
                 // Re-add it back onto the queue or remove it
                 synchronized( s_taskLock )
                 {

src/main/java/dan200/computercraft/core/computer/IComputerOwned.java

@@ -0,0 +1,9 @@
+package dan200.computercraft.core.computer;
+
+import javax.annotation.Nullable;
+
+public interface IComputerOwned
+{
+    @Nullable
+    Computer getComputer();
+}

src/main/java/dan200/computercraft/core/computer/MainThread.java

@@ -6,14 +6,17 @@
 
 package dan200.computercraft.core.computer;
 
-import java.util.LinkedList;
+import dan200.computercraft.core.tracking.Tracking;
+
+import java.util.ArrayDeque;
+import java.util.Queue;
 
 public class MainThread
 {
     private static final int MAX_TASKS_PER_TICK = 1000;
     private static final int MAX_TASKS_TOTAL = 50000;
 
-    private static final LinkedList<ITask> m_outstandingTasks = new LinkedList<>();
+    private static final Queue<ITask> m_outstandingTasks = new ArrayDeque<>();
     private static final Object m_nextUnusedTaskIDLock = new Object();
     private static long m_nextUnusedTaskID = 0;
 
@@ -31,7 +34,7 @@ public class MainThread
         {
             if( m_outstandingTasks.size() < MAX_TASKS_TOTAL )
             {
-                m_outstandingTasks.addLast( task );
+                m_outstandingTasks.offer( task );
                 return true;
             }
         }
@@ -46,14 +49,17 @@ public class MainThread
             ITask task = null;
             synchronized( m_outstandingTasks )
             {
-                if( m_outstandingTasks.size() > 0 )
-                {
-                    task = m_outstandingTasks.removeFirst();
-                }
+                task = m_outstandingTasks.poll();
             }
             if( task != null )
             {
+                long start = System.nanoTime();
                 task.execute();
+
+                long stop = System.nanoTime();
+                Computer computer = task.getOwner();
+                if( computer != null ) Tracking.addServerTiming( computer, stop - start );
+
                 ++tasksThisTick;
             }
             else

src/main/java/dan200/computercraft/core/lua/CobaltCallContext.java

@@ -0,0 +1,87 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.ICallContext;
+import dan200.computercraft.api.lua.ILuaTask;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.core.computer.Computer;
+import dan200.computercraft.core.computer.ITask;
+import dan200.computercraft.core.computer.MainThread;
+
+import javax.annotation.Nonnull;
+
+class CobaltCallContext implements ICallContext
+{
+    private final Computer computer;
+
+    CobaltCallContext( Computer computer )
+    {
+        this.computer = computer;
+    }
+
+    @Override
+    public long issueMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException
+    {
+        // Issue command
+        final long taskID = MainThread.getUniqueTaskID();
+        final ITask iTask = new ITask()
+        {
+            @Override
+            public Computer getOwner()
+            {
+                return computer;
+            }
+
+            @Override
+            public void execute()
+            {
+                try
+                {
+                    Object[] results = task.execute();
+                    if( results != null )
+                    {
+                        Object[] eventArguments = new Object[results.length + 2];
+                        eventArguments[0] = taskID;
+                        eventArguments[1] = true;
+                        System.arraycopy( results, 0, eventArguments, 2, results.length );
+                        computer.queueEvent( "task_complete", eventArguments );
+                    }
+                    else
+                    {
+                        computer.queueEvent( "task_complete", new Object[]{ taskID, true } );
+                    }
+                }
+                catch( LuaException e )
+                {
+                    computer.queueEvent( "task_complete", new Object[]{
+                        taskID, false, e.getMessage()
+                    } );
+                }
+                catch( Throwable t )
+                {
+                    if( ComputerCraft.logPeripheralErrors )
+                    {
+                        ComputerCraft.log.error( "Error running task", t );
+                    }
+                    computer.queueEvent( "task_complete", new Object[]{
+                        taskID, false, "Java Exception Thrown: " + t.toString()
+                    } );
+                }
+            }
+        };
+        if( MainThread.queueTask( iTask ) )
+        {
+            return taskID;
+        }
+        else
+        {
+            throw new LuaException( "Task limit exceeded" );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/lua/CobaltLuaContext.java

@@ -0,0 +1,191 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.ILuaContextTask;
+import dan200.computercraft.api.lua.ILuaTask;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.core.computer.Computer;
+import org.squiddev.cobalt.LuaError;
+import org.squiddev.cobalt.LuaState;
+import org.squiddev.cobalt.LuaThread;
+import org.squiddev.cobalt.UnwindThrowable;
+
+import javax.annotation.Nonnull;
+import java.lang.ref.WeakReference;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.SynchronousQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * An ugly wrapper for {@link ILuaContext} style calls, which executes them on a separate thread.
+ */
+class CobaltLuaContext extends CobaltCallContext implements ILuaContext
+{
+    private static final ThreadGroup group = new ThreadGroup( "ComputerCraft-Lua" );
+    private static final AtomicInteger threadCounter = new AtomicInteger();
+    private static final ExecutorService threads = new ThreadPoolExecutor(
+        4, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS, new SynchronousQueue<>(),
+        task -> {
+            Thread thread = new Thread( group, task, group.getName() + "-" + threadCounter.incrementAndGet() );
+            if( !thread.isDaemon() ) thread.setDaemon( true );
+            if( thread.getPriority() != Thread.NORM_PRIORITY ) thread.setPriority( Thread.NORM_PRIORITY );
+            return thread;
+        }
+    );
+
+    private boolean done = false;
+    private Object[] values;
+    private LuaError exception;
+    private final Semaphore yield = new Semaphore();
+    private final Semaphore resume = new Semaphore();
+    private WeakReference<LuaThread> thread;
+
+    CobaltLuaContext( Computer computer, LuaState state )
+    {
+        super( computer );
+        this.thread = state.getCurrentThread().getReference();
+    }
+
+    @Nonnull
+    @Override
+    @Deprecated
+    public Object[] pullEvent( String filter ) throws LuaException, InterruptedException
+    {
+        Object[] results = pullEventRaw( filter );
+        if( results.length >= 1 && results[0].equals( "terminate" ) )
+        {
+            throw new LuaException( "Terminated", 0 );
+        }
+        return results;
+    }
+
+    @Nonnull
+    @Override
+    @Deprecated
+    public Object[] pullEventRaw( String filter ) throws InterruptedException
+    {
+        return yield( new Object[]{ filter } );
+    }
+
+    @Nonnull
+    @Override
+    @Deprecated
+    public Object[] yield( Object[] yieldArgs ) throws InterruptedException
+    {
+        if( done ) throw new IllegalStateException( "Cannot yield when complete" );
+
+        values = yieldArgs;
+        yield.signal();
+
+        // Every 30 seconds check to see if the coroutine has been GCed
+        // if so then abort this task.
+        while( !resume.await( 30000 ) )
+        {
+            if( thread.get() == null ) throw new InterruptedException( "Orphaned async task" );
+        }
+
+        return values;
+    }
+
+    @Override
+    @Deprecated
+    public Object[] executeMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException, InterruptedException
+    {
+        // Issue task
+        final long taskID = issueMainThreadTask( task );
+
+        // Wait for response
+        while( true )
+        {
+            Object[] response = pullEvent( "task_complete" );
+            if( response.length >= 3 && response[1] instanceof Number && response[2] instanceof Boolean )
+            {
+                if( ((Number) response[1]).intValue() == taskID )
+                {
+                    Object[] returnValues = new Object[response.length - 3];
+                    if( (Boolean) response[2] )
+                    {
+                        // Extract the return values from the event and return them
+                        System.arraycopy( response, 3, returnValues, 0, returnValues.length );
+                        return returnValues;
+                    }
+                    else
+                    {
+                        // Extract the error message from the event and raise it
+                        if( response.length >= 4 && response[3] instanceof String )
+                        {
+                            throw new LuaException( (String) response[3] );
+                        }
+                        else
+                        {
+                            throw new LuaException();
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    void execute( ILuaContextTask task )
+    {
+        threads.submit( () -> {
+            try
+            {
+                values = task.execute( this );
+            }
+            catch( LuaException e )
+            {
+                exception = new LuaError( e.getMessage(), e.getLevel() );
+            }
+            catch( InterruptedException e )
+            {
+                exception = new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+            }
+            finally
+            {
+                done = true;
+                yield.signal();
+            }
+        } );
+    }
+
+    void resume( Object[] args )
+    {
+        values = args;
+        resume.signal();
+    }
+
+    Object[] await( LuaState state, CobaltLuaMachine machine ) throws LuaError, UnwindThrowable
+    {
+        if( !done )
+        {
+            try
+            {
+                yield.await();
+            }
+            catch( InterruptedException e )
+            {
+                throw new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+            }
+        }
+
+        if( done )
+        {
+            if( exception != null ) throw exception;
+            return values;
+        }
+        else
+        {
+            LuaThread.yield( state, machine.toValues( values ) );
+            throw new IllegalStateException( "Unreachable" );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/lua/CobaltLuaMachine.java

@@ -7,14 +7,9 @@
 package dan200.computercraft.core.lua;
 
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.ILuaObject;
-import dan200.computercraft.api.lua.ILuaTask;
-import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.lua.ILuaAPI;
+import dan200.computercraft.api.lua.ILuaObject;
 import dan200.computercraft.core.computer.Computer;
-import dan200.computercraft.core.computer.ITask;
-import dan200.computercraft.core.computer.MainThread;
 import org.squiddev.cobalt.*;
 import org.squiddev.cobalt.compiler.CompileException;
 import org.squiddev.cobalt.compiler.LoadState;
@@ -27,7 +22,6 @@ import org.squiddev.cobalt.function.VarArgFunction;
 import org.squiddev.cobalt.lib.*;
 import org.squiddev.cobalt.lib.platform.AbstractResourceManipulator;
 
-import javax.annotation.Nonnull;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -76,7 +70,7 @@ public class CobaltLuaMachine implements ILuaMachine
                 int count = ++this.count;
                 if( count > 100000 )
                 {
-                    if( m_hardAbortMessage != null ) LuaThread.yield( state, NONE );
+                    if( m_hardAbortMessage != null ) throw new LuaError( m_hardAbortMessage );
                     this.count = 0;
                 }
                 else
@@ -90,7 +84,7 @@ public class CobaltLuaMachine implements ILuaMachine
             @Override
             public void poll() throws LuaError
             {
-                if( m_hardAbortMessage != null ) LuaThread.yield( state, NONE );
+                if( m_hardAbortMessage != null ) throw new LuaError( m_hardAbortMessage );
                 handleSoftAbort();
             }
 
@@ -125,7 +119,7 @@ public class CobaltLuaMachine implements ILuaMachine
         if( ComputerCraft.debug_enable ) m_globals.load( state, new DebugLib() );
 
         // Register custom load/loadstring provider which automatically adds prefixes.
-        LibFunction.bind( state, m_globals, PrefixLoader.class, new String[]{ "load", "loadstring" } );
+        LibFunction.bind( m_globals, PrefixLoader.class, new String[]{ "load", "loadstring" } );
 
         // Remove globals we don't want to expose
         m_globals.rawset( "collectgarbage", Constants.NIL );
@@ -216,18 +210,13 @@ public class CobaltLuaMachine implements ILuaMachine
                 resumeArgs = varargsOf( valueOf( eventName ), toValues( arguments ) );
             }
 
-            Varargs results = m_mainRoutine.resume( resumeArgs );
+            LuaValue filter = LuaThread.run( m_mainRoutine, resumeArgs ).first();
             if( m_hardAbortMessage != null )
             {
                 throw new LuaError( m_hardAbortMessage );
             }
-            else if( !results.first().checkBoolean() )
-            {
-                throw new LuaError( results.arg( 2 ).checkString() );
-            }
             else
             {
-                LuaValue filter = results.arg( 2 );
                 if( filter.isString() )
                 {
                     m_eventFilter = filter.toString();
@@ -246,6 +235,7 @@ public class CobaltLuaMachine implements ILuaMachine
         }
         catch( LuaError e )
         {
+            if( ComputerCraft.logPeripheralErrors ) ComputerCraft.log.error( "Main thread crashed", e );
             m_mainRoutine.abandon();
             m_mainRoutine = null;
         }
@@ -302,181 +292,12 @@ public class CobaltLuaMachine implements ILuaMachine
     {
         LuaTable table = new LuaTable();
         String[] methods = object.getMethodNames();
-        for( int i = 0; i < methods.length; ++i )
+        for( int method = 0; method < methods.length; method++ )
         {
-            if( methods[ i ] != null )
+            if( methods[method] != null )
             {
-                final int method = i;
-                final ILuaObject apiObject = object;
-                final String methodName = methods[ i ];
-                table.rawset( methodName, new VarArgFunction()
-                {
-                    @Override
-                    public Varargs invoke( final LuaState state, Varargs _args ) throws LuaError
-                    {
-                        Object[] arguments = toObjects( _args, 1 );
-                        Object[] results;
-                        try
-                        {
-                            results = apiObject.callMethod( new ILuaContext()
-                            {
-                                @Nonnull
-                                @Override
-                                public Object[] pullEvent( String filter ) throws LuaException, InterruptedException
-                                {
-                                    Object[] results = pullEventRaw( filter );
-                                    if( results.length >= 1 && results[ 0 ].equals( "terminate" ) )
-                                    {
-                                        throw new LuaException( "Terminated", 0 );
-                                    }
-                                    return results;
-                                }
-
-                                @Nonnull
-                                @Override
-                                public Object[] pullEventRaw( String filter ) throws InterruptedException
-                                {
-                                    return yield( new Object[] { filter } );
-                                }
-
-                                @Nonnull
-                                @Override
-                                public Object[] yield( Object[] yieldArgs ) throws InterruptedException
-                                {
-                                    try
-                                    {
-                                        Varargs results = LuaThread.yield( state, toValues( yieldArgs ) );
-                                        return toObjects( results, 1 );
-                                    }
-                                    catch( OrphanedThread e )
-                                    {
-                                        throw new InterruptedException();
-                                    }
-                                    catch( Throwable e )
-                                    {
-                                        throw new RuntimeException( e );
-                                    }
-                                }
-
-                                @Override
-                                public long issueMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException
-                                {
-                                    // Issue command
-                                    final long taskID = MainThread.getUniqueTaskID();
-                                    final ITask iTask = new ITask()
-                                    {
-                                        @Override
-                                        public Computer getOwner()
-                                        {
-                                            return m_computer;
-                                        }
-
-                                        @Override
-                                        public void execute()
-                                        {
-                                            try
-                                            {
-                                                Object[] results = task.execute();
-                                                if( results != null )
-                                                {
-                                                    Object[] eventArguments = new Object[ results.length + 2 ];
-                                                    eventArguments[ 0 ] = taskID;
-                                                    eventArguments[ 1 ] = true;
-                                                    System.arraycopy( results, 0, eventArguments, 2, results.length );
-                                                    m_computer.queueEvent( "task_complete", eventArguments );
-                                                }
-                                                else
-                                                {
-                                                    m_computer.queueEvent( "task_complete", new Object[] { taskID, true } );
-                                                }
-                                            }
-                                            catch( LuaException e )
-                                            {
-                                                m_computer.queueEvent( "task_complete", new Object[] {
-                                                    taskID, false, e.getMessage()
-                                                } );
-                                            }
-                                            catch( Throwable t )
-                                            {
-                                                if( ComputerCraft.logPeripheralErrors )
-                                                {
-                                                    ComputerCraft.log.error( "Error running task", t );
-                                                }
-                                                m_computer.queueEvent( "task_complete", new Object[] {
-                                                    taskID, false, "Java Exception Thrown: " + t.toString()
-                                                } );
-                                            }
-                                        }
-                                    };
-                                    if( MainThread.queueTask( iTask ) )
-                                    {
-                                        return taskID;
-                                    }
-                                    else
-                                    {
-                                        throw new LuaException( "Task limit exceeded" );
-                                    }
-                                }
-
-                                @Override
-                                public Object[] executeMainThreadTask( @Nonnull final ILuaTask task ) throws LuaException, InterruptedException
-                                {
-                                    // Issue task
-                                    final long taskID = issueMainThreadTask( task );
-
-                                    // Wait for response
-                                    while( true )
-                                    {
-                                        Object[] response = pullEvent( "task_complete" );
-                                        if( response.length >= 3 && response[ 1 ] instanceof Number && response[ 2 ] instanceof Boolean )
-                                        {
-                                            if( ((Number) response[ 1 ]).intValue() == taskID )
-                                            {
-                                                Object[] returnValues = new Object[ response.length - 3 ];
-                                                if( (Boolean) response[ 2 ] )
-                                                {
-                                                    // Extract the return values from the event and return them
-                                                    System.arraycopy( response, 3, returnValues, 0, returnValues.length );
-                                                    return returnValues;
-                                                }
-                                                else
-                                                {
-                                                    // Extract the error message from the event and raise it
-                                                    if( response.length >= 4 && response[ 3 ] instanceof String )
-                                                    {
-                                                        throw new LuaException( (String) response[ 3 ] );
-                                                    }
-                                                    else
-                                                    {
-                                                        throw new LuaException();
-                                                    }
-                                                }
-                                            }
-                                        }
-                                    }
-
-                                }
-                            }, method, arguments );
-                        }
-                        catch( InterruptedException e )
-                        {
-                            throw new OrphanedThread();
-                        }
-                        catch( LuaException e )
-                        {
-                            throw new LuaError( e.getMessage(), e.getLevel() );
-                        }
-                        catch( Throwable t )
-                        {
-                            if( ComputerCraft.logPeripheralErrors )
-                            {
-                                ComputerCraft.log.error( "Error calling " + methodName + " on " + apiObject, t );
-                            }
-                            throw new LuaError( "Java Exception Thrown: " + t.toString(), 0 );
-                        }
-                        return toValues( results );
-                    }
-                } );
+                final String methodName = methods[method];
+                table.rawset( methodName, new CobaltWrapperFunction( this, m_computer, object, method, methodName ) );
             }
         }
         return table;
@@ -544,7 +365,7 @@ public class CobaltLuaMachine implements ILuaMachine
         }
     }
 
-    private Varargs toValues( Object[] objects )
+    Varargs toValues( Object[] objects )
     {
         if( objects == null || objects.length == 0 )
         {
@@ -635,7 +456,7 @@ public class CobaltLuaMachine implements ILuaMachine
         }
     }
 
-    private static Object[] toObjects( Varargs values, int startIdx )
+    static Object[] toObjects( Varargs values, int startIdx )
     {
         int count = values.count();
         Object[] objects = new Object[ count - startIdx + 1 ];
@@ -703,13 +524,23 @@ public class CobaltLuaMachine implements ILuaMachine
             if( remaining <= 0 )
             {
                 LuaValue s;
+                state.getCurrentThread().disableYield();
                 try
                 {
                     s = OperationHelper.call( state, func );
-                } catch (LuaError e)
+                }
+                catch( UnwindThrowable e )
+                {
+                    throw new IOException( "Impossible yield within load" );
+                }
+                catch( LuaError e )
                 {
                     throw new IOException( e );
                 }
+                finally
+                {
+                    state.getCurrentThread().enableYield();
+                }
 
                 if( s.isNil() )
                 {
@@ -735,4 +566,5 @@ public class CobaltLuaMachine implements ILuaMachine
             return bytes[offset++];
         }
     }
+
 }

src/main/java/dan200/computercraft/core/lua/CobaltWrapperFunction.java

@@ -0,0 +1,292 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.ILuaFunction;
+import dan200.computercraft.api.lua.ILuaObject;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
+import dan200.computercraft.core.computer.Computer;
+import org.squiddev.cobalt.*;
+import org.squiddev.cobalt.debug.DebugState;
+import org.squiddev.cobalt.function.VarArgFunction;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+class CobaltWrapperFunction extends VarArgFunction implements Resumable<CobaltWrapperFunction.State>
+{
+    private final CobaltLuaMachine machine;
+    private final Computer computer;
+    private final CobaltCallContext callContext;
+
+    private final ILuaObject delegate;
+    private final int method;
+    private final String methodName;
+
+    CobaltWrapperFunction( CobaltLuaMachine machine, Computer computer, ILuaObject delegate, int method, String methodName )
+    {
+        this.machine = machine;
+        this.computer = computer;
+        this.callContext = new CobaltCallContext( computer );
+        this.delegate = delegate;
+        this.method = method;
+        this.methodName = methodName;
+    }
+
+    @Override
+    public Varargs invoke( final LuaState state, Varargs args ) throws LuaError, UnwindThrowable
+    {
+        MethodResult future;
+        try
+        {
+            future = delegate.callMethod( callContext, method, CobaltLuaMachine.toObjects( args, 1 ) );
+        }
+        catch( LuaException e )
+        {
+            throw new LuaError( e.getMessage(), e.getLevel() );
+        }
+        catch( Exception e )
+        {
+            if( ComputerCraft.logPeripheralErrors )
+            {
+                ComputerCraft.log.error( "Error calling " + methodName + " on " + delegate, e );
+            }
+            throw new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+        }
+
+        // Verify we've a "well formed" future
+        if( future == null )
+        {
+            ComputerCraft.log.error( "Null result from " + delegate );
+            throw new LuaError( "Java Exception Thrown: Null result" );
+        }
+
+        // Fast path for immediate results
+        if( future instanceof MethodResult.Immediate )
+        {
+            return machine.toValues( ((MethodResult.Immediate) future).getResult() );
+        }
+
+        State context = new State();
+        try
+        {
+            return runFuture( state, context, future );
+        }
+        catch( UnwindThrowable e )
+        {
+            // Push our state onto the stack if need-be. Normally this wouldn't be safe and we 
+            // should do this at the very beginning, but we know that we won't be calling anything 
+            // else which will push to the resume stack.
+            DebugState ds = state.debug.getDebugState();
+            state.debug.onCall( ds, this, context );
+            throw e;
+        }
+    }
+
+    @Override
+    public Varargs resume( LuaState state, State context, Varargs args ) throws LuaError, UnwindThrowable
+    {
+        Varargs result;
+        try
+        {
+            result = doResume( state, context, args );
+        }
+        catch( LuaError e )
+        {
+            state.debug.onReturn();
+            throw e;
+        }
+        catch( Exception e )
+        {
+            state.debug.onReturn();
+            throw new LuaError( e );
+        }
+
+        state.debug.onReturn();
+        return result;
+    }
+
+    private Varargs doResume( LuaState state, State context, Varargs args ) throws LuaError, UnwindThrowable
+    {
+        MethodResult future = context.pending;
+        if( future instanceof MethodResult.OnEvent )
+        {
+            MethodResult.OnEvent onEvent = (MethodResult.OnEvent) future;
+            if( !onEvent.isRaw() && args.first().toString().equals( "terminate" ) )
+            {
+                throw new LuaError( "Terminated", 0 );
+            }
+
+            return runCallback( state, context, CobaltLuaMachine.toObjects( args, 1 ) );
+        }
+        else if( future instanceof MethodResult.OnMainThread )
+        {
+            if( args.arg( 2 ).isNumber() && args.arg( 3 ).isBoolean() && args.arg( 2 ).toLong() == context.taskId )
+            {
+                if( args.arg( 3 ).toBoolean() )
+                {
+                    // Extract the return values from the event and return them
+                    return runFuture( state, context, context.taskResult );
+                }
+                else
+                {
+                    // Extract the error message from the event and raise it
+                    throw new LuaError( args.arg( 4 ) );
+                }
+            }
+            else
+            {
+                LuaThread.yield( state, ValueFactory.valueOf( "task_complete" ) );
+                throw new IllegalStateException( "Unreachable" );
+            }
+        }
+        else if( future instanceof MethodResult.WithLuaContext )
+        {
+            context.luaContext.resume( CobaltLuaMachine.toObjects( args, 1 ) );
+            return runCallback( state, context, context.luaContext.await( state, machine ) );
+        }
+        else
+        {
+            ComputerCraft.log.error( "Unknown method result " + future );
+            throw new LuaError( "Java Exception Thrown: Unknown method result" );
+        }
+    }
+
+    @Override
+    public Varargs resumeError( LuaState state, State context, LuaError error ) throws LuaError
+    {
+        state.debug.onReturn();
+        throw error;
+    }
+
+    private Varargs runFuture( LuaState state, State context, MethodResult future ) throws LuaError, UnwindThrowable
+    {
+        Deque<ILuaFunction> callbacks = context.callbacks;
+        while( true )
+        {
+            if( future instanceof MethodResult.AndThen )
+            {
+                MethodResult.AndThen then = ((MethodResult.AndThen) future);
+
+                // Thens are "unwrapped", being pushed onto a stack
+                if( callbacks == null ) callbacks = context.callbacks = new ArrayDeque<>();
+                callbacks.addLast( then.getCallback() );
+
+                future = then.getPrevious();
+            }
+            else if( future instanceof MethodResult.Immediate )
+            {
+                Object[] values = ((MethodResult.Immediate) future).getResult();
+
+                // Immediate values values will attempt to call the previous "then", or return if nothing 
+                // else needs to be done.
+                ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+                if( callback == null ) return machine.toValues( values );
+
+                future = runFunction( callback, values );
+            }
+            else if( future instanceof MethodResult.OnEvent )
+            {
+                MethodResult.OnEvent onEvent = (MethodResult.OnEvent) future;
+
+                // Mark this future as pending and yield
+                context.pending = future;
+                String filter = onEvent.getFilter();
+                LuaThread.yield( state, filter == null ? Constants.NIL : ValueFactory.valueOf( filter ) );
+                throw new IllegalStateException( "Unreachable" );
+            }
+            else if( future instanceof MethodResult.OnMainThread )
+            {
+                MethodResult.OnMainThread onMainThread = (MethodResult.OnMainThread) future;
+
+                // Mark this future as pending and yield
+                context.pending = future;
+                try
+                {
+                    context.taskId = callContext.issueMainThreadTask( () -> {
+                        context.taskResult = onMainThread.getTask().execute();
+                        return null;
+                    } );
+                }
+                catch( LuaException e )
+                {
+                    throw new LuaError( e.getMessage(), e.getLevel() );
+                }
+
+                LuaThread.yield( state, ValueFactory.valueOf( "task_complete" ) );
+                throw new IllegalStateException( "Unreachable" );
+            }
+            else if( future instanceof MethodResult.WithLuaContext )
+            {
+                MethodResult.WithLuaContext withContext = (MethodResult.WithLuaContext) future;
+
+                // Mark this future as pending and execute on a separate thread.
+                context.pending = future;
+                CobaltLuaContext luaContext = context.luaContext = new CobaltLuaContext( computer, state );
+                luaContext.execute( withContext.getConsumer() );
+                return runCallback( state, context, luaContext.await( state, machine ) );
+            }
+            else
+            {
+                ComputerCraft.log.error( "Unknown method result " + future );
+                throw new LuaError( "Java Exception Thrown: Unknown method result" );
+            }
+        }
+    }
+
+    private Varargs runCallback( LuaState state, State context, Object[] args ) throws LuaError, UnwindThrowable
+    {
+        Deque<ILuaFunction> callbacks = context.callbacks;
+        ILuaFunction callback = callbacks == null ? null : callbacks.pollLast();
+        if( callback == null ) return machine.toValues( args );
+
+        return runFuture( state, context, runFunction( callback, args ) );
+    }
+
+    private MethodResult runFunction( ILuaFunction func, Object[] args ) throws LuaError
+    {
+        MethodResult result;
+        try
+        {
+            result = func.call( args );
+        }
+        catch( LuaException e )
+        {
+            throw new LuaError( e.getMessage(), e.getLevel() );
+        }
+        catch( Exception e )
+        {
+            if( ComputerCraft.logPeripheralErrors )
+            {
+                ComputerCraft.log.error( "Error calling " + methodName + " on " + delegate, e );
+            }
+            throw new LuaError( "Java Exception Thrown: " + e.toString(), 0 );
+        }
+
+        if( result == null )
+        {
+            ComputerCraft.log.error( "Null result from " + func );
+            throw new LuaError( "Java Exception Thrown: Null result" );
+        }
+
+        return result;
+    }
+
+    static class State
+    {
+        Deque<ILuaFunction> callbacks;
+
+        MethodResult pending;
+
+        CobaltLuaContext luaContext;
+
+        long taskId;
+        MethodResult taskResult;
+    }
+}

src/main/java/dan200/computercraft/core/lua/Semaphore.java

@@ -0,0 +1,38 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.core.lua;
+
+/**
+ * A trivial way of signalling
+ */
+public final class Semaphore
+{
+    private volatile boolean state = false;
+
+    public synchronized void signal()
+    {
+        state = true;
+        notify();
+    }
+
+    public synchronized void await() throws InterruptedException
+    {
+        while( !state ) wait();
+        state = false;
+    }
+
+    public synchronized boolean await( long timeout ) throws InterruptedException
+    {
+        if( !state )
+        {
+            wait( timeout );
+            if( !state ) return false;
+        }
+        state = false;
+        return true;
+    }
+}

src/main/java/dan200/computercraft/core/terminal/Terminal.java

@@ -56,7 +56,7 @@ public class Terminal
         m_palette = new Palette();
     }
 
-    public void reset()
+    public synchronized void reset()
     {
         m_cursorColour = 0;
         m_cursorBackgroundColour = 15;
@@ -76,7 +76,7 @@ public class Terminal
         return m_height;
     }
     
-    public void resize( int width, int height )
+    public synchronized void resize( int width, int height )
     {
         if( width == m_width && height == m_height ) 
         {
@@ -189,7 +189,7 @@ public class Terminal
         return m_palette;
     }
 
-    public void blit( String text, String textColour, String backgroundColour )
+    public synchronized void blit( String text, String textColour, String backgroundColour )
     {
         int x = m_cursorX;
         int y = m_cursorY;
@@ -202,7 +202,7 @@ public class Terminal
         }
     }
 
-    public void write( String text )
+    public synchronized void write( String text )
     {
         int x = m_cursorX;
         int y = m_cursorY;
@@ -215,7 +215,7 @@ public class Terminal
         }
     }
     
-    public void scroll( int yDiff )
+    public synchronized void scroll( int yDiff )
     {
         if( yDiff != 0 )
         {
@@ -245,7 +245,7 @@ public class Terminal
         }
     }
     
-    public void clear()
+    public synchronized void clear()
     {
         for( int y = 0; y < m_height; ++y )
         {
@@ -256,7 +256,7 @@ public class Terminal
         m_changed = true;
     }
 
-    public void clearLine()
+    public synchronized void clearLine()
     {
         int y = m_cursorY;
         if( y >= 0 && y < m_height )
@@ -268,7 +268,7 @@ public class Terminal
         }
     }
         
-    public TextBuffer getLine( int y )
+    public synchronized TextBuffer getLine( int y )
     {
         if( y >= 0 && y < m_height )
         {
@@ -277,7 +277,7 @@ public class Terminal
         return null;
     }
 
-    public void setLine( int y, String text, String textColour, String backgroundColour )
+    public synchronized void setLine( int y, String text, String textColour, String backgroundColour )
     {
         m_text[y].write( text );
         m_textColour[y].write( textColour );
@@ -285,7 +285,7 @@ public class Terminal
         m_changed = true;
     }
     
-    public TextBuffer getTextColourLine( int y )
+    public synchronized TextBuffer getTextColourLine( int y )
     {
         if( y>=0 && y<m_height )
         {
@@ -294,7 +294,7 @@ public class Terminal
         return null;
     }
 
-    public TextBuffer getBackgroundColourLine( int y )
+    public synchronized TextBuffer getBackgroundColourLine( int y )
     {
         if( y>=0 && y<m_height )
         {
@@ -318,7 +318,7 @@ public class Terminal
         m_changed = false;
     }
 
-    public NBTTagCompound writeToNBT( NBTTagCompound nbttagcompound )
+    public synchronized NBTTagCompound writeToNBT( NBTTagCompound nbttagcompound )
     {
         nbttagcompound.setInteger( "term_cursorX", m_cursorX );
         nbttagcompound.setInteger( "term_cursorY", m_cursorY );
@@ -338,7 +338,7 @@ public class Terminal
         return nbttagcompound;
     }
 
-    public void readFromNBT( NBTTagCompound nbttagcompound )
+    public synchronized void readFromNBT( NBTTagCompound nbttagcompound )
     {
         m_cursorX = nbttagcompound.getInteger( "term_cursorX" );
         m_cursorY = nbttagcompound.getInteger( "term_cursorY" );

src/main/java/dan200/computercraft/core/tracking/ComputerTracker.java

@@ -0,0 +1,117 @@
+package dan200.computercraft.core.tracking;
+
+import dan200.computercraft.core.computer.Computer;
+import gnu.trove.map.hash.TObjectLongHashMap;
+
+import javax.annotation.Nullable;
+import java.lang.ref.WeakReference;
+
+public class ComputerTracker
+{
+    private final WeakReference<Computer> computer;
+    private final int computerId;
+
+    private long tasks;
+    private long totalTime;
+    private long maxTime;
+
+    private long serverCount;
+    private long serverTime;
+
+    private final TObjectLongHashMap<TrackingField> fields;
+
+    public ComputerTracker( Computer computer )
+    {
+        this.computer = new WeakReference<>( computer );
+        this.computerId = computer.getID();
+        this.fields = new TObjectLongHashMap<>();
+    }
+
+    ComputerTracker( ComputerTracker timings )
+    {
+        this.computer = timings.computer;
+        this.computerId = timings.computerId;
+
+        this.tasks = timings.tasks;
+        this.totalTime = timings.totalTime;
+        this.maxTime = timings.maxTime;
+
+        this.serverCount = timings.serverCount;
+        this.serverTime = timings.serverTime;
+
+        this.fields = new TObjectLongHashMap<>( timings.fields );
+    }
+
+    @Nullable
+    public Computer getComputer()
+    {
+        return computer.get();
+    }
+
+    public int getComputerId()
+    {
+        return computerId;
+    }
+
+    public long getTasks()
+    {
+        return tasks;
+    }
+
+    public long getTotalTime()
+    {
+        return totalTime;
+    }
+
+    public long getMaxTime()
+    {
+        return maxTime;
+    }
+
+    public long getAverage()
+    {
+        return totalTime / tasks;
+    }
+
+    void addTaskTiming( long time )
+    {
+        tasks++;
+        totalTime += time;
+        if( time > maxTime ) maxTime = time;
+    }
+
+    void addMainTiming( long time )
+    {
+        serverCount++;
+        serverTime += time;
+    }
+
+    void addValue( TrackingField field, long change )
+    {
+        synchronized( fields )
+        {
+            fields.adjustOrPutValue( field, change, change );
+        }
+    }
+
+    public long get( TrackingField field )
+    {
+        if( field == TrackingField.TASKS ) return tasks;
+        if( field == TrackingField.MAX_TIME ) return maxTime;
+        if( field == TrackingField.TOTAL_TIME ) return totalTime;
+        if( field == TrackingField.AVERAGE_TIME ) return tasks == 0 ? 0 : totalTime / tasks;
+
+        if( field == TrackingField.SERVER_COUNT ) return serverCount;
+        if( field == TrackingField.SERVER_TIME ) return serverTime;
+
+        synchronized( fields )
+        {
+            return fields.get( field );
+        }
+    }
+
+    public String getFormatted( TrackingField field )
+    {
+        return field.format( get( field ) );
+    }
+}

src/main/java/dan200/computercraft/core/tracking/Tracker.java

@@ -0,0 +1,49 @@
+package dan200.computercraft.core.tracking;
+
+import dan200.computercraft.core.computer.Computer;
+
+public interface Tracker
+{
+    @Deprecated
+    default void addTiming( Computer computer, long time )
+    {
+    }
+
+    /**
+     * Report how long a task executed on the computer thread took.
+     *
+     * Computer thread tasks include events or a computer being turned on/off.
+     *
+     * @param computer The computer processing this task
+     * @param time     The time taken for this task.
+     */
+    default void addTaskTiming( Computer computer, long time )
+    {
+        //noinspection deprecation
+        addTiming( computer, time );
+    }
+
+    /**
+     * Report how long a task executed on the server thread took.
+     *
+     * Server tasks include actions performed by peripherals.
+     *
+     * @param computer The computer processing this task
+     * @param time     The time taken for this task.
+     */
+    default void addServerTiming( Computer computer, long time )
+    {
+    }
+
+    /**
+     * Increment an arbitrary field by some value. Implementations may track how often this is called
+     * as well as the change, to compute some level of "average".
+     *
+     * @param computer The computer to increment
+     * @param field    The field to increment.
+     * @param change   The amount to increment said field by.
+     */
+    default void addValue( Computer computer, TrackingField field, long change )
+    {
+    }
+}

src/main/java/dan200/computercraft/core/tracking/Tracking.java

@@ -0,0 +1,80 @@
+package dan200.computercraft.core.tracking;
+
+import dan200.computercraft.core.computer.Computer;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Tracking
+{
+    static final AtomicInteger tracking = new AtomicInteger( 0 );
+
+    private static final Object lock = new Object();
+    private static final HashMap<UUID, TrackingContext> contexts = new HashMap<>();
+    private static final List<Tracker> trackers = new ArrayList<>();
+
+    public static TrackingContext getContext( UUID uuid )
+    {
+        synchronized( lock )
+        {
+            TrackingContext context = contexts.get( uuid );
+            if( context == null ) contexts.put( uuid, context = new TrackingContext() );
+            return context;
+        }
+    }
+
+    public static void add( Tracker tracker )
+    {
+        synchronized( lock )
+        {
+            trackers.add( tracker );
+            tracking.incrementAndGet();
+        }
+    }
+
+    public static void addTaskTiming( Computer computer, long time )
+    {
+        if( tracking.get() == 0 ) return;
+
+        synchronized( contexts )
+        {
+            for( TrackingContext context : contexts.values() ) context.addTaskTiming( computer, time );
+            for( Tracker tracker : trackers ) tracker.addTaskTiming( computer, time );
+        }
+    }
+
+    public static void addServerTiming( Computer computer, long time )
+    {
+        if( tracking.get() == 0 ) return;
+
+        synchronized( contexts )
+        {
+            for( TrackingContext context : contexts.values() ) context.addServerTiming( computer, time );
+            for( Tracker tracker : trackers ) tracker.addServerTiming( computer, time );
+        }
+    }
+
+    public static void addValue( Computer computer, TrackingField field, long change )
+    {
+        if( tracking.get() == 0 ) return;
+
+        synchronized( lock )
+        {
+            for( TrackingContext context : contexts.values() ) context.addValue( computer, field, change );
+            for( Tracker tracker : trackers ) tracker.addValue( computer, field, change );
+        }
+    }
+
+    public static void reset()
+    {
+        synchronized( lock )
+        {
+            contexts.clear();
+            trackers.clear();
+            tracking.set( 0 );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/tracking/TrackingContext.java

@@ -0,0 +1,111 @@
+package dan200.computercraft.core.tracking;
+
+import com.google.common.collect.MapMaker;
+import dan200.computercraft.core.computer.Computer;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Tracks timing information about computers, including how long they ran for
+ * and the number of events they handled.
+ *
+ * Note that this <em>will</em> track computers which have been deleted (hence
+ * the presence of {@link #timingLookup} and {@link #timings}
+ */
+public class TrackingContext implements Tracker
+{
+    private boolean tracking = false;
+
+    private final List<ComputerTracker> timings = new ArrayList<>();
+    private final Map<Computer, ComputerTracker> timingLookup = new MapMaker().weakKeys().makeMap();
+
+    public synchronized void start()
+    {
+        if( !tracking ) Tracking.tracking.incrementAndGet();
+        tracking = true;
+
+        timings.clear();
+        timingLookup.clear();
+    }
+
+    public synchronized boolean stop()
+    {
+        if( !tracking ) return false;
+
+        Tracking.tracking.decrementAndGet();
+        tracking = false;
+        timingLookup.clear();
+        return true;
+    }
+
+    public synchronized List<ComputerTracker> getImmutableTimings()
+    {
+        ArrayList<ComputerTracker> timings = new ArrayList<>( this.timings.size() );
+        for( ComputerTracker timing : this.timings ) timings.add( new ComputerTracker( timing ) );
+        return timings;
+    }
+
+    public synchronized List<ComputerTracker> getTimings()
+    {
+        return new ArrayList<>( timings );
+    }
+
+    @Override
+    public void addTaskTiming( Computer computer, long time )
+    {
+        if( !tracking ) return;
+
+        synchronized( this )
+        {
+            ComputerTracker computerTimings = timingLookup.get( computer );
+            if( computerTimings == null )
+            {
+                computerTimings = new ComputerTracker( computer );
+                timingLookup.put( computer, computerTimings );
+                timings.add( computerTimings );
+            }
+
+            computerTimings.addTaskTiming( time );
+        }
+    }
+
+    @Override
+    public void addServerTiming( Computer computer, long time )
+    {
+        if( !tracking ) return;
+
+        synchronized( this )
+        {
+            ComputerTracker computerTimings = timingLookup.get( computer );
+            if( computerTimings == null )
+            {
+                computerTimings = new ComputerTracker( computer );
+                timingLookup.put( computer, computerTimings );
+                timings.add( computerTimings );
+            }
+
+            computerTimings.addMainTiming( time );
+        }
+    }
+
+    @Override
+    public void addValue( Computer computer, TrackingField field, long change )
+    {
+        if( !tracking ) return;
+
+        synchronized( this )
+        {
+            ComputerTracker computerTimings = timingLookup.get( computer );
+            if( computerTimings == null )
+            {
+                computerTimings = new ComputerTracker( computer );
+                timingLookup.put( computer, computerTimings );
+                timings.add( computerTimings );
+            }
+
+            computerTimings.addValue( field, change );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/tracking/TrackingField.java

@@ -0,0 +1,88 @@
+package dan200.computercraft.core.tracking;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.LongFunction;
+
+public class TrackingField
+{
+    private static final Map<String, TrackingField> fields = new HashMap<>();
+
+    public static final TrackingField TASKS = TrackingField.of( "tasks", "Tasks", x -> String.format( "%4d", x ) );
+    public static final TrackingField TOTAL_TIME = TrackingField.of( "total", "Total time", x -> String.format( "%7.1fms", x / 1e6 ) );
+    public static final TrackingField AVERAGE_TIME = TrackingField.of( "average", "Average time", x -> String.format( "%4.1fms", x / 1e6 ) );
+    public static final TrackingField MAX_TIME = TrackingField.of( "max", "Max time", x -> String.format( "%5.1fms", x / 1e6 ) );
+
+    public static final TrackingField SERVER_COUNT = TrackingField.of( "server_count", "Server task count", x -> String.format( "%4d", x ) );
+    public static final TrackingField SERVER_TIME = TrackingField.of( "server_time", "Server task time", x -> String.format( "%7.1fms", x / 1e6 ) );
+
+    public static final TrackingField PERIPHERAL_OPS = TrackingField.of( "peripheral", "Peripheral calls", TrackingField::formatDefault );
+    public static final TrackingField FS_OPS = TrackingField.of( "fs", "Filesystem operations", TrackingField::formatDefault );
+    public static final TrackingField TURTLE_OPS = TrackingField.of( "turtle", "Turtle operations", TrackingField::formatDefault );
+
+    public static final TrackingField HTTP_REQUESTS = TrackingField.of( "http", "HTTP requests", TrackingField::formatDefault );
+    public static final TrackingField HTTP_UPLOAD = TrackingField.of( "http_upload", "HTTP upload", TrackingField::formatBytes );
+    public static final TrackingField HTTP_DOWNLOAD = TrackingField.of( "http_download", "HTTT download", TrackingField::formatBytes );
+
+    public static final TrackingField WEBSOCKET_INCOMING = TrackingField.of( "websocket_incoming", "Websocket incoming", TrackingField::formatBytes );
+    public static final TrackingField WEBSOCKET_OUTGOING = TrackingField.of( "websocket_outgoing", "Websocket outgoing", TrackingField::formatBytes );
+
+    private final String id;
+    private final String displayName;
+    private final LongFunction<String> format;
+
+    public String id()
+    {
+        return id;
+    }
+
+    public String displayName()
+    {
+        return displayName;
+    }
+
+    private TrackingField( String id, String displayName, LongFunction<String> format )
+    {
+        this.id = id;
+        this.displayName = displayName;
+        this.format = format;
+    }
+
+    public String format( long value )
+    {
+        return format.apply( value );
+    }
+
+    public static TrackingField of( String id, String displayName, LongFunction<String> format )
+    {
+        TrackingField field = new TrackingField( id, displayName, format );
+        fields.put( id, field );
+        return field;
+    }
+
+    public static Map<String, TrackingField> fields()
+    {
+        return Collections.unmodifiableMap( fields );
+    }
+
+    private static String formatDefault( long value )
+    {
+        return String.format( "%6d", value );
+    }
+
+    /**
+     * So technically a kibibyte, but let's not argue here.
+     */
+    private static final int KILOBYTE_SIZE = 1024;
+
+    private static final String SI_PREFIXES = "KMGT";
+
+    private static String formatBytes( long bytes )
+    {
+        if( bytes < 1024 ) return String.format( "%10d B", bytes );
+        int exp = (int) (Math.log( bytes ) / Math.log( KILOBYTE_SIZE ));
+        if( exp > SI_PREFIXES.length() ) exp = SI_PREFIXES.length();
+        return String.format( "%10.1f %siB", bytes / Math.pow( KILOBYTE_SIZE, exp ), SI_PREFIXES.charAt( exp - 1 ) );
+    }
+}

src/main/java/dan200/computercraft/shared/command/CommandComputerCraft.java

@@ -1,27 +1,40 @@
 package dan200.computercraft.shared.command;
 
-import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.computer.Computer;
+import dan200.computercraft.core.tracking.ComputerTracker;
+import dan200.computercraft.core.tracking.Tracking;
+import dan200.computercraft.core.tracking.TrackingContext;
+import dan200.computercraft.core.tracking.TrackingField;
 import dan200.computercraft.shared.command.framework.*;
 import dan200.computercraft.shared.computer.core.ServerComputer;
+import net.minecraft.command.CommandBase;
 import net.minecraft.command.CommandException;
 import net.minecraft.command.ICommandSender;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.player.EntityPlayerMP;
+import net.minecraft.server.MinecraftServer;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.text.ITextComponent;
+import net.minecraft.util.text.TextComponentString;
 import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
-import java.util.Collections;
-import java.util.List;
+import java.util.*;
+import java.util.function.Consumer;
 
 import static dan200.computercraft.shared.command.framework.ChatHelpers.*;
 
 public final class CommandComputerCraft extends CommandDelegate
 {
+    public static final UUID SYSTEM_UUID = new UUID( 0, 0 );
+
+    private static final int DUMP_LIST_ID = 5373952;
+    private static final int DUMP_SINGLE_ID = 1844510720;
+    private static final int TRACK_ID = 373882880;
+
     public CommandComputerCraft()
     {
         super( create() );
@@ -37,8 +50,8 @@ public final class CommandComputerCraft extends CommandDelegate
 
         root.register( new SubCommandBase(
             "dump", "[id]", "Display the status of computers.", UserLevel.OWNER_OP,
-            "Display the status of all computers or specific information about one computer. You can either specify the computer's instance " +
-                "id (e.g. 123) or computer id (e.g #123)."
+            "Display the status of all computers or specific information about one computer. You can specify the " +
+                "computer's instance id (e.g. 123), computer id (e.g #123) or label (e.g. \"@My Computer\")."
         )
         {
             @Override
@@ -46,19 +59,43 @@ public final class CommandComputerCraft extends CommandDelegate
             {
                 if( arguments.size() == 0 )
                 {
-                    TextTable table = new TextTable( "Instance", "Id", "On", "Position" );
+                    TextTable table = new TextTable( DUMP_LIST_ID, "Computer", "On", "Position" );
 
-                    int max = 50;
-                    for( ServerComputer computer : ComputerCraft.serverComputerRegistry.getComputers() )
+                    List<ServerComputer> computers = new ArrayList<>( ComputerCraft.serverComputerRegistry.getComputers() );
+
+                    // Unless we're on a server, limit the number of rows we can send.
+                    if( !(context.getSender() instanceof MinecraftServer) )
+                    {
+                        World world = context.getSender().getEntityWorld();
+                        BlockPos pos = context.getSender().getPosition();
+
+                        computers.sort( ( a, b ) -> {
+                            if( a.getWorld() == b.getWorld() && a.getWorld() == world )
+                            {
+                                return Double.compare( a.getPosition().distanceSq( pos ), b.getPosition().distanceSq( pos ) );
+                            }
+                            else if( a.getWorld() == world )
+                            {
+                                return -1;
+                            }
+                            else if( b.getWorld() == world )
+                            {
+                                return 1;
+                            }
+                            else
+                            {
+                                return Integer.compare( a.getInstanceID(), b.getInstanceID() );
+                            }
+                        } );
+                    }
+
+                    for( ServerComputer computer : computers )
                     {
                         table.addRow(
-                            linkComputer( computer ),
-                            text( Integer.toString( computer.getID() ) ),
+                            linkComputer( context, computer, computer.getID() ),
                             bool( computer.isOn() ),
                             linkPosition( context, computer )
                         );
-
-                        if( max-- < 0 ) break;
                     }
 
                     table.displayTo( context.getSender() );
@@ -67,7 +104,7 @@ public final class CommandComputerCraft extends CommandDelegate
                 {
                     ServerComputer computer = ComputerSelector.getComputer( arguments.get( 0 ) );
 
-                    TextTable table = new TextTable();
+                    TextTable table = new TextTable( DUMP_SINGLE_ID );
                     table.addRow( header( "Instance" ), text( Integer.toString( computer.getInstanceID() ) ) );
                     table.addRow( header( "Id" ), text( Integer.toString( computer.getID() ) ) );
                     table.addRow( header( "Label" ), text( computer.getLabel() ) );
@@ -80,7 +117,7 @@ public final class CommandComputerCraft extends CommandDelegate
                         IPeripheral peripheral = computer.getPeripheral( i );
                         if( peripheral != null )
                         {
-                            table.addRow( header( "Peripheral " + Computer.s_sideNames[ i ] ), text( peripheral.getType() ) );
+                            table.addRow( header( "Peripheral " + Computer.s_sideNames[i] ), text( peripheral.getType() ) );
                         }
                     }
 
@@ -98,39 +135,28 @@ public final class CommandComputerCraft extends CommandDelegate
             {
                 return arguments.size() == 1
                     ? ComputerSelector.completeComputer( arguments.get( 0 ) )
-                    : Collections.<String>emptyList();
+                    : Collections.emptyList();
             }
         } );
 
         root.register( new SubCommandBase(
             "shutdown", "[ids...]", "Shutdown computers remotely.", UserLevel.OWNER_OP,
-            "Shutdown the listed computers or all if none are specified. You can either specify the computer's instance " +
-                "id (e.g. 123) or computer id (e.g #123)."
+            "Shutdown the listed computers or all if none are specified. You can specify the computer's instance id " +
+                "(e.g. 123), computer id (e.g #123) or label (e.g. \"@My Computer\")."
         )
         {
             @Override
             public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments ) throws CommandException
             {
-                List<ServerComputer> computers = Lists.newArrayList();
-                if( arguments.size() > 0 )
-                {
-                    for( String arg : arguments )
+                withComputers( arguments, computers -> {
+                    int shutdown = 0;
+                    for( ServerComputer computer : computers )
                     {
-                        computers.add( ComputerSelector.getComputer( arg ) );
+                        if( computer.isOn() ) shutdown++;
+                        computer.unload();
                     }
-                }
-                else
-                {
-                    computers.addAll( ComputerCraft.serverComputerRegistry.getComputers() );
-                }
-
-                int shutdown = 0;
-                for( ServerComputer computer : computers )
-                {
-                    if( computer.isOn() ) shutdown++;
-                    computer.unload();
-                }
-                context.getSender().sendMessage( text( "Shutdown " + shutdown + " / " + computers.size() + " computers" ) );
+                    context.getSender().sendMessage( text( "Shutdown " + shutdown + " / " + computers.size() + " computers" ) );
+                } );
             }
 
             @Nonnull
@@ -138,7 +164,37 @@ public final class CommandComputerCraft extends CommandDelegate
             public List<String> getCompletion( @Nonnull CommandContext context, @Nonnull List<String> arguments )
             {
                 return arguments.size() == 0
-                    ? Collections.<String>emptyList()
+                    ? Collections.emptyList()
+                    : ComputerSelector.completeComputer( arguments.get( arguments.size() - 1 ) );
+            }
+        } );
+
+        root.register( new SubCommandBase(
+            "turn-on", "ids...", "Turn computers on remotely.", UserLevel.OWNER_OP,
+            "Turn on the listed computers. You can specify the computer's instance id (e.g. 123), computer id (e.g #123) " +
+                "or label (e.g. \"@My Computer\")."
+        )
+        {
+            @Override
+            public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments ) throws CommandException
+            {
+                withComputers( arguments, computers -> {
+                    int on = 0;
+                    for( ServerComputer computer : computers )
+                    {
+                        if( !computer.isOn() ) on++;
+                        computer.turnOn();
+                    }
+                    context.getSender().sendMessage( text( "Turned on " + on + " / " + computers.size() + " computers" ) );
+                } );
+            }
+
+            @Nonnull
+            @Override
+            public List<String> getCompletion( @Nonnull CommandContext context, @Nonnull List<String> arguments )
+            {
+                return arguments.size() == 0
+                    ? Collections.emptyList()
                     : ComputerSelector.completeComputer( arguments.get( arguments.size() - 1 ) );
             }
         } );
@@ -194,48 +250,179 @@ public final class CommandComputerCraft extends CommandDelegate
             {
                 return arguments.size() == 1
                     ? ComputerSelector.completeComputer( arguments.get( 0 ) )
-                    : Collections.<String>emptyList();
+                    : Collections.emptyList();
             }
         } );
 
-        root.register(new SubCommandBase(
+        root.register( new SubCommandBase(
             "view", "<id>", "View the terminal of a computer.", UserLevel.OP,
             "Open the terminal of a computer, allowing remote control of a computer. This does not provide access to " +
                 "turtle's inventories. You can either specify the computer's instance id (e.g. 123) or computer id (e.g #123)."
-        ) {
+        )
+        {
             @Override
-            public void execute(@Nonnull CommandContext context, @Nonnull List<String> arguments) throws CommandException {
-                if (arguments.size() != 1) throw new CommandException(context.getFullUsage());
+            public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments ) throws CommandException
+            {
+                if( arguments.size() != 1 ) throw new CommandException( context.getFullUsage() );
 
                 ICommandSender sender = context.getSender();
-                if (!(sender instanceof EntityPlayerMP)) {
-                    throw new CommandException("Cannot open terminal for non-player");
+                if( !(sender instanceof EntityPlayerMP) )
+                {
+                    throw new CommandException( "Cannot open terminal for non-player" );
                 }
 
-                ServerComputer computer = ComputerSelector.getComputer(arguments.get(0));
+                ServerComputer computer = ComputerSelector.getComputer( arguments.get( 0 ) );
                 ComputerCraft.openComputerGUI( (EntityPlayerMP) sender, computer );
             }
 
             @Nonnull
             @Override
-            public List<String> getCompletion(@Nonnull CommandContext context, @Nonnull List<String> arguments) {
+            public List<String> getCompletion( @Nonnull CommandContext context, @Nonnull List<String> arguments )
+            {
                 return arguments.size() == 1
                     ? ComputerSelector.completeComputer( arguments.get( 0 ) )
                     : Collections.emptyList();
             }
-        });
+        } );
+
+        CommandRoot track = new CommandRoot( "track", "Track execution times for computers.",
+            "Track how long computers execute for, as well as how many events they handle. This presents information in " +
+                "a similar way to /forge track and can be useful for diagnosing lag." );
+        root.register( track );
+
+        track.register( new SubCommandBase(
+            "start", "Start tracking all computers", UserLevel.OWNER_OP,
+            "Start tracking all computers' execution times and event counts. This will discard the results of previous runs."
+        )
+        {
+            @Override
+            public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments )
+            {
+                getTimingContext( context ).start();
+
+                String stopCommand = "/" + context.parent().getFullPath() + " stop";
+                context.getSender().sendMessage( list(
+                    text( "Run " ),
+                    link( text( stopCommand ), stopCommand, "Click to stop tracking" ),
+                    text( " to stop tracking and view the results" )
+                ) );
+            }
+        } );
+
+        track.register( new SubCommandBase(
+            "stop", "Stop tracking all computers", UserLevel.OWNER_OP,
+            "Stop tracking all computers' events and execution times"
+        )
+        {
+            @Override
+            public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments ) throws CommandException
+            {
+                TrackingContext timings = getTimingContext( context );
+                if( !timings.stop() ) throw new CommandException( "Tracking not enabled" );
+                displayTimings( context, timings.getImmutableTimings(), TrackingField.AVERAGE_TIME );
+            }
+        } );
+
+        track.register( new SubCommandBase(
+            "dump", "[kind]", "Dump the latest track results", UserLevel.OWNER_OP,
+            "Dump the latest results of computer tracking."
+        )
+        {
+            @Override
+            public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments ) throws CommandException
+            {
+                TrackingField field = TrackingField.AVERAGE_TIME;
+                if( arguments.size() >= 1 )
+                {
+                    field = TrackingField.fields().get( arguments.get( 0 ) );
+                    if( field == null ) throw new CommandException( "Unknown field '" + arguments.get( 0 ) + "'" );
+                }
+
+                displayTimings( context, getTimingContext( context ).getImmutableTimings(), field );
+            }
+
+            @Nonnull
+            @Override
+            public List<String> getCompletion( @Nonnull CommandContext context, @Nonnull List<String> arguments )
+            {
+                if( arguments.size() == 1 )
+                {
+                    String match = arguments.get( 0 );
+
+                    List<String> out = new ArrayList<>();
+                    for( String key : TrackingField.fields().keySet() )
+                    {
+                        if( CommandBase.doesStringStartWith( match, key ) ) out.add( key );
+                    }
+
+                    out.sort( Comparator.naturalOrder() );
+                    return out;
+                }
+                else
+                {
+                    return super.getCompletion( context, arguments );
+                }
+            }
+        } );
+
+        root.register( new SubCommandBase(
+            "reload", "Reload the ComputerCraft config file", UserLevel.OWNER_OP,
+            "Reload the ComputerCraft config file"
+        )
+        {
+            @Override
+            public void execute( @Nonnull CommandContext context, @Nonnull List<String> arguments )
+            {
+                ComputerCraft.loadConfig();
+                ComputerCraft.syncConfig();
+                context.getSender().sendMessage( new TextComponentString( "Reloaded config" ) );
+            }
+        } );
 
 
         return root;
     }
 
-    private static ITextComponent linkComputer( ServerComputer computer )
+    private static ITextComponent linkComputer( CommandContext context, ServerComputer serverComputer, int computerId )
     {
-        return link(
-            text( Integer.toString( computer.getInstanceID() ) ),
-            "/computercraft dump " + computer.getInstanceID(),
-            "View more info about this computer"
-        );
+        ITextComponent out = new TextComponentString( "" );
+
+        // Append the computer instance
+        if( serverComputer == null )
+        {
+            out.appendSibling( text( "?" ) );
+        }
+        else
+        {
+            out.appendSibling( link(
+                text( Integer.toString( serverComputer.getInstanceID() ) ),
+                "/computercraft dump " + serverComputer.getInstanceID(),
+                "View more info about this computer"
+            ) );
+        }
+
+        // And ID
+        out.appendText( " (id " + computerId + ")" );
+
+        // And, if we're a player, some useful links
+        if( serverComputer != null && UserLevel.OP.canExecute( context ) && context.fromPlayer() )
+        {
+            out
+                .appendText( " " )
+                .appendSibling( link(
+                    text( "\u261b" ),
+                    "/computercraft tp " + serverComputer.getInstanceID(),
+                    "Teleport to this computer"
+                ) )
+                .appendText( " " )
+                .appendSibling( link(
+                    text( "\u20e2" ),
+                    "/computercraft view " + serverComputer.getInstanceID(),
+                    "View this computer"
+                ) );
+        }
+
+        return out;
     }
 
     private static ITextComponent linkPosition( CommandContext context, ServerComputer computer )
@@ -253,4 +440,93 @@ public final class CommandComputerCraft extends CommandDelegate
             return position( computer.getPosition() );
         }
     }
+
+    private static TrackingContext getTimingContext( CommandContext context )
+    {
+        Entity entity = context.getSender().getCommandSenderEntity();
+        if( entity instanceof EntityPlayerMP )
+        {
+            return Tracking.getContext( entity.getUniqueID() );
+        }
+        else
+        {
+            return Tracking.getContext( SYSTEM_UUID );
+        }
+    }
+
+    private static void displayTimings( CommandContext context, List<ComputerTracker> timings, TrackingField field ) throws CommandException
+    {
+        if( timings.isEmpty() ) throw new CommandException( "No timings available" );
+
+        Map<Computer, ServerComputer> lookup = new HashMap<>();
+        int maxId = 0, maxInstance = 0;
+        for( ServerComputer server : ComputerCraft.serverComputerRegistry.getComputers() )
+        {
+            lookup.put( server.getComputer(), server );
+
+            if( server.getInstanceID() > maxInstance ) maxInstance = server.getInstanceID();
+            if( server.getID() > maxId ) maxId = server.getID();
+        }
+
+        timings.sort( Comparator.<ComputerTracker, Long>comparing( x -> x.get( field ) ).reversed() );
+
+        boolean defaultLayout = field == TrackingField.TASKS || field == TrackingField.TOTAL_TIME
+            || field == TrackingField.AVERAGE_TIME || field == TrackingField.MAX_TIME;
+
+
+        TextTable table = defaultLayout
+            ? new TextTable( TRACK_ID, "Computer", "Tasks", "Total", "Average", "Maximum" )
+            : new TextTable( TRACK_ID, "Computer", field.displayName() );
+
+        for( ComputerTracker entry : timings )
+        {
+            Computer computer = entry.getComputer();
+            ServerComputer serverComputer = computer == null ? null : lookup.get( computer );
+
+            ITextComponent computerComponent = linkComputer( context, serverComputer, entry.getComputerId() );
+
+            if( defaultLayout )
+            {
+                table.addRow(
+                    computerComponent,
+                    text( entry.getFormatted( TrackingField.TASKS ) ),
+                    text( entry.getFormatted( TrackingField.TOTAL_TIME ) ),
+                    text( entry.getFormatted( TrackingField.AVERAGE_TIME ) ),
+                    text( entry.getFormatted( TrackingField.MAX_TIME ) )
+                );
+            }
+            else
+            {
+                table.addRow( computerComponent, text( entry.getFormatted( field ) ) );
+            }
+        }
+
+        table.displayTo( context.getSender() );
+    }
+
+    private static void withComputers( List<String> selectors, Consumer<Collection<ServerComputer>> action ) throws CommandException
+    {
+        Set<ServerComputer> computers = Sets.newHashSet();
+        List<String> failed = new ArrayList<>();
+        if( selectors.isEmpty() )
+        {
+            computers.addAll( ComputerCraft.serverComputerRegistry.getComputers() );
+        }
+        else
+        {
+            for( String selector : selectors )
+            {
+                List<ServerComputer> selected = ComputerSelector.getComputers( selector );
+                computers.addAll( selected );
+                if( selected.isEmpty() ) failed.add( selector );
+            }
+        }
+
+        action.accept( computers );
+
+        if( !failed.isEmpty() )
+        {
+            throw new CommandException( "Could not find computers matching " + String.join( ", ", failed ) );
+        }
+    }
 }

src/main/java/dan200/computercraft/shared/command/ComputerSelector.java

@@ -3,15 +3,51 @@ package dan200.computercraft.shared.command;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
 import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.shared.computer.core.ComputerFamily;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import net.minecraft.command.CommandException;
 
-import java.util.List;
-import java.util.Set;
+import java.util.*;
+import java.util.function.Predicate;
 
 public final class ComputerSelector
 {
+    private static List<ServerComputer> getComputers( Predicate<ServerComputer> predicate ) throws CommandException
+    {
+        // We copy it to prevent concurrent modifications.
+        ArrayList<ServerComputer> computers = new ArrayList<>( ComputerCraft.serverComputerRegistry.getComputers() );
+        computers.removeIf( predicate.negate() );
+        return computers;
+    }
+
     public static ServerComputer getComputer( String selector ) throws CommandException
+    {
+        List<ServerComputer> computers = getComputers( selector );
+        if( computers.size() == 0 )
+        {
+            throw new CommandException( "No computer matching " + selector );
+        }
+        else if( computers.size() == 1 )
+        {
+            return computers.get( 0 );
+        }
+        else
+        {
+            StringBuilder builder = new StringBuilder( "Multiple computers matching " )
+                .append( selector ).append( " (instances " );
+
+            for( int i = 0; i < computers.size(); i++ )
+            {
+                if( i > 0 ) builder.append( ", " );
+                builder.append( computers.get( i ).getInstanceID() );
+            }
+            builder.append( ")" );
+
+            throw new CommandException( builder.toString() );
+        }
+    }
+
+    public static List<ServerComputer> getComputers( String selector ) throws CommandException
     {
         if( selector.length() > 0 && selector.charAt( 0 ) == '#' )
         {
@@ -27,49 +63,17 @@ public final class ComputerSelector
                 throw new CommandException( "'" + selector + "' is not a valid number" );
             }
 
-            // We copy it to prevent concurrent modifications.
-            List<ServerComputer> computers = Lists.newArrayList( ComputerCraft.serverComputerRegistry.getComputers() );
-            List<ServerComputer> candidates = Lists.newArrayList();
-            for( ServerComputer searchComputer : computers )
-            {
-                if( searchComputer.getID() == id )
-                {
-                    candidates.add( searchComputer );
-                }
-            }
-
-            if( candidates.size() == 0 )
-            {
-                throw new CommandException( "No such computer for id " + id );
-            }
-            else if( candidates.size() == 1 )
-            {
-                return candidates.get( 0 );
-            }
-            else
-            {
-                StringBuilder builder = new StringBuilder( "Multiple computers with id " )
-                    .append( id ).append( " (instances " );
-
-                boolean first = true;
-                for( ServerComputer computer : candidates )
-                {
-                    if( first )
-                    {
-                        first = false;
-                    }
-                    else
-                    {
-                        builder.append( ", " );
-                    }
-
-                    builder.append( computer.getInstanceID() );
-                }
-
-                builder.append( ")" );
-
-                throw new CommandException( builder.toString() );
-            }
+            return getComputers( x -> x.getID() == id );
+        }
+        else if( selector.length() > 0 && selector.charAt( 0 ) == '@' )
+        {
+            String label = selector.substring( 1 );
+            return getComputers( x -> Objects.equals( label, x.getLabel() ) );
+        }
+        else if( selector.length() > 0 && selector.charAt( 0 ) == '~' )
+        {
+            String familyName = selector.substring( 1 );
+            return getComputers( x -> x.getFamily().name().equalsIgnoreCase( familyName ) );
         }
         else
         {
@@ -84,20 +88,13 @@ public final class ComputerSelector
             }
 
             ServerComputer computer = ComputerCraft.serverComputerRegistry.get( instance );
-            if( computer == null )
-            {
-                throw new CommandException( "No such computer for instance id " + instance );
-            }
-            else
-            {
-                return computer;
-            }
+            return computer == null ? Collections.emptyList() : Collections.singletonList( computer );
         }
     }
 
     public static List<String> completeComputer( String selector )
     {
-        Set<String> options = Sets.newHashSet();
+        TreeSet<String> options = Sets.newTreeSet();
 
         // We copy it to prevent concurrent modifications.
         List<ServerComputer> computers = Lists.newArrayList( ComputerCraft.serverComputerRegistry.getComputers() );
@@ -112,6 +109,26 @@ public final class ComputerSelector
                 if( id.startsWith( selector ) ) options.add( "#" + id );
             }
         }
+        else if( selector.length() > 0 && selector.charAt( 0 ) == '@' )
+        {
+            String label = selector.substring( 1 );
+            for( ServerComputer computer : computers )
+            {
+                String thisLabel = computer.getLabel();
+                if( thisLabel != null && thisLabel.startsWith( label ) ) options.add( "@" + thisLabel );
+            }
+        }
+        else if( selector.length() > 0 && selector.charAt( 0 ) == '~' )
+        {
+            String familyName = selector.substring( 1 ).toLowerCase( Locale.ENGLISH );
+            for( ComputerFamily family : ComputerFamily.values() )
+            {
+                if( family.name().toLowerCase( Locale.ENGLISH ).startsWith( familyName ) )
+                {
+                    options.add( "~" + family.name() );
+                }
+            }
+        }
         else
         {
             for( ServerComputer computer : computers )
@@ -121,6 +138,20 @@ public final class ComputerSelector
             }
         }
 
-        return Lists.newArrayList( options );
+        if( options.size() > 100 )
+        {
+            ArrayList<String> result = Lists.newArrayListWithCapacity( 100 );
+            for( String element : options )
+            {
+                if( result.size() > 100 ) break;
+                result.add( element );
+            }
+
+            return result;
+        }
+        else
+        {
+            return Lists.newArrayList( options );
+        }
     }
 }

src/main/java/dan200/computercraft/shared/command/framework/CommandContext.java

@@ -2,7 +2,9 @@ package dan200.computercraft.shared.command.framework;
 
 import com.google.common.collect.Lists;
 import net.minecraft.command.ICommandSender;
+import net.minecraft.entity.player.EntityPlayerMP;
 import net.minecraft.server.MinecraftServer;
+import net.minecraftforge.common.util.FakePlayer;
 
 import java.util.Collections;
 import java.util.List;
@@ -90,4 +92,9 @@ public final class CommandContext
     {
         return sender;
     }
+
+    public boolean fromPlayer()
+    {
+        return sender instanceof EntityPlayerMP && !(sender instanceof FakePlayer);
+    }
 }

src/main/java/dan200/computercraft/shared/command/framework/CommandDelegate.java

@@ -36,7 +36,7 @@ public class CommandDelegate implements ICommand
     @Override
     public String getUsage( @Nonnull ICommandSender sender )
     {
-        return "/" + command.getName() + " " + command.getUsage( new CommandContext( sender.getServer(), sender, command ) );
+        return new CommandContext( sender.getServer(), sender, command ).getFullUsage();
     }
 
     @Nonnull

src/main/java/dan200/computercraft/shared/command/framework/CommandRoot.java

@@ -86,7 +86,7 @@ public class CommandRoot implements ISubCommand
     {
         for( ISubCommand command : subCommands.values() )
         {
-            if( command.checkPermission( context ) ) return true;
+            if( !(command instanceof SubCommandHelp) && command.checkPermission( context ) ) return true;
         }
         return false;
     }
@@ -108,7 +108,7 @@ public class CommandRoot implements ISubCommand
             ISubCommand command = subCommands.get( arguments.get( 0 ) );
             if( command == null || !command.checkPermission( context ) )
             {
-                throw new CommandException( getName() + " " + getUsage( context ) );
+                throw new CommandException( context.getFullUsage() );
             }
 
             command.execute( context.enter( command ), arguments.subList( 1, arguments.size() ) );

src/main/java/dan200/computercraft/shared/command/framework/TextFormatter.java

@@ -0,0 +1,147 @@
+package dan200.computercraft.shared.command.framework;
+
+import net.minecraft.command.ICommandSender;
+import net.minecraft.entity.player.EntityPlayerMP;
+import net.minecraft.util.text.ITextComponent;
+import net.minecraft.util.text.TextComponentString;
+import net.minecraft.util.text.TextFormatting;
+import net.minecraftforge.common.util.FakePlayer;
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.Arrays;
+
+import static dan200.computercraft.shared.command.framework.ChatHelpers.coloured;
+
+/**
+ * Adapated from Sponge's PaginationCalculator
+ */
+public class TextFormatter
+{
+    private static final char PADDING_CHAR = '\u02cc';
+
+    /**
+     * Yoinked from FontRenderer
+     *
+     * @see net.minecraft.client.gui.FontRenderer#charWidth
+     * @see net.minecraft.client.gui.FontRenderer#getCharWidth(char)
+     */
+    private static final String CHARACTERS = "\u00c0\u00c1\u00c2\u00c8\u00ca\u00cb\u00cd\u00d3\u00d4\u00d5\u00da\u00df\u00e3\u00f5\u011f\u0130\u0131\u0152\u0153\u015e\u015f\u0174\u0175\u017e\u0207\u0000\u0000\u0000\u0000\u0000\u0000\u0000 !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\u0000\u00c7\u00fc\u00e9\u00e2\u00e4\u00e0\u00e5\u00e7\u00ea\u00eb\u00e8\u00ef\u00ee\u00ec\u00c4\u00c5\u00c9\u00e6\u00c6\u00f4\u00f6\u00f2\u00fb\u00f9\u00ff\u00d6\u00dc\u00f8\u00a3\u00d8\u00d7\u0192\u00e1\u00ed\u00f3\u00fa\u00f1\u00d1\u00aa\u00ba\u00bf\u00ae\u00ac\u00bd\u00bc\u00a1\u00ab\u00bb\u2591\u2592\u2593\u2502\u2524\u2561\u2562\u2556\u2555\u2563\u2551\u2557\u255d\u255c\u255b\u2510\u2514\u2534\u252c\u251c\u2500\u253c\u255e\u255f\u255a\u2554\u2569\u2566\u2560\u2550\u256c\u2567\u2568\u2564\u2565\u2559\u2558\u2552\u2553\u256b\u256a\u2518\u250c\u2588\u2584\u258c\u2590\u2580\u03b1\u03b2\u0393\u03c0\u03a3\u03c3\u03bc\u03c4\u03a6\u0398\u03a9\u03b4\u221e\u2205\u2208\u2229\u2261\u00b1\u2265\u2264\u2320\u2321\u00f7\u2248\u00b0\u2219\u00b7\u221a\u207f\u00b2\u25a0\u0000";
+    private static final int[] CHAR_WIDTHS = new int[]{
+        6, 6, 6, 6, 6, 6, 4, 6, 6, 6, 6, 6, 6, 6, 6, 4,
+        4, 6, 7, 6, 6, 6, 6, 6, 6, 1, 1, 1, 1, 1, 1, 1,
+        1, 2, 5, 6, 6, 6, 6, 3, 5, 5, 5, 6, 2, 6, 2, 6,
+        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 2, 2, 5, 6, 5, 6,
+        7, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6, 6, 6, 6, 6, 6,
+        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6, 4, 6, 6,
+        3, 6, 6, 6, 6, 6, 5, 6, 6, 2, 6, 5, 3, 6, 6, 6,
+        6, 6, 6, 6, 4, 6, 6, 6, 6, 6, 6, 5, 2, 5, 7, 6,
+        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6, 3, 6, 6,
+        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6,
+        6, 3, 6, 6, 6, 6, 6, 6, 6, 7, 6, 6, 6, 2, 6, 6,
+        8, 9, 9, 6, 6, 6, 8, 8, 6, 8, 8, 8, 8, 8, 6, 6,
+        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
+        9, 9, 9, 9, 9, 9, 9, 9, 9, 6, 9, 9, 9, 5, 9, 9,
+        8, 7, 7, 8, 7, 8, 8, 8, 7, 8, 8, 7, 9, 9, 6, 7,
+        7, 7, 7, 7, 9, 6, 7, 8, 7, 6, 6, 9, 7, 6, 7, 1
+    };
+
+    private static final int[] EXTRA_CHARS = new int[]{
+        '\u20e2', '\u261b',
+    };
+
+    private static final byte[] EXTRA_WIDTHS = new byte[]{
+        8, 4,
+    };
+
+    public static int getWidth( int codePoint )
+    {
+        // Escape codes
+        if( codePoint == 167 ) return -1;
+
+        // Space and non-breaking space
+        if( codePoint == 32 || codePoint == 160 ) return 4;
+
+        // Built-in characters
+        int nonUnicodeIdx = CHARACTERS.indexOf( codePoint );
+        if( codePoint > 0 && nonUnicodeIdx != -1 ) return CHAR_WIDTHS[nonUnicodeIdx];
+
+        // Other special characters we use.
+        int extraIdx = Arrays.binarySearch( EXTRA_CHARS, codePoint );
+        if( extraIdx >= 0 ) return EXTRA_WIDTHS[extraIdx];
+
+        return 0;
+    }
+
+    public static int getWidth( ITextComponent component )
+    {
+        int total = 0;
+        if( component instanceof TextComponentString )
+        {
+            String contents = component.getUnformattedComponentText();
+
+            int bold = component.getStyle().getBold() ? 1 : 0;
+            for( int i = 0; i < contents.length(); i++ )
+            {
+                int cp = contents.charAt( i );
+                assert cp != '\n';
+                int width = getWidth( cp );
+                if( width < 0 )
+                {
+                    i++;
+                }
+                else
+                {
+                    total += width + bold;
+                }
+            }
+        }
+
+        for( ITextComponent child : component.getSiblings() )
+        {
+            total += getWidth( child );
+        }
+
+        return total;
+    }
+
+    public static boolean isPlayer( ICommandSender sender )
+    {
+        return sender instanceof EntityPlayerMP && !(sender instanceof FakePlayer);
+    }
+
+    public static int getMaxWidth( ICommandSender sender )
+    {
+        return isPlayer( sender ) ? 320 : 80;
+    }
+
+    public static int getWidthFor( ITextComponent component, ICommandSender sender )
+    {
+        return isPlayer( sender ) ? getWidth( component ) : component.getUnformattedText().length();
+    }
+
+    public static int getWidthFor( int codepoint, ICommandSender sender )
+    {
+        return isPlayer( sender ) ? getWidth( codepoint ) : 1;
+    }
+
+    public static void appendFixedWidth( ITextComponent out, ICommandSender sender, ITextComponent entry, int maxWidth )
+    {
+        out.appendSibling( entry );
+
+        int width = getWidthFor( entry, sender );
+        int delta = maxWidth - width;
+
+        int spaceWidth = getWidthFor( ' ', sender );
+        int spaces = delta / spaceWidth;
+        int extra = delta % spaces;
+
+        // Append a fixed number of spaces
+        if( spaces > 0 ) out.appendSibling( new TextComponentString( StringUtils.repeat( ' ', spaces ) ) );
+
+        // Append several minor characters to pad to a full string 
+        if( extra > 0 )
+        {
+            out.appendSibling( coloured( StringUtils.repeat( PADDING_CHAR, extra ), TextFormatting.GRAY ) );
+        }
+    }
+}

src/main/java/dan200/computercraft/shared/command/framework/TextTable.java

@@ -1,117 +1,53 @@
 package dan200.computercraft.shared.command.framework;
 
 import com.google.common.collect.Lists;
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.shared.network.ComputerCraftPacket;
 import net.minecraft.command.ICommandSender;
 import net.minecraft.entity.player.EntityPlayerMP;
 import net.minecraft.util.text.ITextComponent;
 import net.minecraft.util.text.TextComponentString;
 import net.minecraft.util.text.TextFormatting;
-import net.minecraftforge.common.util.FakePlayer;
 import org.apache.commons.lang3.StringUtils;
 
 import javax.annotation.Nonnull;
+import java.util.ArrayList;
 import java.util.List;
 
 import static dan200.computercraft.shared.command.framework.ChatHelpers.coloured;
 import static dan200.computercraft.shared.command.framework.ChatHelpers.text;
+import static dan200.computercraft.shared.command.framework.TextFormatter.*;
 
 public class TextTable
 {
-    private static final String CHARACTERS = "\u00c0\u00c1\u00c2\u00c8\u00ca\u00cb\u00cd\u00d3\u00d4\u00d5\u00da\u00df\u00e3\u00f5\u011f\u0130\u0131\u0152\u0153\u015e\u015f\u0174\u0175\u017e\u0207\u0000\u0000\u0000\u0000\u0000\u0000\u0000 !\"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\u0000\u00c7\u00fc\u00e9\u00e2\u00e4\u00e0\u00e5\u00e7\u00ea\u00eb\u00e8\u00ef\u00ee\u00ec\u00c4\u00c5\u00c9\u00e6\u00c6\u00f4\u00f6\u00f2\u00fb\u00f9\u00ff\u00d6\u00dc\u00f8\u00a3\u00d8\u00d7\u0192\u00e1\u00ed\u00f3\u00fa\u00f1\u00d1\u00aa\u00ba\u00bf\u00ae\u00ac\u00bd\u00bc\u00a1\u00ab\u00bb\u2591\u2592\u2593\u2502\u2524\u2561\u2562\u2556\u2555\u2563\u2551\u2557\u255d\u255c\u255b\u2510\u2514\u2534\u252c\u251c\u2500\u253c\u255e\u255f\u255a\u2554\u2569\u2566\u2560\u2550\u256c\u2567\u2568\u2564\u2565\u2559\u2558\u2552\u2553\u256b\u256a\u2518\u250c\u2588\u2584\u258c\u2590\u2580\u03b1\u03b2\u0393\u03c0\u03a3\u03c3\u03bc\u03c4\u03a6\u0398\u03a9\u03b4\u221e\u2205\u2208\u2229\u2261\u00b1\u2265\u2264\u2320\u2321\u00f7\u2248\u00b0\u2219\u00b7\u221a\u207f\u00b2\u25a0\u0000";
-    private static final int[] CHAR_WIDTHS = new int[] {
-        6, 6, 6, 6, 6, 6, 4, 6, 6, 6, 6, 6, 6, 6, 6, 4,
-        4, 6, 7, 6, 6, 6, 6, 6, 6, 1, 1, 1, 1, 1, 1, 1,
-        1, 2, 5, 6, 6, 6, 6, 3, 5, 5, 5, 6, 2, 6, 2, 6,
-        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 2, 2, 5, 6, 5, 6,
-        7, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6, 6, 6, 6, 6, 6,
-        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6, 4, 6, 6,
-        3, 6, 6, 6, 6, 6, 5, 6, 6, 2, 6, 5, 3, 6, 6, 6,
-        6, 6, 6, 6, 4, 6, 6, 6, 6, 6, 6, 5, 2, 5, 7, 6,
-        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6, 3, 6, 6,
-        6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6,
-        6, 3, 6, 6, 6, 6, 6, 6, 6, 7, 6, 6, 6, 2, 6, 6,
-        8, 9, 9, 6, 6, 6, 8, 8, 6, 8, 8, 8, 8, 8, 6, 6,
-        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
-        9, 9, 9, 9, 9, 9, 9, 9, 9, 6, 9, 9, 9, 5, 9, 9,
-        8, 7, 7, 8, 7, 8, 8, 8, 7, 8, 8, 7, 9, 9, 6, 7,
-        7, 7, 7, 7, 9, 6, 7, 8, 7, 6, 6, 9, 7, 6, 7, 1
-    };
-
-    private static final ITextComponent SEPARATOR = coloured( " | ", TextFormatting.GRAY );
+    private static final ITextComponent SEPARATOR = coloured( "| ", TextFormatting.GRAY );
     private static final ITextComponent LINE = text( "\n" );
 
-    private static int getWidth( char character, ICommandSender sender )
-    {
-        if( sender instanceof EntityPlayerMP && !(sender instanceof FakePlayer) )
-        {
-            // Use font widths here.
-            if( character == 167 )
-            {
-                return -1;
-            }
-            else if( character == 32 )
-            {
-                return 4;
-            }
-            else if( CHARACTERS.indexOf( character ) != -1 )
-            {
-                return CHAR_WIDTHS[ character ];
-            }
-            else
-            {
-                // Eh, close enough.
-                return 6;
-            }
-        }
-        else
-        {
-            return 1;
-        }
-    }
-
-    private static int getWidth( ITextComponent text, ICommandSender sender )
-    {
-        int sum = 0;
-        String chars = text.getUnformattedText();
-        for( int i = 0; i < chars.length(); i++ )
-        {
-            sum += getWidth( chars.charAt( i ), sender );
-        }
-
-        return sum;
-    }
-
-    private static boolean isPlayer( ICommandSender sender )
-    {
-        return sender instanceof EntityPlayerMP && !(sender instanceof FakePlayer);
-    }
-
-    private static int getMaxWidth( ICommandSender sender )
-    {
-        return isPlayer( sender ) ? 320 : 80;
-    }
-
+    private final int id;
     private int columns = -1;
     private final ITextComponent[] header;
     private final List<ITextComponent[]> rows = Lists.newArrayList();
 
-    public TextTable( @Nonnull ITextComponent... header )
+    public TextTable( int id, @Nonnull ITextComponent... header )
     {
+        this.id = id;
         this.header = header;
         this.columns = header.length;
     }
 
-    public TextTable()
+    public TextTable( int id )
     {
-        header = null;
+        this.id = id;
+        this.header = null;
     }
 
-    public TextTable( @Nonnull String... header )
+    public TextTable( int id, @Nonnull String... header )
     {
-        this.header = new ITextComponent[ header.length ];
+        this.id = id;
+        this.header = new ITextComponent[header.length];
         for( int i = 0; i < header.length; i++ )
         {
-            this.header[ i ] = ChatHelpers.header( header[ i ] );
+            this.header[i] = ChatHelpers.header( header[i] );
         }
         this.columns = header.length;
     }
@@ -134,117 +70,101 @@ public class TextTable
     {
         if( columns <= 0 ) return;
 
-        final int maxWidth = getMaxWidth( sender );
-
-        int[] minWidths = new int[ columns ];
-        int[] maxWidths = new int[ columns ];
-        int[] rowWidths = new int[ columns ];
+        int[] maxWidths = new int[columns];
 
         if( header != null )
         {
             for( int i = 0; i < columns; i++ )
             {
-                maxWidths[ i ] = minWidths[ i ] = getWidth( header[ i ], sender );
+                maxWidths[i] = getWidthFor( header[i], sender );
             }
         }
 
-        for( ITextComponent[] row : rows )
+        // Limit the number of rows to fit within a single chat window on default Minecraft
+        // options.
+        int height = isPlayer( sender ) ? 18 : 100;
+        int limit = rows.size() <= height ? rows.size() : height - 1;
+
+        for( int y = 0; y < limit; y++ )
         {
+            ITextComponent[] row = rows.get( y );
             for( int i = 0; i < row.length; i++ )
             {
-                int width = getWidth( row[ i ], sender );
-                rowWidths[ i ] += width;
-                if( width > maxWidths[ i ] )
-                {
-                    maxWidths[ i ] = width;
-                }
+                int width = getWidthFor( row[i], sender );
+                if( width > maxWidths[i] ) maxWidths[i] = width;
             }
         }
 
-        // Calculate the average width
-        for( int i = 0; i < columns; i++ )
-        {
-            rowWidths[ i ] = Math.max( rowWidths[ i ], rows.size() );
-        }
+        // Add a small amount of extra padding. This defaults to 3 spaces for players
+        // and 1 for everyone else.
+        int padding = isPlayer( sender ) ? getWidth( ' ' ) * 3 : 1;
+        for( int i = 0; i < maxWidths.length; i++ ) maxWidths[i] += padding;
 
-        int totalWidth = (columns - 1) * getWidth( SEPARATOR, sender );
+        int totalWidth = (columns - 1) * getWidthFor( SEPARATOR, sender );
         for( int x : maxWidths ) totalWidth += x;
 
         // TODO: Limit the widths of some entries if totalWidth > maxWidth
 
-        ITextComponent out = new TextComponentString( "" );
+        List<ITextComponent> out = new ArrayList<>();
 
         if( header != null )
         {
-            for( int i = 0; i < columns; i++ )
+            TextComponentString line = new TextComponentString( "" );
+            for( int i = 0; i < columns - 1; i++ )
             {
-                if( i != 0 ) out.appendSibling( SEPARATOR );
-                appendFixed( out, sender, header[ i ], maxWidths[ i ] );
+                appendFixedWidth( line, sender, header[i], maxWidths[i] );
+                line.appendSibling( SEPARATOR );
             }
-            out.appendSibling( LINE );
+            line.appendSibling( header[columns - 1] );
+            out.add( line );
 
             // Round the width up rather than down
-            int rowCharWidth = getWidth( '=', sender );
+            int rowCharWidth = getWidthFor( '=', sender );
             int rowWidth = totalWidth / rowCharWidth + (totalWidth % rowCharWidth == 0 ? 0 : 1);
-            out.appendSibling( coloured( StringUtils.repeat( '=', rowWidth ), TextFormatting.GRAY ) );
-            out.appendSibling( LINE );
+            out.add( coloured( StringUtils.repeat( '=', rowWidth ), TextFormatting.GRAY ) );
         }
 
-        for( int i = 0; i < rows.size(); i++ )
+        for( int i = 0; i < limit; i++ )
         {
+            TextComponentString line = new TextComponentString( "" );
             ITextComponent[] row = rows.get( i );
-            if( i != 0 ) out.appendSibling( LINE );
-            for( int j = 0; j < columns; j++ )
+            for( int j = 0; j < columns - 1; j++ )
             {
-                if( j != 0 ) out.appendSibling( SEPARATOR );
-                appendFixed( out, sender, row[ j ], maxWidths[ j ] );
+                appendFixedWidth( line, sender, row[j], maxWidths[j] );
+                line.appendSibling( SEPARATOR );
             }
+            line.appendSibling( row[columns - 1] );
+            out.add( line );
         }
 
-        sender.sendMessage( out );
-    }
-
-    private static void appendFixed( ITextComponent out, ICommandSender sender, ITextComponent entry, int maxWidth )
-    {
-        int length = getWidth( entry, sender );
-        int delta = length - maxWidth;
-        if( delta < 0 )
+        if( rows.size() > limit )
         {
-            // Convert to overflow;
-            delta = -delta;
+            out.add( coloured( (rows.size() - limit) + " additional rows...", TextFormatting.AQUA ) );
+        }
 
-            // We have to remove some padding as there is a padding added between formatted and unformatted text
-            if( !entry.getStyle().isEmpty() && isPlayer( sender ) ) delta -= 1;
+        if( isPlayer( sender ) && id != 0 )
+        {
+            ComputerCraftPacket packet = new ComputerCraftPacket();
+            packet.m_packetType = ComputerCraftPacket.PostChat;
+            packet.m_dataInt = new int[]{ id };
 
-            out.appendSibling( entry );
-
-            int spaceWidth = getWidth( ' ', sender );
-
-            int spaces = delta / spaceWidth;
-            int missing = delta % spaceWidth;
-            spaces -= missing;
-
-            ITextComponent component = new TextComponentString( StringUtils.repeat( ' ', spaces < 0 ? 0 : spaces ) );
-            if( missing > 0 )
+            String[] lines = packet.m_dataString = new String[out.size()];
+            for( int i = 0; i < out.size(); i++ )
             {
-                ITextComponent bold = new TextComponentString( StringUtils.repeat( ' ', missing ) );
-                bold.getStyle().setBold( true );
-                component.appendSibling( bold );
+                lines[i] = ITextComponent.Serializer.componentToJson( out.get( i ) );
             }
 
-            out.appendSibling( component );
-        }
-        else if( delta > 0 )
-        {
-            out.appendSibling( entry );
+            ComputerCraft.sendToPlayer( (EntityPlayerMP) sender, packet );
         }
         else
         {
-            out.appendSibling( entry );
-
-            // We have to add some padding as we expect a padding between formatted and unformatted text
-            // and there won't be.
-            if( entry.getStyle().isEmpty() && isPlayer( sender ) ) out.appendText( " " );
+            ITextComponent result = new TextComponentString( "" );
+            for( int i = 0; i < out.size(); i++ )
+            {
+                if( i > 0 ) result.appendSibling( LINE );
+                result.appendSibling( out.get( i ) );
+            }
+            sender.sendMessage( result );
         }
     }
 }

src/main/java/dan200/computercraft/shared/common/BlockGeneric.java

@@ -36,7 +36,7 @@ public abstract class BlockGeneric extends Block implements
     protected BlockGeneric( Material material )
     {
         super( material );
-        this.isBlockContainer = true;
+        this.hasTileEntity = true;
     }
 
     protected abstract IBlockState getDefaultBlockState( int damage, EnumFacing placedSide );

src/main/java/dan200/computercraft/shared/common/ClientTerminal.java

@@ -14,29 +14,28 @@ public class ClientTerminal implements ITerminal
     private boolean m_colour;
     private Terminal m_terminal;
     private boolean m_terminalChanged;
-    private boolean m_terminalChangedLastFrame;
 
     public ClientTerminal( boolean colour )
     {
         m_colour = colour;
         m_terminal = null;
         m_terminalChanged = false;
-        m_terminalChangedLastFrame = false;
     }
 
     public void update()
     {
-        m_terminalChangedLastFrame = m_terminalChanged || (m_terminal != null && m_terminal.getChanged());
         if( m_terminal != null )
         {
+            m_terminalChanged |= m_terminal.getChanged();
             m_terminal.clearChanged();
         }
-        m_terminalChanged = false;
     }
 
-    public boolean hasTerminalChanged()
+    public boolean pollTerminalChanged()
     {
-        return m_terminalChangedLastFrame;
+        boolean changed = m_terminalChanged;
+        m_terminalChanged = false;
+        return changed;
     }
 
     // ITerminal implementation

src/main/java/dan200/computercraft/shared/common/ColourableRecipe.java

@@ -86,7 +86,7 @@ public class ColourableRecipe extends IForgeRegistryEntry.Impl<IRecipe> implemen
     }
 
     @Override
-    public boolean isHidden()
+    public boolean isDynamic()
     {
         return true;
     }

src/main/java/dan200/computercraft/shared/common/ServerTerminal.java

@@ -54,6 +54,11 @@ public class ServerTerminal implements ITerminal
         }
     }
 
+    protected void markTerminalChanged()
+    {
+        m_terminalChanged = true;
+    }
+
     public void update()
     {
         m_terminalChangedLastFrame = m_terminalChanged || (m_terminal != null && m_terminal.getChanged());

src/main/java/dan200/computercraft/shared/computer/apis/CommandAPI.java

@@ -8,9 +8,7 @@ package dan200.computercraft.shared.computer.apis;
 
 import com.google.common.collect.ImmutableMap;
 import dan200.computercraft.ComputerCraft;
-import dan200.computercraft.api.lua.ILuaAPI;
-import dan200.computercraft.api.lua.ILuaContext;
-import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.*;
 import dan200.computercraft.shared.computer.blocks.TileCommandComputer;
 import dan200.computercraft.shared.util.WorldUtil;
 import net.minecraft.block.Block;
@@ -24,6 +22,7 @@ import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -82,7 +81,7 @@ public class CommandAPI implements ILuaAPI
                 sender.clearOutput();
 
                 int result = commandManager.executeCommand( sender, command );
-                return new Object[]{ (result > 0), sender.copyOutput() };
+                return new Object[] { (result > 0), sender.copyOutput() };
             }
             catch( Throwable t )
             {
@@ -90,7 +89,7 @@ public class CommandAPI implements ILuaAPI
                 {
                     ComputerCraft.log.error( "Error running command.", t );
                 }
-                return new Object[]{ false, createOutput( "Java Exception Thrown: " + t.toString() ) };
+                return new Object[] { false, createOutput( "Java Exception Thrown: " + t.toString() ) };
             }
         }
         else
@@ -131,7 +130,8 @@ public class CommandAPI implements ILuaAPI
     }
 
     @Override
-    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    @Nonnull
+    public MethodResult callMethod( @Nonnull ICallContext context, int method, @Nonnull Object[] arguments ) throws LuaException
     {
         switch( method )
         {
@@ -139,19 +139,19 @@ public class CommandAPI implements ILuaAPI
             {
                 // exec
                 final String command = getString( arguments, 0 );
-                return context.executeMainThreadTask( () -> doCommand( command ) );
+                return MethodResult.onMainThread( () -> MethodResult.of( doCommand( command ) ) );
             }
             case 1:
             {
                 // execAsync
                 final String command = getString( arguments, 0 );
                 long taskID = context.issueMainThreadTask( () -> doCommand( command ) );
-                return new Object[] { taskID };
+                return MethodResult.of( taskID );
             }
             case 2:
             {
                 // list
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     int i = 1;
                     Map<Object, Object> result = new HashMap<>();
@@ -182,7 +182,7 @@ public class CommandAPI implements ILuaAPI
                             }
                         }
                     }
-                    return new Object[]{ result };
+                    return MethodResult.of( result );
                 } );
             }
             case 3:
@@ -190,7 +190,7 @@ public class CommandAPI implements ILuaAPI
                 // getBlockPosition
                 // This is probably safe to do on the Lua thread. Probably.
                 BlockPos pos = m_computer.getPos();
-                return new Object[] { pos.getX(), pos.getY(), pos.getZ() };
+                return MethodResult.of( pos.getX(), pos.getY(), pos.getZ() );
             }
             case 4:
             {
@@ -201,7 +201,7 @@ public class CommandAPI implements ILuaAPI
                 final int maxx = getInt( arguments, 3 );
                 final int maxy = getInt( arguments, 4 );
                 final int maxz = getInt( arguments, 5 );
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     // Get the details of the block
                     World world = m_computer.getWorld();
@@ -236,7 +236,7 @@ public class CommandAPI implements ILuaAPI
                             }
                         }
                     }
-                    return new Object[]{ results };
+                    return MethodResult.of( results );
                 } );
             }
             case 5:
@@ -245,14 +245,14 @@ public class CommandAPI implements ILuaAPI
                 final int x = getInt( arguments, 0 );
                 final int y = getInt( arguments, 1 );
                 final int z = getInt( arguments, 2 );
-                return context.executeMainThreadTask( () ->
+                return MethodResult.onMainThread( () ->
                 {
                     // Get the details of the block
                     World world = m_computer.getWorld();
                     BlockPos position = new BlockPos( x, y, z );
                     if( WorldUtil.isBlockInWorld( world, position ) )
                     {
-                        return new Object[]{ getBlockInfo( world, position ) };
+                        return MethodResult.of( getBlockInfo( world, position ) );
                     }
                     else
                     {
@@ -262,8 +262,16 @@ public class CommandAPI implements ILuaAPI
             }
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
+
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( (ICallContext) context, method, arguments ).evaluate( context );
+    }
 }

src/main/java/dan200/computercraft/shared/computer/blocks/BlockCommandComputer.java

@@ -42,7 +42,7 @@ public class BlockCommandComputer extends BlockComputerBase
         super( Material.IRON );
         setBlockUnbreakable();
         setResistance( 6000000.0F );
-        setUnlocalizedName( "computercraft:command_computer" );
+        setTranslationKey( "computercraft:command_computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.FACING, EnumFacing.NORTH )
@@ -62,7 +62,7 @@ public class BlockCommandComputer extends BlockComputerBase
     @Deprecated
     public IBlockState getStateFromMeta( int meta )
     {
-        EnumFacing dir = EnumFacing.getFront( meta & 0x7 );
+        EnumFacing dir = EnumFacing.byIndex( meta & 0x7 );
         if( dir.getAxis() == EnumFacing.Axis.Y )
         {
             dir = EnumFacing.NORTH;

src/main/java/dan200/computercraft/shared/computer/blocks/BlockComputer.java

@@ -44,7 +44,7 @@ public class BlockComputer extends BlockComputerBase
     {
         super( Material.ROCK );
         setHardness( 2.0f );
-        setUnlocalizedName( "computercraft:computer" );
+        setTranslationKey( "computercraft:computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
         setDefaultState( this.blockState.getBaseState()
             .withProperty( Properties.FACING, EnumFacing.NORTH )
@@ -65,7 +65,7 @@ public class BlockComputer extends BlockComputerBase
     @Deprecated
     public IBlockState getStateFromMeta( int meta )
     {
-        EnumFacing dir = EnumFacing.getFront( meta & 0x7 );
+        EnumFacing dir = EnumFacing.byIndex( meta & 0x7 );
         if( dir.getAxis() == EnumFacing.Axis.Y )
         {
             dir = EnumFacing.NORTH;

src/main/java/dan200/computercraft/shared/computer/blocks/ComputerPeripheral.java

@@ -6,11 +6,15 @@
 
 package dan200.computercraft.shared.computer.blocks;
 
+import dan200.computercraft.api.lua.ICallContext;
 import dan200.computercraft.api.lua.ILuaContext;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.MethodResult;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 public class ComputerPeripheral
     implements IPeripheral
@@ -23,7 +27,7 @@ public class ComputerPeripheral
         m_type = type;
         m_computer = computer;
     }
-        
+
     // IPeripheral implementation
 
     @Nonnull
@@ -47,8 +51,9 @@ public class ComputerPeripheral
         };
     }
 
+    @Nonnull
     @Override
-    public Object[] callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments )
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ICallContext context, int method, @Nonnull Object[] arguments )
     {
         switch( method )
         {
@@ -56,45 +61,58 @@ public class ComputerPeripheral
             {
                 // turnOn
                 m_computer.turnOn();
-                return null;
+                return MethodResult.empty();
             }
             case 1:
             {
                 // shutdown
                 m_computer.shutdown();
-                return null;
+                return MethodResult.empty();
             }
             case 2:
             {
                 // reboot
                 m_computer.reboot();
-                return null;
+                return MethodResult.empty();
             }
             case 3:
             {
                 // getID
-                return new Object[] {
-                    m_computer.assignID()
-                };
+                return MethodResult.of( m_computer.assignID() );
             }
             case 4:
             {
                 // isOn
-                return new Object[] { m_computer.isOn() };
+                return MethodResult.of( m_computer.isOn() );
             }
             case 5:
                 // getLabel
-                return new Object[] { m_computer.getLabel() };
+                return MethodResult.of( m_computer.getLabel() );
             default:
             {
-                return null;
+                return MethodResult.empty();
             }
         }
     }
 
+    @Nullable
+    @Override
+    @Deprecated
+    public Object[] callMethod( @Nonnull IComputerAccess access, @Nonnull ILuaContext context, int method, @Nonnull Object[] arguments ) throws LuaException, InterruptedException
+    {
+        return callMethod( access, (ICallContext) context, method, arguments ).evaluate( context );
+    }
+
     @Override
     public boolean equals( IPeripheral other )
     {
         return (other != null && other.getClass() == this.getClass());
     }
+
+    @Nonnull
+    @Override
+    public Object getTarget()
+    {
+        return m_computer.getTile();
+    }
 }

src/main/java/dan200/computercraft/shared/computer/core/ServerComputer.java

@@ -94,6 +94,11 @@ public class ServerComputer extends ServerTerminal
         return m_computer.getAPIEnvironment();
     }
 
+    public Computer getComputer()
+    {
+        return m_computer;
+    }
+
     @Override
     public void update()
     {
@@ -149,7 +154,7 @@ public class ServerComputer extends ServerTerminal
         return packet;
     }
 
-    private ComputerCraftPacket createTerminalPacket() {
+    protected ComputerCraftPacket createTerminalPacket() {
         ComputerCraftPacket packet = new ComputerCraftPacket();
         packet.m_packetType = ComputerCraftPacket.ComputerTerminalChanged;
         packet.m_dataInt = new int[] { getInstanceID() };
@@ -460,7 +465,7 @@ public class ServerComputer extends ServerTerminal
         }
     }
 
-    private boolean isInteracting( EntityPlayer player )
+    protected boolean isInteracting( EntityPlayer player )
     {
         if( player == null ) return false;
 

src/main/java/dan200/computercraft/shared/computer/items/IComputerItem.java

@@ -16,4 +16,5 @@ public interface IComputerItem
     int getComputerID( @Nonnull ItemStack stack );
     String getLabel( @Nonnull ItemStack stack );
     ComputerFamily getFamily( @Nonnull ItemStack stack );
+    ItemStack withFamily(@Nonnull ItemStack stack, @Nonnull ComputerFamily family);
 }

src/main/java/dan200/computercraft/shared/computer/items/ItemCommandComputer.java

@@ -24,7 +24,7 @@ public class ItemCommandComputer extends ItemComputer
         super( block );
         setMaxStackSize( 64 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:command_computer" );
+        setTranslationKey( "computercraft:command_computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 

src/main/java/dan200/computercraft/shared/computer/items/ItemComputer.java

@@ -27,13 +27,13 @@ import javax.annotation.Nullable;
 public class ItemComputer extends ItemComputerBase
 {
     public static int HIGHEST_DAMAGE_VALUE_ID = 16382;
-    
+
     public ItemComputer( Block block )
     {
         super( block );
         setMaxStackSize( 64 );
         setHasSubtypes( true );
-        setUnlocalizedName( "computercraft:computer" );
+        setTranslationKey( "computercraft:computer" );
         setCreativeTab( ComputerCraft.mainCreativeTab );
     }
 
@@ -87,7 +87,7 @@ public class ItemComputer extends ItemComputerBase
             TileEntity tile = world.getTileEntity( pos );
             if( tile != null && tile instanceof IComputerTile )
             {
-                IComputerTile computer = (IComputerTile)tile;
+                IComputerTile computer = (IComputerTile) tile;
                 setupComputerAfterPlacement( stack, computer );
             }
             return true;
@@ -114,7 +114,7 @@ public class ItemComputer extends ItemComputerBase
 
     @Nonnull
     @Override
-    public String getUnlocalizedName( @Nonnull ItemStack stack )
+    public String getTranslationKey( @Nonnull ItemStack stack )
     {
         switch( getFamily( stack ) )
         {
@@ -146,10 +146,16 @@ public class ItemComputer extends ItemComputerBase
         else
         {
             int damage = stack.getItemDamage() & 0x3fff;
-            return ( damage - 1 );
+            return (damage - 1);
         }
     }
 
+    @Override
+    public ItemStack withFamily( @Nonnull ItemStack stack, @Nonnull ComputerFamily family )
+    {
+        return ComputerItemFactory.create( getComputerID( stack ), getLabel( stack ), family );
+    }
+
     @Override
     public ComputerFamily getFamily( int damage )
     {

src/main/java/dan200/computercraft/shared/computer/recipe/ComputerConvertRecipe.java

@@ -0,0 +1,66 @@
+package dan200.computercraft.shared.computer.recipe;
+
+import dan200.computercraft.shared.computer.items.IComputerItem;
+import net.minecraft.inventory.InventoryCrafting;
+import net.minecraft.item.ItemStack;
+import net.minecraft.item.crafting.Ingredient;
+import net.minecraft.item.crafting.ShapedRecipes;
+import net.minecraft.world.World;
+import net.minecraftforge.common.crafting.CraftingHelper;
+
+import javax.annotation.Nonnull;
+
+/**
+ * Represents a recipe which converts a computer from one form into another.
+ */
+public abstract class ComputerConvertRecipe extends ShapedRecipes
+{
+    public ComputerConvertRecipe( String group, @Nonnull CraftingHelper.ShapedPrimer primer, @Nonnull ItemStack result )
+    {
+        super( group, primer.width, primer.height, primer.input, result );
+    }
+
+    @Nonnull
+    protected abstract ItemStack convert( @Nonnull ItemStack stack );
+
+    @Override
+    public boolean matches( @Nonnull InventoryCrafting inventory, @Nonnull World world )
+    {
+        // See if we match the recipe, and extract the input computercraft ID
+        ItemStack computerStack = null;
+        for( int y = 0; y < 3; ++y )
+        {
+            for( int x = 0; x < 3; ++x )
+            {
+                ItemStack stack = inventory.getStackInRowAndColumn( x, y );
+                Ingredient target = getIngredients().get( x + y * 3 );
+
+                // First verify we match the ingredient
+                if( !target.apply( stack ) ) return false;
+
+                // We want to ensure we have a computer item somewhere in the recipe
+                if( stack.getItem() instanceof IComputerItem ) computerStack = stack;
+            }
+        }
+
+        return computerStack != null;
+    }
+
+    @Nonnull
+    @Override
+    public ItemStack getCraftingResult( @Nonnull InventoryCrafting inventory )
+    {
+        for( int y = 0; y < 3; ++y )
+        {
+            for( int x = 0; x < 3; ++x )
+            {
+                ItemStack item = inventory.getStackInRowAndColumn( x, y );
+
+                // If we're a computer, convert!
+                if( item.getItem() instanceof IComputerItem ) return convert( item );
+            }
+        }
+
+        return ItemStack.EMPTY;
+    }
+}

src/main/java/dan200/computercraft/shared/computer/recipe/ComputerFamilyRecipe.java

@@ -0,0 +1,47 @@
+package dan200.computercraft.shared.computer.recipe;
+
+import com.google.gson.JsonObject;
+import dan200.computercraft.shared.computer.core.ComputerFamily;
+import dan200.computercraft.shared.computer.items.IComputerItem;
+import dan200.computercraft.shared.util.RecipeUtil;
+import net.minecraft.item.ItemStack;
+import net.minecraft.item.crafting.IRecipe;
+import net.minecraft.util.JsonUtils;
+import net.minecraftforge.common.crafting.CraftingHelper;
+import net.minecraftforge.common.crafting.IRecipeFactory;
+import net.minecraftforge.common.crafting.JsonContext;
+
+import javax.annotation.Nonnull;
+
+public class ComputerFamilyRecipe extends ComputerConvertRecipe
+{
+    private final ComputerFamily family;
+
+    public ComputerFamilyRecipe( String group, @Nonnull CraftingHelper.ShapedPrimer primer, @Nonnull ItemStack result, ComputerFamily family )
+    {
+        super( group, primer, result );
+        this.family = family;
+    }
+
+    @Nonnull
+    @Override
+    protected ItemStack convert( @Nonnull ItemStack stack )
+    {
+        return ((IComputerItem) stack.getItem()).withFamily( stack, family );
+    }
+
+    public static class Factory implements IRecipeFactory
+    {
+        @Override
+        public IRecipe parse( JsonContext context, JsonObject json )
+        {
+            String group = JsonUtils.getString( json, "group", "" );
+            ComputerFamily family = RecipeUtil.getFamily( json, "family" );
+
+            CraftingHelper.ShapedPrimer primer = RecipeUtil.getPrimer( context, json );
+            ItemStack result = deserializeItem( JsonUtils.getJsonObject( json, "result" ), false );
+
+            return new ComputerFamilyRecipe( group, primer, result, family );
+        }
+    }
+}

src/main/java/dan200/computercraft/shared/computer/recipe/ComputerIngredient.java

@@ -0,0 +1,66 @@
+package dan200.computercraft.shared.computer.recipe;
+
+import com.google.gson.JsonObject;
+import com.google.gson.JsonSyntaxException;
+import dan200.computercraft.shared.computer.core.ComputerFamily;
+import dan200.computercraft.shared.computer.items.IComputerItem;
+import dan200.computercraft.shared.util.RecipeUtil;
+import net.minecraft.item.Item;
+import net.minecraft.item.ItemStack;
+import net.minecraft.item.crafting.Ingredient;
+import net.minecraft.util.JsonUtils;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.crafting.IIngredientFactory;
+import net.minecraftforge.common.crafting.JsonContext;
+import net.minecraftforge.fml.common.registry.ForgeRegistries;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+/**
+ * Represents an ingredient which requires an item to have a specific
+ * computer family. This allows us to have operations which only work 
+ * on normal or 
+ */
+public class ComputerIngredient extends Ingredient
+{
+    private final IComputerItem item;
+    private final ComputerFamily family;
+
+    public <T extends Item & IComputerItem> ComputerIngredient( T item, int data, ComputerFamily family )
+    {
+        super( new ItemStack( item, 1, data ) );
+
+        this.item = item;
+        this.family = family;
+    }
+
+    @Override
+    public boolean apply( @Nullable ItemStack stack )
+    {
+        return stack != null && stack.getItem() == item && item.getFamily( stack ) == family;
+    }
+
+    public static class Factory implements IIngredientFactory
+    {
+        @Nonnull
+        @Override
+        public Ingredient parse( JsonContext context, JsonObject json )
+        {
+            String itemName = context.appendModId( JsonUtils.getString( json, "item" ) );
+            int data = JsonUtils.getInt( json, "data", 0 );
+            ComputerFamily family = RecipeUtil.getFamily( json, "family" );
+
+            Item item = ForgeRegistries.ITEMS.getValue( new ResourceLocation( itemName ) );
+
+            if( item == null ) throw new JsonSyntaxException( "Unknown item '" + itemName + "'" );
+            if( !(item instanceof IComputerItem) )
+            {
+                throw new JsonSyntaxException( "Item '" + itemName + "' is not a computer item" );
+            }
+
+
+            return new ComputerIngredient( (Item & IComputerItem) item, data, family );
+        }
+    }
+}

src/main/java/dan200/computercraft/shared/integration/charset/BundledCapabilityProvider.java

@@ -0,0 +1,88 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2018. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.integration.charset;
+
+import dan200.computercraft.shared.common.TileGeneric;
+import net.minecraft.util.EnumFacing;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.capabilities.ICapabilityProvider;
+import pl.asie.charset.api.wires.IBundledEmitter;
+import pl.asie.charset.api.wires.IBundledReceiver;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import static dan200.computercraft.shared.integration.charset.IntegrationCharset.CAPABILITY_EMITTER;
+import static dan200.computercraft.shared.integration.charset.IntegrationCharset.CAPABILITY_RECEIVER;
+
+final class BundledCapabilityProvider implements ICapabilityProvider
+{
+    private final TileGeneric tile;
+    private IBundledReceiver receiver;
+    private IBundledEmitter[] emitters;
+
+    BundledCapabilityProvider( TileGeneric tile )
+    {
+        this.tile = tile;
+    }
+
+    @Override
+    public boolean hasCapability( @Nonnull Capability<?> capability, @Nullable EnumFacing side )
+    {
+        return capability == CAPABILITY_EMITTER || capability == CAPABILITY_RECEIVER;
+    }
+
+    @Nullable
+    @Override
+    public <T> T getCapability( @Nonnull Capability<T> capability, @Nullable EnumFacing side )
+    {
+        if( capability == CAPABILITY_RECEIVER )
+        {
+            IBundledReceiver receiver = this.receiver;
+            if( receiver == null ) receiver = this.receiver = tile::onNeighbourChange;
+
+            return CAPABILITY_RECEIVER.cast( receiver );
+        }
+        else if( capability == CAPABILITY_EMITTER )
+        {
+            IBundledEmitter[] emitters = this.emitters;
+            if( emitters == null ) emitters = this.emitters = new IBundledEmitter[7];
+
+            int index = side == null ? 6 : side.getIndex();
+            IBundledEmitter emitter = emitters[index];
+            if( emitter == null )
+            {
+                if( side == null )
+                {
+                    emitter = emitters[index] = () -> {
+                        int flags = 0;
+                        for( EnumFacing facing : EnumFacing.VALUES ) flags |= tile.getBundledRedstoneOutput( facing );
+                        return toBytes( flags );
+                    };
+                }
+                else
+                {
+                    emitter = emitters[index] = () -> toBytes( tile.getBundledRedstoneOutput( side ) );
+                }
+            }
+            ;
+
+            return CAPABILITY_EMITTER.cast( emitter );
+        }
+        else
+        {
+            return null;
+        }
+    }
+
+    private static byte[] toBytes( int flag )
+    {
+        byte[] channels = new byte[16];
+        for( int i = 0; i < 16; i++ ) channels[i] = (flag & (1 << i)) == 0 ? (byte) 0 : 15;
+        return channels;
+    }
+}