Expose peripherals as a capability

This registers IPeripheral as a capability. As a result, all (Minecraft
facing) functionality operates using LazyOptional<_>s instead.

Peripheral providers should now return a LazyOptional<IPeripheral> too.
Hopefully this will allow custom peripherals to mark themselves as
invalid (say, because a dependency has changed).

While peripheral providers are somewhat redundant, they still have their
usages. If a peripheral is applied to a large number of blocks (for
instance, all inventories) then using capabilities does incur some
memory overhead.

We also make the following changes based on the above:
 - Remove the default implementation for IWiredElement, migrating the
   definition to a common "Capabilities" class.

 - Remove IPeripheralTile - we'll exclusively use capabilities now.
   Absurdly this is the most complex change, as all TEs needed to be
   migrated too.

   I'm not 100% sure of the correctness of this changes so far - I've
   tested it pretty well, but blocks with more complex peripheral logic
   (wired/wireless modems and turtles) are still a little messy.

 - Remove the "command block" peripheral provider, attaching a
   capability instead.

config/checkstyle/checkstyle.xml

@@ -114,11 +114,11 @@
         </module>
         <module name="ParameterName" />
         <module name="StaticVariableName">
-            <property name="format" value="^[a-z][a-zA-Z0-9]*|CAPABILITY(_[A-Z]+)?$" />
+            <property name="format" value="^[a-z][a-zA-Z0-9]*|CAPABILITY(_[A-Z_]+)?$" />
             <property name="applyToPrivate" value="false" />
         </module>
         <module name="StaticVariableName">
-            <property name="format" value="^(s_)?[a-z][a-zA-Z0-9]*|CAPABILITY(_[A-Z]+)?$" />
+            <property name="format" value="^(s_)?[a-z][a-zA-Z0-9]*|CAPABILITY(_[A-Z_]+)?$" />
             <property name="applyToPrivate" value="true" />
         </module>
         <module name="TypeName" />

src/main/java/dan200/computercraft/ComputerCraftAPIImpl.java

@@ -24,7 +24,6 @@ import dan200.computercraft.core.filesystem.ResourceMount;
 import dan200.computercraft.shared.*;
 import dan200.computercraft.shared.peripheral.modem.wireless.WirelessNetwork;
 import dan200.computercraft.shared.util.IDAssigner;
-import dan200.computercraft.shared.wired.CapabilityWiredElement;
 import dan200.computercraft.shared.wired.WiredNode;
 import net.minecraft.resources.IReloadableResourceManager;
 import net.minecraft.tileentity.TileEntity;
@@ -41,6 +40,8 @@ import java.io.File;
 import java.lang.ref.WeakReference;
 import java.util.Map;
 
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_WIRED_ELEMENT;
+
 public final class ComputerCraftAPIImpl implements IComputerCraftAPI
 {
     public static final ComputerCraftAPIImpl INSTANCE = new ComputerCraftAPIImpl();
@@ -147,6 +148,6 @@ public final class ComputerCraftAPIImpl implements IComputerCraftAPI
     public LazyOptional<IWiredElement> getWiredElementAt( @Nonnull IBlockReader world, @Nonnull BlockPos pos, @Nonnull Direction side )
     {
         TileEntity tile = world.getTileEntity( pos );
-        return tile == null ? LazyOptional.empty() : tile.getCapability( CapabilityWiredElement.CAPABILITY, side );
+        return tile == null ? LazyOptional.empty() : tile.getCapability( CAPABILITY_WIRED_ELEMENT, side );
     }
 }

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

@@ -6,13 +6,17 @@
 package dan200.computercraft.api.peripheral;
 
 import dan200.computercraft.api.lua.LuaFunction;
+import net.minecraftforge.common.capabilities.Capability;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
 /**
- * The interface that defines a peripheral. See {@link IPeripheralProvider} for how to associate blocks with
+ * The interface that defines a peripheral.
- * peripherals.
+ *
+ * In order to expose a peripheral for your block or tile entity, you may either attach a {@link Capability}, or
+ * register a {@link IPeripheralProvider}. It is <em>not</em> recommended to implement {@link IPeripheral} directly on
+ * the tile.
  *
  * Peripherals should provide a series of methods to the user, either using {@link LuaFunction} or by implementing
  * {@link IDynamicPeripheral}.

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

@@ -9,14 +9,15 @@ import net.minecraft.tileentity.TileEntity;
 import net.minecraft.util.Direction;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
+import net.minecraftforge.common.util.LazyOptional;
 
 import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
 
 /**
  * This interface is used to create peripheral implementations for blocks.
  *
- * If you have a {@link TileEntity} which acts as a peripheral, you may alternatively implement {@link IPeripheralTile}.
+ * If you have a {@link TileEntity} which acts as a peripheral, you may alternatively expose the {@link IPeripheral}
+ * capability.
  *
  * @see dan200.computercraft.api.ComputerCraftAPI#registerPeripheralProvider(IPeripheralProvider)
  */
@@ -29,9 +30,9 @@ public interface IPeripheralProvider
      * @param world The world the block is in.
      * @param pos   The position the block is at.
      * @param side  The side to get the peripheral from.
-     * @return A peripheral, or {@code null} if there is not a peripheral here you'd like to handle.
+     * @return A peripheral, or {@link LazyOptional#empty()} if there is not a peripheral here you'd like to handle.
      * @see dan200.computercraft.api.ComputerCraftAPI#registerPeripheralProvider(IPeripheralProvider)
      */
-    @Nullable
+    @Nonnull
-    IPeripheral getPeripheral( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull Direction side );
+    LazyOptional<IPeripheral> getPeripheral( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull Direction side );
 }

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

@@ -1,32 +0,0 @@
-/*
- * This file is part of the public ComputerCraft API - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2020. 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 net.minecraft.util.Direction;
-import net.minecraft.util.math.BlockPos;
-import net.minecraft.world.World;
-
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-
-/**
- * A {@link net.minecraft.tileentity.TileEntity} which may act as a peripheral.
- *
- * If you need more complex capabilities (such as handling TEs not belonging to your mod), you should use
- * {@link IPeripheralProvider}.
- */
-public interface IPeripheralTile
-{
-    /**
-     * Get the peripheral on the given {@code side}.
-     *
-     * @param side The side to get the peripheral from.
-     * @return A peripheral, or {@code null} if there is not a peripheral here.
-     * @see IPeripheralProvider#getPeripheral(World, BlockPos, Direction)
-     */
-    @Nullable
-    IPeripheral getPeripheral( @Nonnull Direction side );
-}

src/main/java/dan200/computercraft/shared/Capabilities.java

@@ -0,0 +1,25 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared;
+
+import dan200.computercraft.api.network.wired.IWiredElement;
+import dan200.computercraft.api.peripheral.IPeripheral;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.capabilities.CapabilityInject;
+
+public final class Capabilities
+{
+    @CapabilityInject( IPeripheral.class )
+    public static Capability<IPeripheral> CAPABILITY_PERIPHERAL = null;
+
+    @CapabilityInject( IWiredElement.class )
+    public static Capability<IWiredElement> CAPABILITY_WIRED_ELEMENT = null;
+
+    private Capabilities()
+    {
+    }
+}

src/main/java/dan200/computercraft/shared/Peripherals.java

@@ -8,15 +8,22 @@ package dan200.computercraft.shared;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.IPeripheralProvider;
+import dan200.computercraft.shared.util.CapabilityUtil;
+import net.minecraft.tileentity.TileEntity;
 import net.minecraft.util.Direction;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
+import net.minecraftforge.common.util.LazyOptional;
+import net.minecraftforge.common.util.NonNullConsumer;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.Collection;
 import java.util.LinkedHashSet;
 import java.util.Objects;
 
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+
 public final class Peripherals
 {
     private static final Collection<IPeripheralProvider> providers = new LinkedHashSet<>();
@@ -29,20 +36,29 @@ public final class Peripherals
         providers.add( provider );
     }
 
-    public static IPeripheral getPeripheral( World world, BlockPos pos, Direction side )
+    @Nullable
+    public static IPeripheral getPeripheral( World world, BlockPos pos, Direction side, NonNullConsumer<LazyOptional<IPeripheral>> invalidate )
     {
-        return World.isValid( pos ) && !world.isRemote ? getPeripheralAt( world, pos, side ) : null;
+        return World.isValid( pos ) && !world.isRemote ? getPeripheralAt( world, pos, side, invalidate ) : null;
     }
 
-    private static IPeripheral getPeripheralAt( World world, BlockPos pos, Direction side )
+    @Nullable
+    private static IPeripheral getPeripheralAt( World world, BlockPos pos, Direction side, NonNullConsumer<LazyOptional<IPeripheral>> invalidate )
     {
+        TileEntity block = world.getTileEntity( pos );
+        if( block != null )
+        {
+            LazyOptional<IPeripheral> peripheral = block.getCapability( CAPABILITY_PERIPHERAL, side );
+            if( peripheral.isPresent() ) return CapabilityUtil.unwrap( peripheral, invalidate );
+        }
+
         // Try the handlers in order:
         for( IPeripheralProvider peripheralProvider : providers )
         {
             try
             {
-                IPeripheral peripheral = peripheralProvider.getPeripheral( world, pos, side );
+                LazyOptional<IPeripheral> peripheral = peripheralProvider.getPeripheral( world, pos, side );
-                if( peripheral != null ) return peripheral;
+                if( peripheral.isPresent() ) return CapabilityUtil.unwrap( peripheral, invalidate );
             }
             catch( Exception e )
             {

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

@@ -50,7 +50,7 @@ public abstract class BlockGeneric extends Block
     @Nonnull
     @Override
     @Deprecated
-    public final ActionResultType onBlockActivated( BlockState state, World world, BlockPos pos, PlayerEntity player, Hand hand, BlockRayTraceResult hit )
+    public final ActionResultType onBlockActivated( @Nonnull BlockState state, World world, @Nonnull BlockPos pos, @Nonnull PlayerEntity player, @Nonnull Hand hand, @Nonnull BlockRayTraceResult hit )
     {
         TileEntity tile = world.getTileEntity( pos );
         return tile instanceof TileGeneric ? ((TileGeneric) tile).onActivate( player, hand, hit ) : ActionResultType.PASS;
@@ -58,7 +58,7 @@ public abstract class BlockGeneric extends Block
 
     @Override
     @Deprecated
-    public final void neighborChanged( BlockState state, World world, BlockPos pos, Block neighbourBlock, BlockPos neighbourPos, boolean isMoving )
+    public final void neighborChanged( @Nonnull BlockState state, World world, @Nonnull BlockPos pos, @Nonnull Block neighbourBlock, @Nonnull BlockPos neighbourPos, boolean isMoving )
     {
         TileEntity tile = world.getTileEntity( pos );
         if( tile instanceof TileGeneric ) ((TileGeneric) tile).onNeighbourChange( neighbourPos );
@@ -73,7 +73,7 @@ public abstract class BlockGeneric extends Block
 
     @Override
     @Deprecated
-    public void tick( BlockState state, ServerWorld world, BlockPos pos, Random rand )
+    public void tick( @Nonnull BlockState state, ServerWorld world, @Nonnull BlockPos pos, @Nonnull Random rand )
     {
         TileEntity te = world.getTileEntity( pos );
         if( te instanceof TileGeneric ) ((TileGeneric) te).blockTick();

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

@@ -67,7 +67,7 @@ public class ComputerPeripheral implements IPeripheral
     @Override
     public boolean equals( IPeripheral other )
     {
-        return other != null && other.getClass() == getClass();
+        return other instanceof ComputerPeripheral && computer == ((ComputerPeripheral) other).computer;
     }
 
     @Nonnull

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

@@ -8,12 +8,24 @@ package dan200.computercraft.shared.computer.blocks;
 import dan200.computercraft.shared.computer.core.IComputer;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 
+import java.util.function.Supplier;
+
 /**
  * A proxy object for computer objects, delegating to {@link IComputer} or {@link TileComputer} where appropriate.
  */
-public abstract class ComputerProxy
+public final class ComputerProxy
 {
-    protected abstract TileComputerBase getTile();
+    private final Supplier<TileComputerBase> get;
+
+    public ComputerProxy( Supplier<TileComputerBase> get )
+    {
+        this.get = get;
+    }
+
+    protected TileComputerBase getTile()
+    {
+        return get.get();
+    }
 
     public void turnOn()
     {

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

@@ -6,11 +6,13 @@
 package dan200.computercraft.shared.computer.blocks;
 
 import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.computer.ComputerSide;
 import dan200.computercraft.shared.computer.core.ComputerFamily;
 import dan200.computercraft.shared.computer.core.ComputerState;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.computer.inventory.ContainerComputer;
+import dan200.computercraft.shared.util.CapabilityUtil;
 import dan200.computercraft.shared.util.NamedTileEntityType;
 import net.minecraft.block.BlockState;
 import net.minecraft.entity.player.PlayerEntity;
@@ -19,10 +21,14 @@ import net.minecraft.inventory.container.Container;
 import net.minecraft.tileentity.TileEntityType;
 import net.minecraft.util.Direction;
 import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.util.LazyOptional;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+
 public class TileComputer extends TileComputerBase
 {
     public static final NamedTileEntityType<TileComputer> FACTORY_NORMAL = NamedTileEntityType.create(
@@ -35,7 +41,8 @@ public class TileComputer extends TileComputerBase
         f -> new TileComputer( ComputerFamily.ADVANCED, f )
     );
 
-    private ComputerProxy m_proxy;
+    private ComputerProxy proxy;
+    private LazyOptional<IPeripheral> peripheral;
 
     public TileComputer( ComputerFamily family, TileEntityType<? extends TileComputer> type )
     {
@@ -55,23 +62,6 @@ public class TileComputer extends TileComputerBase
         return computer;
     }
 
-    @Override
-    public ComputerProxy createProxy()
-    {
-        if( m_proxy == null )
-        {
-            m_proxy = new ComputerProxy()
-            {
-                @Override
-                protected TileComputerBase getTile()
-                {
-                    return TileComputer.this;
-                }
-            };
-        }
-        return m_proxy;
-    }
-
     public boolean isUsableByPlayer( PlayerEntity player )
     {
         return isUsable( player, false );
@@ -109,4 +99,30 @@ public class TileComputer extends TileComputerBase
     {
         return new ContainerComputer( id, this );
     }
+
+    @Nonnull
+    @Override
+    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> cap, @Nullable Direction side )
+    {
+        if( cap == CAPABILITY_PERIPHERAL )
+        {
+            if( peripheral == null )
+            {
+                peripheral = LazyOptional.of( () -> {
+                    if( proxy == null ) proxy = new ComputerProxy( () -> this );
+                    return new ComputerPeripheral( "computer", proxy );
+                } );
+            }
+            return peripheral.cast();
+        }
+
+        return super.getCapability( cap, side );
+    }
+
+    @Override
+    protected void invalidateCaps()
+    {
+        super.invalidateCaps();
+        peripheral = CapabilityUtil.invalidate( peripheral );
+    }
 }

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

@@ -7,7 +7,6 @@ package dan200.computercraft.shared.computer.blocks;
 
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IPeripheral;
-import dan200.computercraft.api.peripheral.IPeripheralTile;
 import dan200.computercraft.core.computer.ComputerSide;
 import dan200.computercraft.shared.BundledRedstone;
 import dan200.computercraft.shared.Peripherals;
@@ -45,7 +44,7 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.util.Objects;
 
-public abstract class TileComputerBase extends TileGeneric implements IComputerTile, ITickableTileEntity, IPeripheralTile, INameable, INamedContainerProvider
+public abstract class TileComputerBase extends TileGeneric implements IComputerTile, ITickableTileEntity, INameable, INamedContainerProvider
 {
     private static final String NBT_ID = "ComputerId";
     private static final String NBT_LABEL = "Label";
@@ -226,7 +225,8 @@ public abstract class TileComputerBase extends TileGeneric implements IComputerT
         computer.setBundledRedstoneInput( localDir, BundledRedstone.getOutput( getWorld(), offset, offsetSide ) );
         if( !isPeripheralBlockedOnSide( localDir ) )
         {
-            computer.setPeripheral( localDir, Peripherals.getPeripheral( getWorld(), offset, offsetSide ) );
+            IPeripheral peripheral = Peripherals.getPeripheral( getWorld(), offset, offsetSide, o -> updateInput( dir ) );
+            computer.setPeripheral( localDir, peripheral );
         }
     }
 
@@ -272,7 +272,6 @@ public abstract class TileComputerBase extends TileGeneric implements IComputerT
         ServerComputer computer = getServerComputer();
         if( computer == null ) return;
 
-        BlockPos pos = computer.getPosition();
         for( Direction dir : DirectionUtil.FACINGS )
         {
             BlockPos offset = pos.offset( dir );
@@ -287,6 +286,16 @@ public abstract class TileComputerBase extends TileGeneric implements IComputerT
         updateInput();
     }
 
+    private void updateInput( Direction dir )
+    {
+        if( getWorld() == null || getWorld().isRemote ) return;
+
+        ServerComputer computer = getServerComputer();
+        if( computer == null ) return;
+
+        updateSideInput( computer, dir, pos.offset( dir ) );
+    }
+
     public void updateOutput()
     {
         // Update redstone
@@ -299,8 +308,6 @@ public abstract class TileComputerBase extends TileGeneric implements IComputerT
 
     protected abstract ServerComputer createComputer( int instanceID, int id );
 
-    public abstract ComputerProxy createProxy();
-
     @Override
     public final int getComputerID()
     {
@@ -404,13 +411,6 @@ public abstract class TileComputerBase extends TileGeneric implements IComputerT
         copy.m_instanceID = -1;
     }
 
-    @Nullable
-    @Override
-    public IPeripheral getPeripheral( @Nonnull Direction side )
-    {
-        return new ComputerPeripheral( "computer", createProxy() );
-    }
-
     @Nonnull
     @Override
     public ITextComponent getName()

src/main/java/dan200/computercraft/shared/peripheral/commandblock/CommandBlockPeripheral.java

@@ -5,15 +5,33 @@
  */
 package dan200.computercraft.shared.peripheral.commandblock;
 
+import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.lua.LuaFunction;
 import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.shared.util.CapabilityUtil;
 import net.minecraft.tileentity.CommandBlockTileEntity;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.Direction;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.capabilities.ICapabilityProvider;
+import net.minecraftforge.common.util.LazyOptional;
+import net.minecraftforge.event.AttachCapabilitiesEvent;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+import net.minecraftforge.fml.common.Mod;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
-public class CommandBlockPeripheral implements IPeripheral
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+
+@Mod.EventBusSubscriber
+public class CommandBlockPeripheral implements IPeripheral, ICapabilityProvider
 {
+    private static final ResourceLocation CAP_ID = new ResourceLocation( ComputerCraft.MOD_ID, "command_block" );
+
     private final CommandBlockTileEntity commandBlock;
+    private LazyOptional<IPeripheral> self;
 
     public CommandBlockPeripheral( CommandBlockTileEntity commandBlock )
     {
@@ -53,4 +71,33 @@ public class CommandBlockPeripheral implements IPeripheral
     {
         return other != null && other.getClass() == getClass();
     }
+
+    @Nonnull
+    @Override
+    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> cap, @Nullable Direction side )
+    {
+        if( cap == CAPABILITY_PERIPHERAL )
+        {
+            if( self == null ) self = LazyOptional.of( () -> this );
+            return self.cast();
+        }
+        return LazyOptional.empty();
+    }
+
+    private void invalidate()
+    {
+        self = CapabilityUtil.invalidate( self );
+    }
+
+    @SubscribeEvent
+    public static void onCapability( AttachCapabilitiesEvent<TileEntity> event )
+    {
+        TileEntity tile = event.getObject();
+        if( tile instanceof CommandBlockTileEntity )
+        {
+            CommandBlockPeripheral peripheral = new CommandBlockPeripheral( (CommandBlockTileEntity) tile );
+            event.addCapability( CAP_ID, peripheral );
+            event.addListener( peripheral::invalidate );
+        }
+    }
 }

src/main/java/dan200/computercraft/shared/peripheral/diskdrive/TileDiskDrive.java

@@ -11,13 +11,9 @@ import dan200.computercraft.api.filesystem.IWritableMount;
 import dan200.computercraft.api.media.IMedia;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
-import dan200.computercraft.api.peripheral.IPeripheralTile;
 import dan200.computercraft.shared.MediaProviders;
 import dan200.computercraft.shared.common.TileGeneric;
-import dan200.computercraft.shared.util.DefaultInventory;
+import dan200.computercraft.shared.util.*;
-import dan200.computercraft.shared.util.InventoryUtil;
-import dan200.computercraft.shared.util.NamedTileEntityType;
-import dan200.computercraft.shared.util.RecordUtil;
 import net.minecraft.block.BlockState;
 import net.minecraft.entity.item.ItemEntity;
 import net.minecraft.entity.player.PlayerEntity;
@@ -45,9 +41,10 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
 
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
 import static net.minecraftforge.items.CapabilityItemHandler.ITEM_HANDLER_CAPABILITY;
 
-public final class TileDiskDrive extends TileGeneric implements DefaultInventory, ITickableTileEntity, IPeripheralTile, INameable, INamedContainerProvider
+public final class TileDiskDrive extends TileGeneric implements DefaultInventory, ITickableTileEntity, INameable, INamedContainerProvider
 {
     private static final String NBT_NAME = "CustomName";
     private static final String NBT_ITEM = "Item";
@@ -69,6 +66,7 @@ public final class TileDiskDrive extends TileGeneric implements DefaultInventory
     @Nonnull
     private ItemStack m_diskStack = ItemStack.EMPTY;
     private LazyOptional<IItemHandlerModifiable> itemHandlerCap;
+    private LazyOptional<IPeripheral> peripheralCap;
     private IMount m_diskMount = null;
 
     private boolean m_recordQueued = false;
@@ -92,11 +90,8 @@ public final class TileDiskDrive extends TileGeneric implements DefaultInventory
     protected void invalidateCaps()
     {
         super.invalidateCaps();
-        if( itemHandlerCap != null )
+        itemHandlerCap = CapabilityUtil.invalidate( itemHandlerCap );
-        {
+        peripheralCap = CapabilityUtil.invalidate( peripheralCap );
-            itemHandlerCap.invalidate();
-            itemHandlerCap = null;
-        }
     }
 
     @Nonnull
@@ -313,12 +308,6 @@ public final class TileDiskDrive extends TileGeneric implements DefaultInventory
         setInventorySlotContents( 0, ItemStack.EMPTY );
     }
 
-    @Override
-    public IPeripheral getPeripheral( @Nonnull Direction side )
-    {
-        return new DiskDrivePeripheral( this );
-    }
-
     @Nonnull
     ItemStack getDiskStack()
     {
@@ -535,6 +524,13 @@ public final class TileDiskDrive extends TileGeneric implements DefaultInventory
             if( itemHandlerCap == null ) itemHandlerCap = LazyOptional.of( () -> new InvWrapper( this ) );
             return itemHandlerCap.cast();
         }
+
+        if( cap == CAPABILITY_PERIPHERAL )
+        {
+            if( peripheralCap == null ) peripheralCap = LazyOptional.of( () -> new DiskDrivePeripheral( this ) );
+            return peripheralCap.cast();
+        }
+
         return super.getCapability( cap, side );
     }
 

src/main/java/dan200/computercraft/shared/peripheral/modem/wired/CableModemVariant.java

@@ -9,6 +9,7 @@ import net.minecraft.util.Direction;
 import net.minecraft.util.IStringSerializable;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 
 public enum CableModemVariant implements IStringSerializable
 {
@@ -69,6 +70,7 @@ public enum CableModemVariant implements IStringSerializable
         return name;
     }
 
+    @Nullable
     public Direction getFacing()
     {
         return facing;

src/main/java/dan200/computercraft/shared/peripheral/modem/wired/TileCable.java

@@ -11,14 +11,13 @@ import dan200.computercraft.api.ComputerCraftAPI;
 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.IPeripheralTile;
 import dan200.computercraft.shared.command.CommandCopy;
 import dan200.computercraft.shared.common.TileGeneric;
 import dan200.computercraft.shared.peripheral.modem.ModemState;
+import dan200.computercraft.shared.util.CapabilityUtil;
 import dan200.computercraft.shared.util.DirectionUtil;
 import dan200.computercraft.shared.util.NamedTileEntityType;
 import dan200.computercraft.shared.util.TickScheduler;
-import dan200.computercraft.shared.wired.CapabilityWiredElement;
 import net.minecraft.block.Block;
 import net.minecraft.block.BlockState;
 import net.minecraft.entity.player.PlayerEntity;
@@ -42,7 +41,10 @@ import javax.annotation.Nullable;
 import java.util.Collections;
 import java.util.Map;
 
-public class TileCable extends TileGeneric implements IPeripheralTile
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_WIRED_ELEMENT;
+
+public class TileCable extends TileGeneric
 {
     public static final NamedTileEntityType<TileCable> FACTORY = NamedTileEntityType.create(
         new ResourceLocation( ComputerCraft.MOD_ID, "cable" ),
@@ -82,7 +84,7 @@ public class TileCable extends TileGeneric implements IPeripheralTile
     }
 
     private boolean m_peripheralAccessAllowed;
-    private WiredModemLocalPeripheral m_peripheral = new WiredModemLocalPeripheral();
+    private final WiredModemLocalPeripheral m_peripheral = new WiredModemLocalPeripheral( this::refreshPeripheral );
 
     private boolean m_destroyed = false;
 
@@ -113,6 +115,7 @@ public class TileCable extends TileGeneric implements IPeripheralTile
             return new Vec3d( pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5 );
         }
     };
+    private LazyOptional<IPeripheral> modemCap;
 
     private final NonNullConsumer<LazyOptional<IWiredElement>> connectedNodeChanged = x -> connectionsChanged();
 
@@ -159,11 +162,8 @@ public class TileCable extends TileGeneric implements IPeripheralTile
     protected void invalidateCaps()
     {
         super.invalidateCaps();
-        if( elementCap != null )
+        elementCap = CapabilityUtil.invalidate( elementCap );
-        {
+        modemCap = CapabilityUtil.invalidate( modemCap );
-            elementCap.invalidate();
-            elementCap = null;
-        }
     }
 
     @Override
@@ -181,20 +181,26 @@ public class TileCable extends TileGeneric implements IPeripheralTile
         if( !world.isRemote ) world.getPendingBlockTicks().scheduleTick( pos, getBlockState().getBlock(), 0 );
     }
 
-    private void updateDirection()
+    private void refreshDirection()
-    {
-        if( !hasModemDirection )
     {
+        if( hasModemDirection ) return;
+
         hasModemDirection = true;
-            modemDirection = getDirection();
+        modemDirection = getBlockState().get( BlockCable.MODEM ).getFacing();
-        }
     }
 
+    @Nullable
+    private Direction getMaybeDirection()
+    {
+        refreshDirection();
+        return modemDirection;
+    }
+
+    @Nonnull
     private Direction getDirection()
     {
-        BlockState state = getBlockState();
+        refreshDirection();
-        Direction facing = state.get( BlockCable.MODEM ).getFacing();
+        return modemDirection == null ? Direction.NORTH : modemDirection;
-        return facing != null ? facing : Direction.NORTH;
     }
 
     @Override
@@ -232,11 +238,16 @@ public class TileCable extends TileGeneric implements IPeripheralTile
         if( !world.isRemote && m_peripheralAccessAllowed )
         {
             Direction facing = getDirection();
-            if( getPos().offset( facing ).equals( neighbour ) )
+            if( getPos().offset( facing ).equals( neighbour ) ) refreshPeripheral();
-            {
-                if( m_peripheral.attach( world, getPos(), facing ) ) updateConnectedPeripherals();
         }
     }
+
+    private void refreshPeripheral()
+    {
+        if( world != null && !isRemoved() && m_peripheral.attach( world, getPos(), getDirection() ) )
+        {
+            updateConnectedPeripherals();
+        }
     }
 
     @Nonnull
@@ -303,7 +314,14 @@ public class TileCable extends TileGeneric implements IPeripheralTile
     {
         if( getWorld().isRemote ) return;
 
-        updateDirection();
+        Direction oldDirection = modemDirection;
+        refreshDirection();
+        if( modemDirection != oldDirection )
+        {
+            // We invalidate both the modem and element if the modem's direction is different.
+            modemCap = CapabilityUtil.invalidate( modemCap );
+            elementCap = CapabilityUtil.invalidate( elementCap );
+        }
 
         if( m_modem.getModemState().pollChanged() ) updateBlockState();
 
@@ -353,11 +371,7 @@ public class TileCable extends TileGeneric implements IPeripheralTile
     void modemChanged()
     {
         // Tell anyone who cares that the connection state has changed
-        if( elementCap != null )
+        elementCap = CapabilityUtil.invalidate( elementCap );
-        {
-            elementCap.invalidate();
-            elementCap = null;
-        }
 
         if( getWorld().isRemote ) return;
 
@@ -415,22 +429,24 @@ public class TileCable extends TileGeneric implements IPeripheralTile
 
     @Nonnull
     @Override
-    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> capability, @Nullable Direction facing )
+    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> capability, @Nullable Direction side )
     {
-        if( capability == CapabilityWiredElement.CAPABILITY )
+        if( capability == CAPABILITY_WIRED_ELEMENT )
         {
-            if( m_destroyed || !BlockCable.canConnectIn( getBlockState(), facing ) ) return LazyOptional.empty();
+            if( m_destroyed || !BlockCable.canConnectIn( getBlockState(), side ) ) return LazyOptional.empty();
             if( elementCap == null ) elementCap = LazyOptional.of( () -> m_cable );
             return elementCap.cast();
         }
 
-        return super.getCapability( capability, facing );
+        if( capability == CAPABILITY_PERIPHERAL )
+        {
+            refreshDirection();
+            if( side != null && getMaybeDirection() != side ) return LazyOptional.empty();
+            if( modemCap == null ) modemCap = LazyOptional.of( () -> m_modem );
+            return modemCap.cast();
         }
 
-    @Override
+        return super.getCapability( capability, side );
-    public IPeripheral getPeripheral( @Nonnull Direction side )
-    {
-        return !m_destroyed && hasModem() && side == getDirection() ? m_modem : null;
     }
 
     boolean hasCable()

src/main/java/dan200/computercraft/shared/peripheral/modem/wired/TileWiredModemFull.java

@@ -11,14 +11,10 @@ import dan200.computercraft.api.ComputerCraftAPI;
 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.IPeripheralTile;
 import dan200.computercraft.shared.command.CommandCopy;
 import dan200.computercraft.shared.common.TileGeneric;
 import dan200.computercraft.shared.peripheral.modem.ModemState;
-import dan200.computercraft.shared.util.DirectionUtil;
+import dan200.computercraft.shared.util.*;
-import dan200.computercraft.shared.util.NamedTileEntityType;
-import dan200.computercraft.shared.util.TickScheduler;
-import dan200.computercraft.shared.wired.CapabilityWiredElement;
 import net.minecraft.block.BlockState;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.nbt.CompoundNBT;
@@ -40,10 +36,12 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.util.*;
 
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_WIRED_ELEMENT;
 import static dan200.computercraft.shared.peripheral.modem.wired.BlockWiredModemFull.MODEM_ON;
 import static dan200.computercraft.shared.peripheral.modem.wired.BlockWiredModemFull.PERIPHERAL_ON;
 
-public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
+public class TileWiredModemFull extends TileGeneric
 {
     public static final NamedTileEntityType<TileWiredModemFull> FACTORY = NamedTileEntityType.create(
         new ResourceLocation( ComputerCraft.MOD_ID, "wired_modem_full" ),
@@ -66,7 +64,7 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
         {
             for( int i = 0; i < 6; i++ )
             {
-                WiredModemPeripheral modem = m_entity.m_modems[i];
+                WiredModemPeripheral modem = m_entity.modems[i];
                 if( modem != null ) modem.attachPeripheral( name, peripheral );
             }
         }
@@ -76,7 +74,7 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
         {
             for( int i = 0; i < 6; i++ )
             {
-                WiredModemPeripheral modem = m_entity.m_modems[i];
+                WiredModemPeripheral modem = m_entity.modems[i];
                 if( modem != null ) modem.detachPeripheral( name );
             }
         }
@@ -97,10 +95,11 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
         }
     }
 
-    private WiredModemPeripheral[] m_modems = new WiredModemPeripheral[6];
+    private final WiredModemPeripheral[] modems = new WiredModemPeripheral[6];
+    private final SidedCaps<IPeripheral> modemCaps = SidedCaps.ofNonNull( this::getPeripheral );
 
     private boolean m_peripheralAccessAllowed = false;
-    private WiredModemLocalPeripheral[] m_peripherals = new WiredModemLocalPeripheral[6];
+    private final WiredModemLocalPeripheral[] m_peripherals = new WiredModemLocalPeripheral[6];
 
     private boolean m_destroyed = false;
     private boolean m_connectionsFormed = false;
@@ -115,7 +114,11 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
     public TileWiredModemFull()
     {
         super( FACTORY );
-        for( int i = 0; i < m_peripherals.length; i++ ) m_peripherals[i] = new WiredModemLocalPeripheral();
+        for( int i = 0; i < m_peripherals.length; i++ )
+        {
+            Direction facing = Direction.byIndex( i );
+            m_peripherals[i] = new WiredModemLocalPeripheral( () -> refreshPeripheral( facing ) );
+        }
     }
 
     private void doRemove()
@@ -149,11 +152,8 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
     protected void invalidateCaps()
     {
         super.invalidateCaps();
-        if( elementCap != null )
+        elementCap = CapabilityUtil.invalidate( elementCap );
-        {
+        modemCaps.invalidate();
-            elementCap.invalidate();
-            elementCap = null;
-        }
     }
 
     @Override
@@ -176,12 +176,17 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
         {
             for( Direction facing : DirectionUtil.FACINGS )
             {
-                if( getPos().offset( facing ).equals( neighbour ) )
+                if( getPos().offset( facing ).equals( neighbour ) ) refreshPeripheral( facing );
+            }
+        }
+    }
+
+    private void refreshPeripheral( @Nonnull Direction facing )
     {
         WiredModemLocalPeripheral peripheral = m_peripherals[facing.ordinal()];
-                    if( peripheral.attach( world, getPos(), facing ) ) updateConnectedPeripherals();
+        if( world != null && !isRemoved() && peripheral.attach( world, getPos(), facing ) )
-                }
+        {
-            }
+            updateConnectedPeripherals();
         }
     }
 
@@ -223,7 +228,7 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
     }
 
     @Override
-    public void read( CompoundNBT nbt )
+    public void read( @Nonnull CompoundNBT nbt )
     {
         super.read( nbt );
         m_peripheralAccessAllowed = nbt.getBoolean( NBT_PERIPHERAL_ENABLED );
@@ -362,14 +367,17 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
 
     @Nonnull
     @Override
-    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> capability, @Nullable Direction facing )
+    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> capability, @Nullable Direction side )
     {
-        if( capability == CapabilityWiredElement.CAPABILITY )
+        if( capability == CAPABILITY_WIRED_ELEMENT )
         {
             if( elementCap == null ) elementCap = LazyOptional.of( () -> m_element );
             return elementCap.cast();
         }
-        return super.getCapability( capability, facing );
+
+        if( capability == CAPABILITY_PERIPHERAL ) return modemCaps.get( side ).cast();
+
+        return super.getCapability( capability, side );
     }
 
     public IWiredElement getElement()
@@ -377,18 +385,13 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
         return m_element;
     }
 
-    // IPeripheralTile
+    private WiredModemPeripheral getPeripheral( @Nonnull Direction side )
-
-    @Override
-    public IPeripheral getPeripheral( @Nonnull Direction side )
     {
-        if( m_destroyed ) return null;
+        WiredModemPeripheral peripheral = modems[side.ordinal()];
+        if( peripheral != null ) return peripheral;
 
-        WiredModemPeripheral peripheral = m_modems[side.ordinal()];
-        if( peripheral == null )
-        {
         WiredModemLocalPeripheral localPeripheral = m_peripherals[side.ordinal()];
-            peripheral = m_modems[side.ordinal()] = new WiredModemPeripheral( m_modemState, m_element )
+        return modems[side.ordinal()] = new WiredModemPeripheral( m_modemState, m_element )
         {
             @Nonnull
             @Override
@@ -406,6 +409,4 @@ public class TileWiredModemFull extends TileGeneric implements IPeripheralTile
             }
         };
     }
-        return peripheral;
-    }
 }

src/main/java/dan200/computercraft/shared/peripheral/modem/wired/WiredModemLocalPeripheral.java

@@ -15,6 +15,8 @@ import net.minecraft.util.Direction;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.world.World;
 import net.minecraftforge.common.util.Constants;
+import net.minecraftforge.common.util.LazyOptional;
+import net.minecraftforge.common.util.NonNullConsumer;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -36,6 +38,12 @@ public final class WiredModemLocalPeripheral
     private String type;
 
     private IPeripheral peripheral;
+    private final NonNullConsumer<LazyOptional<IPeripheral>> invalidate;
+
+    public WiredModemLocalPeripheral( @Nonnull Runnable invalidate )
+    {
+        this.invalidate = x -> invalidate.run();
+    }
 
     /**
      * Attach a new peripheral from the world.
@@ -130,14 +138,15 @@ public final class WiredModemLocalPeripheral
             ? tag.getString( NBT_PERIPHERAL_TYPE + suffix ) : null;
     }
 
-    private static IPeripheral getPeripheralFrom( World world, BlockPos pos, Direction direction )
+    @Nullable
+    private IPeripheral getPeripheralFrom( World world, BlockPos pos, Direction direction )
     {
         BlockPos offset = pos.offset( direction );
 
         Block block = world.getBlockState( offset ).getBlock();
         if( block == ComputerCraft.Blocks.wiredModemFull || block == ComputerCraft.Blocks.cable ) return null;
 
-        IPeripheral peripheral = Peripherals.getPeripheral( world, offset, direction.getOpposite() );
+        IPeripheral peripheral = Peripherals.getPeripheral( world, offset, direction.getOpposite(), invalidate );
         return peripheral instanceof WiredModemPeripheral ? null : peripheral;
     }
 }

src/main/java/dan200/computercraft/shared/peripheral/modem/wireless/TileWirelessModem.java

@@ -7,10 +7,10 @@ package dan200.computercraft.shared.peripheral.modem.wireless;
 
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IPeripheral;
-import dan200.computercraft.api.peripheral.IPeripheralTile;
 import dan200.computercraft.shared.common.TileGeneric;
 import dan200.computercraft.shared.peripheral.modem.ModemPeripheral;
 import dan200.computercraft.shared.peripheral.modem.ModemState;
+import dan200.computercraft.shared.util.CapabilityUtil;
 import dan200.computercraft.shared.util.NamedTileEntityType;
 import dan200.computercraft.shared.util.TickScheduler;
 import net.minecraft.block.BlockState;
@@ -20,11 +20,15 @@ import net.minecraft.util.ResourceLocation;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.util.LazyOptional;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
-public class TileWirelessModem extends TileGeneric implements IPeripheralTile
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+
+public class TileWirelessModem extends TileGeneric
 {
     public static final NamedTileEntityType<TileWirelessModem> FACTORY_NORMAL = NamedTileEntityType.create(
         new ResourceLocation( ComputerCraft.MOD_ID, "wireless_modem_normal" ),
@@ -74,6 +78,7 @@ public class TileWirelessModem extends TileGeneric implements IPeripheralTile
     private Direction modemDirection = Direction.DOWN;
     private final ModemPeripheral modem;
     private boolean destroyed = false;
+    private LazyOptional<IPeripheral> modemCap;
 
     public TileWirelessModem( TileEntityType<? extends TileWirelessModem> type, boolean advanced )
     {
@@ -99,20 +104,6 @@ public class TileWirelessModem extends TileGeneric implements IPeripheralTile
         }
     }
 
-    @Override
-    public void markDirty()
-    {
-        super.markDirty();
-        if( world != null )
-        {
-            updateDirection();
-        }
-        else
-        {
-            hasModemDirection = false;
-        }
-    }
-
     @Override
     public void updateContainingBlockInfo()
     {
@@ -124,12 +115,17 @@ public class TileWirelessModem extends TileGeneric implements IPeripheralTile
     @Override
     public void blockTick()
     {
-        updateDirection();
+        Direction currentDirection = modemDirection;
+        refreshDirection();
+        // Invalidate the capability if the direction has changed. I'm not 100% happy with this implementation
+        //  - ideally we'd do it within refreshDirection or updateContainingBlockInfo, but this seems the _safest_
+        //  place.
+        if( currentDirection != modemDirection ) modemCap = CapabilityUtil.invalidate( modemCap );
 
         if( modem.getModemState().pollChanged() ) updateBlockState();
     }
 
-    private void updateDirection()
+    private void refreshDirection()
     {
         if( hasModemDirection ) return;
 
@@ -147,12 +143,18 @@ public class TileWirelessModem extends TileGeneric implements IPeripheralTile
         }
     }
 
-
+    @Nonnull
-    @Nullable
     @Override
-    public IPeripheral getPeripheral( @Nonnull Direction side )
+    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> cap, @Nullable Direction side )
     {
-        updateDirection();
+        if( cap == CAPABILITY_PERIPHERAL )
-        return side == modemDirection ? modem : null;
+        {
+            refreshDirection();
+            if( side != null && modemDirection != side ) return LazyOptional.empty();
+            if( modemCap == null ) modemCap = LazyOptional.of( () -> modem );
+            return modemCap.cast();
+        }
+
+        return super.getCapability( cap, side );
     }
 }

src/main/java/dan200/computercraft/shared/peripheral/monitor/TileMonitor.java

@@ -8,10 +8,10 @@ package dan200.computercraft.shared.peripheral.monitor;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IComputerAccess;
 import dan200.computercraft.api.peripheral.IPeripheral;
-import dan200.computercraft.api.peripheral.IPeripheralTile;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.shared.common.ServerTerminal;
 import dan200.computercraft.shared.common.TileGeneric;
+import dan200.computercraft.shared.util.CapabilityUtil;
 import dan200.computercraft.shared.util.NamedTileEntityType;
 import dan200.computercraft.shared.util.TickScheduler;
 import net.minecraft.entity.player.PlayerEntity;
@@ -26,12 +26,17 @@ import net.minecraft.util.math.AxisAlignedBB;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.BlockRayTraceResult;
 import net.minecraft.world.World;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.util.LazyOptional;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.HashSet;
 import java.util.Set;
 
-public class TileMonitor extends TileGeneric implements IPeripheralTile
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+
+public class TileMonitor extends TileGeneric
 {
     public static final NamedTileEntityType<TileMonitor> FACTORY_NORMAL = NamedTileEntityType.create(
         new ResourceLocation( ComputerCraft.MOD_ID, "monitor_normal" ),
@@ -59,7 +64,8 @@ public class TileMonitor extends TileGeneric implements IPeripheralTile
 
     private ServerMonitor m_serverMonitor;
     private ClientMonitor m_clientMonitor;
-    private MonitorPeripheral m_peripheral;
+    private MonitorPeripheral peripheral;
+    private LazyOptional<IPeripheral> peripheralCap;
     private final Set<IComputerAccess> m_computers = new HashSet<>();
 
     private boolean m_destroyed = false;
@@ -174,14 +180,25 @@ public class TileMonitor extends TileGeneric implements IPeripheralTile
         if( m_serverMonitor.pollTerminalChanged() ) updateBlock();
     }
 
-    // IPeripheralTile implementation
-
     @Override
-    public IPeripheral getPeripheral( @Nonnull Direction side )
+    protected void invalidateCaps()
+    {
+        super.invalidateCaps();
+        peripheralCap = CapabilityUtil.invalidate( peripheralCap );
+    }
+
+    @Nonnull
+    @Override
+    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> cap, @Nullable Direction side )
+    {
+        if( cap == CAPABILITY_PERIPHERAL )
         {
             createServerMonitor(); // Ensure the monitor is created before doing anything else.
-        if( m_peripheral == null ) m_peripheral = new MonitorPeripheral( this );
+            if( peripheral == null ) peripheral = new MonitorPeripheral( this );
-        return m_peripheral;
+            if( peripheralCap == null ) peripheralCap = LazyOptional.of( () -> peripheral );
+            return peripheralCap.cast();
+        }
+        return super.getCapability( cap, side );
     }
 
     public ServerMonitor getCachedServerMonitor()
@@ -409,7 +426,7 @@ public class TileMonitor extends TileGeneric implements IPeripheralTile
             for( int y = 0; y < height; y++ )
             {
                 TileMonitor monitor = getNeighbour( x, y );
-                if( monitor != null && monitor.m_peripheral != null )
+                if( monitor != null && monitor.peripheral != null )
                 {
                     needsTerminal = true;
                     break terminalCheck;

src/main/java/dan200/computercraft/shared/peripheral/printer/TilePrinter.java

@@ -7,14 +7,10 @@ package dan200.computercraft.shared.peripheral.printer;
 
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IPeripheral;
-import dan200.computercraft.api.peripheral.IPeripheralTile;
 import dan200.computercraft.core.terminal.Terminal;
 import dan200.computercraft.shared.common.TileGeneric;
 import dan200.computercraft.shared.media.items.ItemPrintout;
-import dan200.computercraft.shared.util.ColourUtils;
+import dan200.computercraft.shared.util.*;
-import dan200.computercraft.shared.util.DefaultSidedInventory;
-import dan200.computercraft.shared.util.NamedTileEntityType;
-import dan200.computercraft.shared.util.WorldUtil;
 import net.minecraft.block.BlockState;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.entity.player.PlayerInventory;
@@ -32,16 +28,17 @@ import net.minecraft.util.text.TranslationTextComponent;
 import net.minecraftforge.common.capabilities.Capability;
 import net.minecraftforge.common.util.LazyOptional;
 import net.minecraftforge.fml.network.NetworkHooks;
-import net.minecraftforge.items.IItemHandlerModifiable;
+import net.minecraftforge.items.IItemHandler;
 import net.minecraftforge.items.wrapper.InvWrapper;
 import net.minecraftforge.items.wrapper.SidedInvWrapper;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
 import static net.minecraftforge.items.CapabilityItemHandler.ITEM_HANDLER_CAPABILITY;
 
-public final class TilePrinter extends TileGeneric implements DefaultSidedInventory, IPeripheralTile, INameable, INamedContainerProvider
+public final class TilePrinter extends TileGeneric implements DefaultSidedInventory, INameable, INamedContainerProvider
 {
     public static final NamedTileEntityType<TilePrinter> FACTORY = NamedTileEntityType.create(
         new ResourceLocation( ComputerCraft.MOD_ID, "printer" ),
@@ -61,7 +58,9 @@ public final class TilePrinter extends TileGeneric implements DefaultSidedInvent
     ITextComponent customName;
 
     private final NonNullList<ItemStack> m_inventory = NonNullList.withSize( SLOTS, ItemStack.EMPTY );
-    private LazyOptional<IItemHandlerModifiable>[] itemHandlerCaps;
+    private final SidedCaps<IItemHandler> itemHandlerCaps =
+        SidedCaps.ofNullable( facing -> facing == null ? new InvWrapper( this ) : new SidedInvWrapper( this, facing ) );
+    private LazyOptional<IPeripheral> peripheralCap;
 
     private final Terminal m_page = new Terminal( ItemPrintout.LINE_MAX_LENGTH, ItemPrintout.LINES_PER_PAGE );
     private String m_pageTitle = "";
@@ -82,16 +81,8 @@ public final class TilePrinter extends TileGeneric implements DefaultSidedInvent
     protected void invalidateCaps()
     {
         super.invalidateCaps();
-
+        itemHandlerCaps.invalidate();
-        if( itemHandlerCaps != null )
+        peripheralCap = CapabilityUtil.invalidate( peripheralCap );
-        {
-            for( int i = 0; i < itemHandlerCaps.length; i++ )
-            {
-                if( itemHandlerCaps[i] == null ) continue;
-                itemHandlerCaps[i].invalidate();
-                itemHandlerCaps[i] = null;
-            }
-        }
     }
 
     @Nonnull
@@ -262,14 +253,6 @@ public final class TilePrinter extends TileGeneric implements DefaultSidedInvent
         }
     }
 
-    // IPeripheralTile implementation
-
-    @Override
-    public IPeripheral getPeripheral( @Nonnull Direction side )
-    {
-        return new PrinterPeripheral( this );
-    }
-
     @Nullable
     Terminal getCurrentPage()
     {
@@ -465,26 +448,15 @@ public final class TilePrinter extends TileGeneric implements DefaultSidedInvent
         getWorld().setBlockState( getPos(), state.with( BlockPrinter.TOP, top ).with( BlockPrinter.BOTTOM, bottom ) );
     }
 
-    @SuppressWarnings( { "unchecked", "rawtypes" } )
     @Nonnull
     @Override
     public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> capability, @Nullable Direction facing )
     {
-        if( capability == ITEM_HANDLER_CAPABILITY )
+        if( capability == ITEM_HANDLER_CAPABILITY ) return itemHandlerCaps.get( facing ).cast();
+        if( capability == CAPABILITY_PERIPHERAL )
         {
-            LazyOptional<IItemHandlerModifiable>[] handlers = itemHandlerCaps;
+            if( peripheralCap == null ) peripheralCap = LazyOptional.of( () -> new PrinterPeripheral( this ) );
-            if( handlers == null ) handlers = itemHandlerCaps = new LazyOptional[7];
+            return peripheralCap.cast();
-
-            int index = facing == null ? 0 : 1 + facing.getIndex();
-            LazyOptional<IItemHandlerModifiable> handler = handlers[index];
-            if( handler == null )
-            {
-                handler = handlers[index] = facing == null
-                    ? LazyOptional.of( () -> new InvWrapper( this ) )
-                    : LazyOptional.of( () -> new SidedInvWrapper( this, facing ) );
-            }
-
-            return handler.cast();
         }
 
         return super.getCapability( capability, facing );

src/main/java/dan200/computercraft/shared/peripheral/speaker/TileSpeaker.java

@@ -7,8 +7,8 @@ package dan200.computercraft.shared.peripheral.speaker;
 
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IPeripheral;
-import dan200.computercraft.api.peripheral.IPeripheralTile;
 import dan200.computercraft.shared.common.TileGeneric;
+import dan200.computercraft.shared.util.CapabilityUtil;
 import dan200.computercraft.shared.util.NamedTileEntityType;
 import net.minecraft.tileentity.ITickableTileEntity;
 import net.minecraft.util.Direction;
@@ -16,11 +16,15 @@ import net.minecraft.util.ResourceLocation;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
+import net.minecraftforge.common.capabilities.Capability;
+import net.minecraftforge.common.util.LazyOptional;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 
-public class TileSpeaker extends TileGeneric implements ITickableTileEntity, IPeripheralTile
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
+
+public class TileSpeaker extends TileGeneric implements ITickableTileEntity
 {
     public static final int MIN_TICKS_BETWEEN_SOUNDS = 1;
 
@@ -29,24 +33,39 @@ public class TileSpeaker extends TileGeneric implements ITickableTileEntity, IPe
         TileSpeaker::new
     );
 
-    private final SpeakerPeripheral m_peripheral;
+    private final SpeakerPeripheral peripheral;
+    private LazyOptional<IPeripheral> peripheralCap;
 
     public TileSpeaker()
     {
         super( FACTORY );
-        m_peripheral = new Peripheral( this );
+        peripheral = new Peripheral( this );
     }
 
     @Override
     public void tick()
     {
-        m_peripheral.update();
+        peripheral.update();
+    }
+
+    @Nonnull
+    @Override
+    public <T> LazyOptional<T> getCapability( @Nonnull Capability<T> cap, @Nullable Direction side )
+    {
+        if( cap == CAPABILITY_PERIPHERAL )
+        {
+            if( peripheralCap == null ) peripheralCap = LazyOptional.of( () -> peripheral );
+            return peripheralCap.cast();
+        }
+
+        return super.getCapability( cap, side );
     }
 
     @Override
-    public IPeripheral getPeripheral( @Nonnull Direction side )
+    protected void invalidateCaps()
     {
-        return m_peripheral;
+        super.invalidateCaps();
+        peripheralCap = CapabilityUtil.invalidate( peripheralCap );
     }
 
     private static final class Peripheral extends SpeakerPeripheral

src/main/java/dan200/computercraft/shared/proxy/ComputerCraftProxyCommon.java

@@ -8,7 +8,8 @@ package dan200.computercraft.shared.proxy;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.ComputerCraftAPI;
 import dan200.computercraft.api.media.IMedia;
-import dan200.computercraft.api.peripheral.IPeripheralTile;
+import dan200.computercraft.api.network.wired.IWiredElement;
+import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.core.computer.MainThread;
 import dan200.computercraft.core.tracking.Tracking;
 import dan200.computercraft.shared.command.CommandComputerCraft;
@@ -23,20 +24,18 @@ import dan200.computercraft.shared.data.HasComputerIdLootCondition;
 import dan200.computercraft.shared.data.PlayerCreativeLootCondition;
 import dan200.computercraft.shared.media.items.RecordMedia;
 import dan200.computercraft.shared.network.NetworkHandler;
-import dan200.computercraft.shared.peripheral.commandblock.CommandBlockPeripheral;
 import dan200.computercraft.shared.peripheral.modem.wireless.WirelessNetwork;
-import dan200.computercraft.shared.wired.CapabilityWiredElement;
+import dan200.computercraft.shared.util.NullStorage;
 import net.minecraft.inventory.container.Container;
 import net.minecraft.item.Item;
 import net.minecraft.item.MusicDiscItem;
-import net.minecraft.tileentity.CommandBlockTileEntity;
-import net.minecraft.tileentity.TileEntity;
 import net.minecraft.util.ResourceLocation;
 import net.minecraft.world.storage.loot.ConstantRange;
 import net.minecraft.world.storage.loot.LootPool;
 import net.minecraft.world.storage.loot.LootTables;
 import net.minecraft.world.storage.loot.TableLootEntry;
 import net.minecraft.world.storage.loot.conditions.LootConditionManager;
+import net.minecraftforge.common.capabilities.CapabilityManager;
 import net.minecraftforge.event.LootTableLoadEvent;
 import net.minecraftforge.event.TickEvent;
 import net.minecraftforge.event.entity.player.PlayerContainerEvent;
@@ -90,17 +89,6 @@ public final class ComputerCraftProxyCommon
 
     private static void registerProviders()
     {
-        // Register peripheral providers
-        ComputerCraftAPI.registerPeripheralProvider( ( world, pos, side ) -> {
-            TileEntity tile = world.getTileEntity( pos );
-            return tile instanceof IPeripheralTile ? ((IPeripheralTile) tile).getPeripheral( side ) : null;
-        } );
-
-        ComputerCraftAPI.registerPeripheralProvider( ( world, pos, side ) -> {
-            TileEntity tile = world.getTileEntity( pos );
-            return ComputerCraft.enableCommandBlock && tile instanceof CommandBlockTileEntity ? new CommandBlockPeripheral( (CommandBlockTileEntity) tile ) : null;
-        } );
-
         // Register bundled power providers
         ComputerCraftAPI.registerBundledRedstoneProvider( new DefaultBundledRedstoneProvider() );
 
@@ -112,8 +100,9 @@ public final class ComputerCraftProxyCommon
             return null;
         } );
 
-        // Register network providers
+        // Register capabilities
-        CapabilityWiredElement.register();
+        CapabilityManager.INSTANCE.register( IWiredElement.class, new NullStorage<>(), () -> null );
+        CapabilityManager.INSTANCE.register( IPeripheral.class, new NullStorage<>(), () -> null );
     }
 
     @Mod.EventBusSubscriber( modid = ComputerCraft.MOD_ID )

src/main/java/dan200/computercraft/shared/turtle/blocks/TileTurtle.java

@@ -47,6 +47,7 @@ import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import java.util.Collections;
 
+import static dan200.computercraft.shared.Capabilities.CAPABILITY_PERIPHERAL;
 import static net.minecraftforge.items.CapabilityItemHandler.ITEM_HANDLER_CAPABILITY;
 
 public class TileTurtle extends TileComputerBase implements ITurtleTile, DefaultInventory
@@ -79,6 +80,7 @@ public class TileTurtle extends TileComputerBase implements ITurtleTile, Default
     private boolean m_inventoryChanged = false;
     private TurtleBrain m_brain = new TurtleBrain( this );
     private MoveState m_moveState = MoveState.NOT_MOVED;
+    private LazyOptional<IPeripheral> peripheral;
 
     public TileTurtle( TileEntityType<? extends TileGeneric> type, ComputerFamily family )
     {
@@ -103,7 +105,6 @@ public class TileTurtle extends TileComputerBase implements ITurtleTile, Default
         return computer;
     }
 
-    @Override
     public ComputerProxy createProxy()
     {
         return m_brain.getProxy();
@@ -154,11 +155,8 @@ public class TileTurtle extends TileComputerBase implements ITurtleTile, Default
     protected void invalidateCaps()
     {
         super.invalidateCaps();
-        if( itemHandlerCap != null )
+        itemHandlerCap = CapabilityUtil.invalidate( itemHandlerCap );
-        {
+        peripheral = CapabilityUtil.invalidate( peripheral );
-            itemHandlerCap.invalidate();
-            itemHandlerCap = null;
-        }
     }
 
     @Nonnull
@@ -545,14 +543,10 @@ public class TileTurtle extends TileComputerBase implements ITurtleTile, Default
         m_inventoryChanged = copy.m_inventoryChanged;
         m_brain = copy.m_brain;
         m_brain.setOwner( this );
-        copy.m_moveState = MoveState.MOVED;
-    }
 
-    @Nullable
+        // Mark the other turtle as having moved, and so its peripheral is dead.
-    @Override
+        copy.m_moveState = MoveState.MOVED;
-    public IPeripheral getPeripheral( @Nonnull Direction side )
+        copy.peripheral = CapabilityUtil.invalidate( copy.peripheral );
-    {
-        return hasMoved() ? null : new ComputerPeripheral( "turtle", createProxy() );
     }
 
     public IItemHandlerModifiable getItemHandler()
@@ -569,6 +563,17 @@ public class TileTurtle extends TileComputerBase implements ITurtleTile, Default
             if( itemHandlerCap == null ) itemHandlerCap = LazyOptional.of( () -> new InvWrapper( this ) );
             return itemHandlerCap.cast();
         }
+
+        if( cap == CAPABILITY_PERIPHERAL )
+        {
+            if( hasMoved() ) return LazyOptional.empty();
+            if( peripheral == null )
+            {
+                peripheral = LazyOptional.of( () -> new ComputerPeripheral( "turtle", createProxy() ) );
+            }
+            return peripheral.cast();
+        }
+
         return super.getCapability( cap, side );
     }
 

src/main/java/dan200/computercraft/shared/turtle/core/TurtleBrain.java

@@ -15,7 +15,6 @@ import dan200.computercraft.api.turtle.*;
 import dan200.computercraft.core.computer.ComputerSide;
 import dan200.computercraft.shared.TurtleUpgrades;
 import dan200.computercraft.shared.computer.blocks.ComputerProxy;
-import dan200.computercraft.shared.computer.blocks.TileComputerBase;
 import dan200.computercraft.shared.computer.core.ComputerFamily;
 import dan200.computercraft.shared.computer.core.ServerComputer;
 import dan200.computercraft.shared.turtle.blocks.TileTurtle;
@@ -72,12 +71,12 @@ public class TurtleBrain implements ITurtleAccess
     private final IInventory m_inventory = (InventoryDelegate) () -> m_owner;
     private final IItemHandlerModifiable m_inventoryWrapper = new InvWrapper( m_inventory );
 
-    private Queue<TurtleCommandQueueEntry> m_commandQueue = new ArrayDeque<>();
+    private final Queue<TurtleCommandQueueEntry> m_commandQueue = new ArrayDeque<>();
     private int m_commandsIssued = 0;
 
-    private Map<TurtleSide, ITurtleUpgrade> m_upgrades = new EnumMap<>( TurtleSide.class );
+    private final Map<TurtleSide, ITurtleUpgrade> m_upgrades = new EnumMap<>( TurtleSide.class );
-    private Map<TurtleSide, IPeripheral> peripherals = new EnumMap<>( TurtleSide.class );
+    private final Map<TurtleSide, IPeripheral> peripherals = new EnumMap<>( TurtleSide.class );
-    private Map<TurtleSide, CompoundNBT> m_upgradeNBTData = new EnumMap<>( TurtleSide.class );
+    private final Map<TurtleSide, CompoundNBT> m_upgradeNBTData = new EnumMap<>( TurtleSide.class );
 
     private int m_selectedSlot = 0;
     private int m_fuelLevel = 0;
@@ -107,17 +106,7 @@ public class TurtleBrain implements ITurtleAccess
 
     public ComputerProxy getProxy()
     {
-        if( m_proxy == null )
+        if( m_proxy == null ) m_proxy = new ComputerProxy( () -> m_owner );
-        {
-            m_proxy = new ComputerProxy()
-            {
-                @Override
-                protected TileComputerBase getTile()
-                {
-                    return m_owner;
-                }
-            };
-        }
         return m_proxy;
     }
 

src/main/java/dan200/computercraft/shared/util/CapabilityUtil.java

@@ -0,0 +1,47 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.util;
+
+import net.minecraftforge.common.util.LazyOptional;
+import net.minecraftforge.common.util.NonNullConsumer;
+
+import javax.annotation.Nullable;
+
+public final class CapabilityUtil
+{
+    private CapabilityUtil()
+    {
+    }
+
+    @Nullable
+    public static <T> LazyOptional<T> invalidate( @Nullable LazyOptional<T> cap )
+    {
+        if( cap != null ) cap.invalidate();
+        return null;
+    }
+
+    public static <T> void invalidate( @Nullable LazyOptional<T>[] caps )
+    {
+        if( caps == null ) return;
+
+        for( int i = 0; i < caps.length; i++ )
+        {
+            LazyOptional<T> cap = caps[i];
+            if( cap != null ) cap.invalidate();
+            caps[i] = null;
+        }
+    }
+
+    @Nullable
+    public static <T> T unwrap( LazyOptional<T> p, NonNullConsumer<LazyOptional<T>> invalidate )
+    {
+        if( !p.isPresent() ) return null;
+
+        p.addListener( invalidate );
+        return p.orElseThrow( NullPointerException::new );
+    }
+}

src/main/java/dan200/computercraft/shared/util/NullStorage.java

@@ -0,0 +1,25 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.util;
+
+import net.minecraft.nbt.INBT;
+import net.minecraft.util.Direction;
+import net.minecraftforge.common.capabilities.Capability;
+
+public class NullStorage<T> implements Capability.IStorage<T>
+{
+    @Override
+    public INBT writeNBT( Capability<T> capability, T instance, Direction side )
+    {
+        return null;
+    }
+
+    @Override
+    public void readNBT( Capability<T> capability, T instance, Direction side, INBT base )
+    {
+    }
+}

src/main/java/dan200/computercraft/shared/util/SidedCaps.java

@@ -0,0 +1,68 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+
+package dan200.computercraft.shared.util;
+
+import net.minecraft.util.Direction;
+import net.minecraftforge.common.util.LazyOptional;
+
+import javax.annotation.Nullable;
+import java.util.function.Function;
+
+/**
+ * Provides a constant (but invalidate-able) capability for each side.
+ *
+ * @param <T> The type of the produced capability.
+ */
+public final class SidedCaps<T>
+{
+    private final Function<Direction, T> factory;
+    private final boolean allowNull;
+    private T[] values;
+    private LazyOptional<T>[] caps;
+
+    private SidedCaps( Function<Direction, T> factory, boolean allowNull )
+    {
+        this.factory = factory;
+        this.allowNull = allowNull;
+    }
+
+    public static <T> SidedCaps<T> ofNonNull( Function<Direction, T> factory )
+    {
+        return new SidedCaps<>( factory, false );
+    }
+
+    public static <T> SidedCaps<T> ofNullable( Function<Direction, T> factory )
+    {
+        return new SidedCaps<>( factory, true );
+    }
+
+    @SuppressWarnings( { "unchecked", "rawtypes" } )
+    public LazyOptional<T> get( @Nullable Direction direction )
+    {
+        if( direction == null && !allowNull ) return LazyOptional.empty();
+        int index = direction == null ? 6 : direction.ordinal();
+
+        LazyOptional<T>[] caps = this.caps;
+        if( caps == null )
+        {
+            caps = this.caps = new LazyOptional[allowNull ? 7 : 6];
+            values = (T[]) new Object[caps.length];
+        }
+
+        LazyOptional<T> cap = caps[index];
+        return cap == null ? caps[index] = LazyOptional.of( () -> {
+            T[] values = this.values;
+            T value = values[index];
+            return value == null ? values[index] = factory.apply( direction ) : value;
+        } ) : cap;
+    }
+
+    public void invalidate()
+    {
+        if( caps != null ) CapabilityUtil.invalidate( caps );
+    }
+}

src/main/java/dan200/computercraft/shared/wired/CapabilityWiredElement.java

@@ -1,87 +0,0 @@
-/*
- * This file is part of ComputerCraft - http://www.computercraft.info
- * Copyright Daniel Ratcliffe, 2011-2020. Do not distribute without permission.
- * Send enquiries to dratcliffe@gmail.com
- */
-package dan200.computercraft.shared.wired;
-
-import dan200.computercraft.api.network.wired.IWiredElement;
-import dan200.computercraft.api.network.wired.IWiredNode;
-import net.minecraft.nbt.INBT;
-import net.minecraft.util.Direction;
-import net.minecraft.util.math.Vec3d;
-import net.minecraft.world.World;
-import net.minecraftforge.common.capabilities.Capability;
-import net.minecraftforge.common.capabilities.CapabilityInject;
-import net.minecraftforge.common.capabilities.CapabilityManager;
-import net.minecraftforge.common.util.LazyOptional;
-
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-
-public final class CapabilityWiredElement
-{
-    @CapabilityInject( IWiredElement.class )
-    public static Capability<IWiredElement> CAPABILITY = null;
-
-    private CapabilityWiredElement() {}
-
-    public static void register()
-    {
-        CapabilityManager.INSTANCE.register( IWiredElement.class, new NullStorage(), NullElement::new );
-    }
-
-    private static class NullElement implements IWiredElement
-    {
-        @Nonnull
-        @Override
-        public IWiredNode getNode()
-        {
-            throw new IllegalStateException( "Should not use the default element implementation" );
-        }
-
-        @Nonnull
-        @Override
-        public World getWorld()
-        {
-            throw new IllegalStateException( "Should not use the default element implementation" );
-        }
-
-        @Nonnull
-        @Override
-        public Vec3d getPosition()
-        {
-            throw new IllegalStateException( "Should not use the default element implementation" );
-        }
-
-        @Nonnull
-        @Override
-        public String getSenderID()
-        {
-            throw new IllegalStateException( "Should not use the default element implementation" );
-        }
-    }
-
-    private static class NullStorage implements Capability.IStorage<IWiredElement>
-    {
-        @Override
-        public INBT writeNBT( Capability<IWiredElement> capability, IWiredElement instance, Direction side )
-        {
-            return null;
-        }
-
-        @Override
-        public void readNBT( Capability<IWiredElement> capability, IWiredElement instance, Direction side, INBT base )
-        {
-        }
-    }
-
-    private static final IWiredElement NULL_ELEMENT = new NullElement();
-
-    @Nullable
-    public static IWiredElement unwrap( LazyOptional<IWiredElement> capability )
-    {
-        IWiredElement element = capability.orElse( NULL_ELEMENT );
-        return element == NULL_ELEMENT ? null : element;
-    }
-}