Generic peripherals for any tile entities (#478)

This exposes a basic peripheral for any tile entity which does not have methods
already registered. We currently provide the following methods:

 - Inventories: size, list, getItemMeta, pushItems, pullItems.
 - Energy storage: getEnergy, getEnergyCapacity
 - Fluid tanks: tanks(), pushFluid, pullFluid.

These methods are currently experimental - it must be enabled through 
`experimental.generic_peripherals`. While this is an initial step towards
implementing #452, but is by no means complete.

build.gradle

@@ -105,6 +105,9 @@ dependencies {
 
     runtimeOnly fg.deobf("mezz.jei:jei-1.15.2:6.0.0.3")
 
+    compileOnly 'com.google.auto.service:auto-service:1.0-rc7'
+    annotationProcessor 'com.google.auto.service:auto-service:1.0-rc7'
+
     shade 'org.squiddev:Cobalt:0.5.1-SNAPSHOT'
 
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.4.2'

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

@@ -38,8 +38,6 @@ public final class ComputerCraft
 {
     public static final String MOD_ID = "computercraft";
 
-    public static final int DATAFIXER_VERSION = 0;
-
     // Configuration options
     public static final String[] DEFAULT_HTTP_ALLOW = new String[] { "*" };
     public static final String[] DEFAULT_HTTP_DENY = new String[] {
@@ -93,6 +91,8 @@ public final class ComputerCraft
     public static boolean turtlesCanPush = true;
     public static EnumSet<TurtleAction> turtleDisabledActions = EnumSet.noneOf( TurtleAction.class );
 
+    public static boolean genericPeripheral = false;
+
     public static final int terminalWidth_computer = 51;
     public static final int terminalHeight_computer = 19;
 

src/main/java/dan200/computercraft/core/asm/Generator.java

@@ -34,7 +34,7 @@ import java.util.function.Function;
 
 import static org.objectweb.asm.Opcodes.*;
 
-public class Generator<T>
+public final class Generator<T>
 {
     private static final AtomicInteger METHOD_ID = new AtomicInteger();
 
@@ -99,26 +99,28 @@ public class Generator<T>
             LuaFunction annotation = method.getAnnotation( LuaFunction.class );
             if( annotation == null ) continue;
 
+            if( Modifier.isStatic( method.getModifiers() ) )
+            {
+                ComputerCraft.log.warn( "LuaFunction method {}.{} should be an instance method.", method.getDeclaringClass(), method.getName() );
+                continue;
+            }
+
             T instance = methodCache.getUnchecked( method ).orElse( null );
             if( instance == null ) continue;
 
             if( methods == null ) methods = new ArrayList<>();
+            addMethod( methods, method, annotation, instance );
+        }
 
-            if( annotation.mainThread() ) instance = wrap.apply( instance );
+        for( GenericSource.GenericMethod method : GenericSource.GenericMethod.all() )
+        {
+            if( !method.target.isAssignableFrom( klass ) ) continue;
 
-            String[] names = annotation.value();
-            boolean isSimple = method.getReturnType() != MethodResult.class && !annotation.mainThread();
-            if( names.length == 0 )
-            {
-                methods.add( new NamedMethod<>( method.getName(), instance, isSimple ) );
-            }
-            else
-            {
-                for( String name : names )
-                {
-                    methods.add( new NamedMethod<>( name, instance, isSimple ) );
-                }
-            }
+            T instance = methodCache.getUnchecked( method.method ).orElse( null );
+            if( instance == null ) continue;
+
+            if( methods == null ) methods = new ArrayList<>();
+            addMethod( methods, method.method, method.annotation, instance );
         }
 
         if( methods == null ) return Collections.emptyList();
@@ -126,19 +128,40 @@ public class Generator<T>
         return Collections.unmodifiableList( methods );
     }
 
+    private void addMethod( List<NamedMethod<T>> methods, Method method, LuaFunction annotation, T instance )
+    {
+        if( annotation.mainThread() ) instance = wrap.apply( instance );
+
+        String[] names = annotation.value();
+        boolean isSimple = method.getReturnType() != MethodResult.class && !annotation.mainThread();
+        if( names.length == 0 )
+        {
+            methods.add( new NamedMethod<>( method.getName(), instance, isSimple ) );
+        }
+        else
+        {
+            for( String name : names )
+            {
+                methods.add( new NamedMethod<>( name, instance, isSimple ) );
+            }
+        }
+    }
+
     @Nonnull
     private Optional<T> build( Method method )
     {
         String name = method.getDeclaringClass().getName() + "." + method.getName();
         int modifiers = method.getModifiers();
-        if( !Modifier.isFinal( modifiers ) )
+
+        // Instance methods must be final - this prevents them being overridden and potentially exposed twice.
+        if( !Modifier.isStatic( modifiers ) && !Modifier.isFinal( modifiers ) )
         {
             ComputerCraft.log.warn( "Lua Method {} should be final.", name );
         }
 
-        if( Modifier.isStatic( modifiers ) || !Modifier.isPublic( modifiers ) )
+        if( !Modifier.isPublic( modifiers ) )
         {
-            ComputerCraft.log.error( "Lua Method {} should be a public instance method.", name );
+            ComputerCraft.log.error( "Lua Method {} should be a public method.", name );
             return Optional.empty();
         }
 
@@ -160,10 +183,14 @@ public class Generator<T>
             }
         }
 
+        // We have some rather ugly handling of static methods in both here and the main generate function. Static methods
+        // only come from generic sources, so this should be safe.
+        Class<?> target = Modifier.isStatic( modifiers ) ? method.getParameterTypes()[0] : method.getDeclaringClass();
+
         try
         {
             String className = method.getDeclaringClass().getName() + "$cc$" + method.getName() + METHOD_ID.getAndIncrement();
-            byte[] bytes = generate( className, method );
+            byte[] bytes = generate( className, target, method );
             if( bytes == null ) return Optional.empty();
 
             Class<?> klass = DeclaringClassLoader.INSTANCE.define( className, bytes, method.getDeclaringClass().getProtectionDomain() );
@@ -178,7 +205,7 @@ public class Generator<T>
     }
 
     @Nullable
-    private byte[] generate( String className, Method method )
+    private byte[] generate( String className, Class<?> target, Method method )
     {
         String internalName = className.replace( ".", "/" );
 
@@ -200,19 +227,27 @@ public class Generator<T>
         {
             MethodVisitor mw = cw.visitMethod( ACC_PUBLIC, METHOD_NAME, methodDesc, null, EXCEPTIONS );
             mw.visitCode();
-            mw.visitVarInsn( ALOAD, 1 );
-            mw.visitTypeInsn( CHECKCAST, Type.getInternalName( method.getDeclaringClass() ) );
+
+            // If we're an instance method, load the this parameter.
+            if( !Modifier.isStatic( method.getModifiers() ) )
+            {
+                mw.visitVarInsn( ALOAD, 1 );
+                mw.visitTypeInsn( CHECKCAST, Type.getInternalName( target ) );
+            }
 
             int argIndex = 0;
             for( java.lang.reflect.Type genericArg : method.getGenericParameterTypes() )
             {
-                Boolean loadedArg = loadArg( mw, method, genericArg, argIndex );
+                Boolean loadedArg = loadArg( mw, target, method, genericArg, argIndex );
                 if( loadedArg == null ) return null;
                 if( loadedArg ) argIndex++;
             }
 
-            mw.visitMethodInsn( INVOKEVIRTUAL, Type.getInternalName( method.getDeclaringClass() ), method.getName(),
-                Type.getMethodDescriptor( method ), false );
+            mw.visitMethodInsn(
+                Modifier.isStatic( method.getModifiers() ) ? INVOKESTATIC : INVOKEVIRTUAL,
+                Type.getInternalName( method.getDeclaringClass() ), method.getName(),
+                Type.getMethodDescriptor( method ), false
+            );
 
             // We allow a reasonable amount of flexibility on the return value's type. Alongside the obvious MethodResult,
             // we convert basic types into an immediate result.
@@ -250,8 +285,15 @@ public class Generator<T>
         return cw.toByteArray();
     }
 
-    private Boolean loadArg( MethodVisitor mw, Method method, java.lang.reflect.Type genericArg, int argIndex )
+    private Boolean loadArg( MethodVisitor mw, Class<?> target, Method method, java.lang.reflect.Type genericArg, int argIndex )
     {
+        if( genericArg == target )
+        {
+            mw.visitVarInsn( ALOAD, 1 );
+            mw.visitTypeInsn( CHECKCAST, Type.getInternalName( target ) );
+            return false;
+        }
+
         Class<?> arg = Reflect.getRawType( method, genericArg, true );
         if( arg == null ) return null;
 

src/main/java/dan200/computercraft/core/asm/GenericSource.java

@@ -0,0 +1,100 @@
+/*
+ * 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.core.asm;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.shared.peripheral.generic.GenericPeripheralProvider;
+import net.minecraft.util.ResourceLocation;
+
+import javax.annotation.Nonnull;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.lang.reflect.Type;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.ServiceLoader;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * A generic source of {@link LuaMethod} functions. This allows for injecting methods onto objects you do not own.
+ *
+ * Unlike conventional Lua objects, the annotated methods should be {@code static}, with their target as the first
+ * parameter.
+ *
+ * This is used by the generic peripheral system ({@link GenericPeripheralProvider}) to provide methods for arbitrary
+ * tile entities. Eventually this'll be be exposed in the public API. Until it is stabilised, it will remain in this
+ * package - do not use it in external mods!
+ */
+public interface GenericSource
+{
+    /**
+     * A unique identifier for this generic source. This may be used in the future to allow disabling specific sources.
+     *
+     * @return This source's identifier.
+     */
+    @Nonnull
+    ResourceLocation id();
+
+    /**
+     * A generic method is a method belonging to a {@link GenericSource} with a known target.
+     */
+    class GenericMethod
+    {
+        final Method method;
+        final LuaFunction annotation;
+        final Class<?> target;
+
+        private static List<GenericMethod> cache;
+
+        GenericMethod( Method method, LuaFunction annotation, Class<?> target )
+        {
+            this.method = method;
+            this.annotation = annotation;
+            this.target = target;
+        }
+
+        /**
+         * Find all public static methods annotated with {@link LuaFunction} which belong to a {@link GenericSource}.
+         *
+         * @return All available generic methods.
+         */
+        static List<GenericMethod> all()
+        {
+            if( cache != null ) return cache;
+            return cache = StreamSupport
+                .stream( ServiceLoader.load( GenericSource.class, GenericSource.class.getClassLoader() ).spliterator(), false )
+                .flatMap( x -> Arrays.stream( x.getClass().getDeclaredMethods() ) )
+                .map( method -> {
+                    LuaFunction annotation = method.getAnnotation( LuaFunction.class );
+                    if( annotation == null ) return null;
+
+                    if( !Modifier.isStatic( method.getModifiers() ) )
+                    {
+                        ComputerCraft.log.error( "GenericSource method {}.{} should be static.", method.getDeclaringClass(), method.getName() );
+                        return null;
+                    }
+
+                    Type[] types = method.getGenericParameterTypes();
+                    if( types.length == 0 )
+                    {
+                        ComputerCraft.log.error( "GenericSource method {}.{} has no parameters.", method.getDeclaringClass(), method.getName() );
+                        return null;
+                    }
+
+                    Class<?> target = Reflect.getRawType( method, types[0], false );
+                    if( target == null ) return null;
+
+                    return new GenericMethod( method, annotation, target );
+                } )
+                .filter( Objects::nonNull )
+                .collect( Collectors.toList() );
+        }
+    }
+}

src/main/java/dan200/computercraft/core/asm/LuaMethod.java

@@ -14,10 +14,8 @@ import java.util.Collections;
 public interface LuaMethod
 {
     Generator<LuaMethod> GENERATOR = new Generator<>( LuaMethod.class, Collections.singletonList( ILuaContext.class ),
-        m -> ( target, context, args ) -> {
-            long id = context.issueMainThreadTask( () -> TaskCallback.checkUnwrap( m.apply( target, context, args ) ) );
-            return new TaskCallback( id ).pull;
-        } );
+        m -> ( target, context, args ) -> TaskCallback.make( context, () -> TaskCallback.checkUnwrap( m.apply( target, context, args ) ) )
+    );
 
     IntCache<LuaMethod> DYNAMIC = new IntCache<>(
         method -> ( instance, context, args ) -> ((IDynamicLuaObject) instance).callMethod( context, method, args )

src/main/java/dan200/computercraft/core/asm/NamedMethod.java

@@ -8,7 +8,7 @@ package dan200.computercraft.core.asm;
 
 import javax.annotation.Nonnull;
 
-public class NamedMethod<T>
+public final class NamedMethod<T>
 {
     private final String name;
     private final T method;

src/main/java/dan200/computercraft/core/asm/PeripheralMethod.java

@@ -19,10 +19,8 @@ import java.util.Arrays;
 public interface PeripheralMethod
 {
     Generator<PeripheralMethod> GENERATOR = new Generator<>( PeripheralMethod.class, Arrays.asList( ILuaContext.class, IComputerAccess.class ),
-        m -> ( target, context, computer, args ) -> {
-            long id = context.issueMainThreadTask( () -> TaskCallback.checkUnwrap( m.apply( target, context, computer, args ) ) );
-            return new TaskCallback( id ).pull;
-        } );
+        m -> ( target, context, computer, args ) -> TaskCallback.make( context, () -> TaskCallback.checkUnwrap( m.apply( target, context, computer, args ) ) )
+    );
 
     IntCache<PeripheralMethod> DYNAMIC = new IntCache<>(
         method -> ( instance, context, computer, args ) -> ((IDynamicPeripheral) instance).callMethod( computer, context, method, args )

src/main/java/dan200/computercraft/core/asm/TaskCallback.java

@@ -6,19 +6,17 @@
 
 package dan200.computercraft.core.asm;
 
-import dan200.computercraft.api.lua.ILuaCallback;
-import dan200.computercraft.api.lua.LuaException;
-import dan200.computercraft.api.lua.MethodResult;
+import dan200.computercraft.api.lua.*;
 
 import javax.annotation.Nonnull;
 import java.util.Arrays;
 
-class TaskCallback implements ILuaCallback
+public final class TaskCallback implements ILuaCallback
 {
-    final MethodResult pull = MethodResult.pullEvent( "task_complete", this );
+    private final MethodResult pull = MethodResult.pullEvent( "task_complete", this );
     private final long task;
 
-    TaskCallback( long task )
+    private TaskCallback( long task )
     {
         this.task = task;
     }
@@ -55,4 +53,10 @@ class TaskCallback implements ILuaCallback
         if( result.getCallback() != null ) throw new IllegalStateException( "Cannot return MethodResult currently" );
         return result.getResult();
     }
+
+    public static MethodResult make( ILuaContext context, ILuaTask func ) throws LuaException
+    {
+        long task = context.issueMainThreadTask( func );
+        return new TaskCallback( task ).pull;
+    }
 }

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

@@ -73,6 +73,8 @@ public final class Config
     private static final ConfigValue<Boolean> turtlesCanPush;
     private static final ConfigValue<List<? extends String>> turtleDisabledActions;
 
+    private static final ConfigValue<Boolean> genericPeripheral;
+
     private static final ConfigValue<MonitorRenderer> monitorRenderer;
 
     private static final ForgeConfigSpec serverSpec;
@@ -260,6 +262,17 @@ public final class Config
             builder.pop();
         }
 
+        {
+            builder.comment( "Options for various experimental features. These are not guaranteed to be stable, and may change or be removed across versions." );
+            builder.push( "experimental" );
+
+            genericPeripheral = builder
+                .comment( "Attempt to make any existing block (or tile entity) a peripheral.\n" +
+                    "This provides peripheral methods for any inventory, fluid tank or energy storage block. It will" +
+                    "_not_ provide methods which have an existing peripheral provider." )
+                .define( "generic_peripherals", false );
+        }
+
         serverSpec = builder.build();
 
         Builder clientBuilder = new Builder();
@@ -322,6 +335,8 @@ public final class Config
         ComputerCraft.turtleDisabledActions.clear();
         for( String value : turtleDisabledActions.get() ) ComputerCraft.turtleDisabledActions.add( getAction( value ) );
 
+        ComputerCraft.genericPeripheral = genericPeripheral.get();
+
         // Client
         ComputerCraft.monitorRenderer = monitorRenderer.get();
     }

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

@@ -8,6 +8,7 @@ package dan200.computercraft.shared;
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.api.peripheral.IPeripheral;
 import dan200.computercraft.api.peripheral.IPeripheralProvider;
+import dan200.computercraft.shared.peripheral.generic.GenericPeripheralProvider;
 import dan200.computercraft.shared.util.CapabilityUtil;
 import net.minecraft.tileentity.TileEntity;
 import net.minecraft.util.Direction;
@@ -66,7 +67,7 @@ public final class Peripherals
             }
         }
 
-        return null;
+        return CapabilityUtil.unwrap( GenericPeripheralProvider.getPeripheral( world, pos, side ), invalidate );
     }
 
 }

src/main/java/dan200/computercraft/shared/peripheral/generic/GenericPeripheral.java

@@ -0,0 +1,76 @@
+/*
+ * 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.peripheral.generic;
+
+import dan200.computercraft.api.lua.IArguments;
+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.IDynamicPeripheral;
+import dan200.computercraft.api.peripheral.IPeripheral;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.ResourceLocation;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.List;
+
+class GenericPeripheral implements IDynamicPeripheral
+{
+    private final String type;
+    private final TileEntity tile;
+    private final List<SaturatedMethod> methods;
+
+    GenericPeripheral( TileEntity tile, List<SaturatedMethod> methods )
+    {
+        ResourceLocation type = tile.getType().getRegistryName();
+        this.tile = tile;
+        this.type = type == null ? "unknown" : type.toString();
+        this.methods = methods;
+    }
+
+    @Nonnull
+    @Override
+    public String[] getMethodNames()
+    {
+        String[] names = new String[methods.size()];
+        for( int i = 0; i < methods.size(); i++ ) names[i] = methods.get( i ).getName();
+        return names;
+    }
+
+    @Nonnull
+    @Override
+    public MethodResult callMethod( @Nonnull IComputerAccess computer, @Nonnull ILuaContext context, int method, @Nonnull IArguments arguments ) throws LuaException
+    {
+        return methods.get( method ).apply( context, computer, arguments );
+    }
+
+    @Nonnull
+    @Override
+    public String getType()
+    {
+        return type;
+    }
+
+    @Nullable
+    @Override
+    public Object getTarget()
+    {
+        return tile;
+    }
+
+    @Override
+    public boolean equals( @Nullable IPeripheral other )
+    {
+        if( other == this ) return true;
+        if( !(other instanceof GenericPeripheral) ) return false;
+
+        GenericPeripheral generic = (GenericPeripheral) other;
+        return tile == generic.tile && methods.equals( generic.methods );
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/GenericPeripheralProvider.java

@@ -0,0 +1,72 @@
+/*
+ * 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.peripheral.generic;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.core.asm.NamedMethod;
+import dan200.computercraft.core.asm.PeripheralMethod;
+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.capabilities.Capability;
+import net.minecraftforge.common.util.LazyOptional;
+import net.minecraftforge.energy.CapabilityEnergy;
+import net.minecraftforge.fluids.capability.CapabilityFluidHandler;
+import net.minecraftforge.items.CapabilityItemHandler;
+
+import javax.annotation.Nonnull;
+import java.util.ArrayList;
+import java.util.List;
+
+public class GenericPeripheralProvider
+{
+    private static final Capability<?>[] CAPABILITIES = new Capability<?>[] {
+        CapabilityItemHandler.ITEM_HANDLER_CAPABILITY,
+        CapabilityEnergy.ENERGY,
+        CapabilityFluidHandler.FLUID_HANDLER_CAPABILITY,
+    };
+
+    @Nonnull
+    public static LazyOptional<IPeripheral> getPeripheral( @Nonnull World world, @Nonnull BlockPos pos, @Nonnull Direction side )
+    {
+        if( !ComputerCraft.genericPeripheral ) return LazyOptional.empty();
+
+        TileEntity tile = world.getTileEntity( pos );
+        if( tile == null ) return LazyOptional.empty();
+
+        ArrayList<SaturatedMethod> saturated = new ArrayList<>( 0 );
+        LazyOptional<IPeripheral> peripheral = LazyOptional.of( () -> new GenericPeripheral( tile, saturated ) );
+
+        List<NamedMethod<PeripheralMethod>> tileMethods = PeripheralMethod.GENERATOR.getMethods( tile.getClass() );
+        if( !tileMethods.isEmpty() ) addSaturated( saturated, tile, tileMethods );
+
+        for( Capability<?> capability : CAPABILITIES )
+        {
+            LazyOptional<?> wrapper = tile.getCapability( capability );
+            wrapper.ifPresent( contents -> {
+                List<NamedMethod<PeripheralMethod>> capabilityMethods = PeripheralMethod.GENERATOR.getMethods( contents.getClass() );
+                if( capabilityMethods.isEmpty() ) return;
+
+                addSaturated( saturated, contents, capabilityMethods );
+                wrapper.addListener( x -> peripheral.invalidate() );
+            } );
+        }
+
+        return saturated.isEmpty() ? LazyOptional.empty() : peripheral;
+    }
+
+    private static void addSaturated( ArrayList<SaturatedMethod> saturated, Object target, List<NamedMethod<PeripheralMethod>> methods )
+    {
+        saturated.ensureCapacity( saturated.size() + methods.size() );
+        for( NamedMethod<PeripheralMethod> method : methods )
+        {
+            saturated.add( new SaturatedMethod( target, method ) );
+        }
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/SaturatedMethod.java

@@ -0,0 +1,59 @@
+/*
+ * 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.peripheral.generic;
+
+import dan200.computercraft.api.lua.IArguments;
+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.core.asm.NamedMethod;
+import dan200.computercraft.core.asm.PeripheralMethod;
+
+import javax.annotation.Nonnull;
+
+final class SaturatedMethod
+{
+    private final Object target;
+    private final String name;
+    private final PeripheralMethod method;
+
+    SaturatedMethod( Object target, NamedMethod<PeripheralMethod> method )
+    {
+        this.target = target;
+        this.name = method.getName();
+        this.method = method.getMethod();
+    }
+
+    @Nonnull
+    MethodResult apply( @Nonnull ILuaContext context, @Nonnull IComputerAccess computer, @Nonnull IArguments args ) throws LuaException
+    {
+        return method.apply( target, context, computer, args );
+    }
+
+    @Nonnull
+    String getName()
+    {
+        return name;
+    }
+
+    @Override
+    public boolean equals( Object obj )
+    {
+        if( obj == this ) return true;
+        if( !(obj instanceof SaturatedMethod) ) return false;
+
+        SaturatedMethod other = (SaturatedMethod) obj;
+        return method == other.method && target.equals( other.target );
+    }
+
+    @Override
+    public int hashCode()
+    {
+        return 31 * target.hashCode() + method.hashCode();
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/meta/FluidMeta.java

@@ -0,0 +1,24 @@
+/*
+ * 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.peripheral.generic.meta;
+
+import net.minecraftforge.fluids.FluidStack;
+
+import javax.annotation.Nonnull;
+import java.util.Map;
+import java.util.Objects;
+
+public class FluidMeta
+{
+    @Nonnull
+    public static <T extends Map<? super String, Object>> T fillBasicMeta( @Nonnull T data, @Nonnull FluidStack stack )
+    {
+        data.put( "name", Objects.toString( stack.getFluid().getRegistryName() ) );
+        data.put( "amount", stack.getAmount() );
+        return data;
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/meta/ItemMeta.java

@@ -0,0 +1,85 @@
+/*
+ * 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.peripheral.generic.meta;
+
+import com.google.gson.JsonParseException;
+import net.minecraft.item.ItemStack;
+import net.minecraft.nbt.CompoundNBT;
+import net.minecraft.nbt.INBT;
+import net.minecraft.nbt.ListNBT;
+import net.minecraft.util.text.ITextComponent;
+import net.minecraftforge.common.util.Constants;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+public class ItemMeta
+{
+    @Nonnull
+    public static <T extends Map<? super String, Object>> T fillBasicMeta( @Nonnull T data, @Nonnull ItemStack stack )
+    {
+        data.put( "name", Objects.toString( stack.getItem().getRegistryName() ) );
+        data.put( "count", stack.getCount() );
+        return data;
+    }
+
+    @Nonnull
+    public static <T extends Map<? super String, Object>> T fillMeta( @Nonnull T data, @Nonnull ItemStack stack )
+    {
+        if( stack.isEmpty() ) return data;
+
+        fillBasicMeta( data, stack );
+
+        data.put( "displayName", stack.getDisplayName().getString() );
+        data.put( "rawName", stack.getTranslationKey() );
+        data.put( "maxCount", stack.getMaxStackSize() );
+
+        if( stack.isDamageable() )
+        {
+            data.put( "damage", stack.getDamage() );
+            data.put( "maxDamage", stack.getMaxDamage() );
+        }
+
+        if( stack.getItem().showDurabilityBar( stack ) )
+        {
+            data.put( "durability", stack.getItem().getDurabilityForDisplay( stack ) );
+        }
+
+        CompoundNBT tag = stack.getTag();
+        if( tag != null && tag.contains( "display", Constants.NBT.TAG_COMPOUND ) )
+        {
+            CompoundNBT displayTag = tag.getCompound( "display" );
+            if( displayTag.contains( "Lore", Constants.NBT.TAG_LIST ) )
+            {
+                ListNBT loreTag = displayTag.getList( "Lore", Constants.NBT.TAG_STRING );
+                data.put( "lore", loreTag.stream()
+                    .map( ItemMeta::parseTextComponent )
+                    .filter( Objects::nonNull )
+                    .map( ITextComponent::getString )
+                    .collect( Collectors.toList() ) );
+            }
+        }
+
+        return data;
+    }
+
+    @Nullable
+    private static ITextComponent parseTextComponent( @Nonnull INBT x )
+    {
+        try
+        {
+            return ITextComponent.Serializer.fromJson( x.getString() );
+        }
+        catch( JsonParseException e )
+        {
+            return null;
+        }
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/methods/ArgumentHelpers.java

@@ -0,0 +1,66 @@
+/*
+ * 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.peripheral.generic.methods;
+
+import dan200.computercraft.api.lua.LuaException;
+import net.minecraft.util.ResourceLocation;
+import net.minecraft.util.ResourceLocationException;
+import net.minecraftforge.registries.IForgeRegistry;
+import net.minecraftforge.registries.IForgeRegistryEntry;
+
+import javax.annotation.Nonnull;
+
+/**
+ * A few helpers for working with arguments.
+ *
+ * This should really be moved into the public API. However, until I have settled on a suitable format, we'll keep it
+ * where it is used.
+ */
+final class ArgumentHelpers
+{
+    private ArgumentHelpers()
+    {
+    }
+
+    public static void assertBetween( double value, double min, double max, String message ) throws LuaException
+    {
+        if( value < min || value > max || Double.isNaN( value ) )
+        {
+            throw new LuaException( String.format( message, "between " + min + " and " + max ) );
+        }
+    }
+
+    public static void assertBetween( int value, int min, int max, String message ) throws LuaException
+    {
+        if( value < min || value > max )
+        {
+            throw new LuaException( String.format( message, "between " + min + " and " + max ) );
+        }
+    }
+
+    @Nonnull
+    public static <T extends IForgeRegistryEntry<T>> T getRegistryEntry( String name, String typeName, IForgeRegistry<T> registry ) throws LuaException
+    {
+        ResourceLocation id;
+        try
+        {
+            id = new ResourceLocation( name );
+        }
+        catch( ResourceLocationException e )
+        {
+            id = null;
+        }
+
+        T value;
+        if( id == null || !registry.containsKey( id ) || (value = registry.getValue( id )) == null )
+        {
+            throw new LuaException( String.format( "Unknown %s '%s'", typeName, name ) );
+        }
+
+        return value;
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/methods/EnergyMethods.java

@@ -0,0 +1,39 @@
+/*
+ * 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.peripheral.generic.methods;
+
+import com.google.auto.service.AutoService;
+import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.core.asm.GenericSource;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.energy.IEnergyStorage;
+import net.minecraftforge.versions.forge.ForgeVersion;
+
+import javax.annotation.Nonnull;
+
+@AutoService( GenericSource.class )
+public class EnergyMethods implements GenericSource
+{
+    @Nonnull
+    @Override
+    public ResourceLocation id()
+    {
+        return new ResourceLocation( ForgeVersion.MOD_ID, "energy" );
+    }
+
+    @LuaFunction( mainThread = true )
+    public static int getEnergy( IEnergyStorage energy )
+    {
+        return energy.getEnergyStored();
+    }
+
+    @LuaFunction( mainThread = true )
+    public static int getEnergyCapacity( IEnergyStorage energy )
+    {
+        return energy.getMaxEnergyStored();
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/methods/FluidMethods.java

@@ -0,0 +1,173 @@
+/*
+ * 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.peripheral.generic.methods;
+
+import com.google.auto.service.AutoService;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.api.peripheral.IComputerAccess;
+import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.core.asm.GenericSource;
+import dan200.computercraft.shared.peripheral.generic.meta.FluidMeta;
+import net.minecraft.fluid.Fluid;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.capabilities.ICapabilityProvider;
+import net.minecraftforge.common.util.LazyOptional;
+import net.minecraftforge.fluids.FluidStack;
+import net.minecraftforge.fluids.capability.CapabilityFluidHandler;
+import net.minecraftforge.fluids.capability.IFluidHandler;
+import net.minecraftforge.registries.ForgeRegistries;
+import net.minecraftforge.versions.forge.ForgeVersion;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+import static dan200.computercraft.shared.peripheral.generic.methods.ArgumentHelpers.getRegistryEntry;
+
+@AutoService( GenericSource.class )
+public class FluidMethods implements GenericSource
+{
+    @Nonnull
+    @Override
+    public ResourceLocation id()
+    {
+        return new ResourceLocation( ForgeVersion.MOD_ID, "fluid" );
+    }
+
+    @LuaFunction( mainThread = true )
+    public static Map<Integer, Map<String, ?>> tanks( IFluidHandler fluids )
+    {
+        Map<Integer, Map<String, ?>> result = new HashMap<>();
+        int size = fluids.getTanks();
+        for( int i = 0; i < size; i++ )
+        {
+            FluidStack stack = fluids.getFluidInTank( i );
+            if( !stack.isEmpty() ) result.put( i + 1, FluidMeta.fillBasicMeta( new HashMap<>( 4 ), stack ) );
+        }
+
+        return result;
+    }
+
+    @LuaFunction( mainThread = true )
+    public static int pushFluid(
+        IFluidHandler from, IComputerAccess computer,
+        String toName, Optional<Integer> limit, Optional<String> fluidName
+    ) throws LuaException
+    {
+        Fluid fluid = fluidName.isPresent()
+            ? getRegistryEntry( fluidName.get(), "fluid", ForgeRegistries.FLUIDS )
+            : null;
+
+        // Find location to transfer to
+        IPeripheral location = computer.getAvailablePeripheral( toName );
+        if( location == null ) throw new LuaException( "Target '" + toName + "' does not exist" );
+
+        IFluidHandler to = extractHandler( location.getTarget() );
+        if( to == null ) throw new LuaException( "Target '" + toName + "' is not an tank" );
+
+        int actualLimit = limit.orElse( Integer.MAX_VALUE );
+        if( actualLimit <= 0 ) throw new LuaException( "Limit must be > 0" );
+
+        return fluid == null
+            ? moveFluid( from, actualLimit, to )
+            : moveFluid( from, new FluidStack( fluid, actualLimit ), to );
+    }
+
+    @LuaFunction( mainThread = true )
+    public static int pullFluid(
+        IFluidHandler to, IComputerAccess computer,
+        String fromName, Optional<Integer> limit, Optional<String> fluidName
+    ) throws LuaException
+    {
+        Fluid fluid = fluidName.isPresent()
+            ? getRegistryEntry( fluidName.get(), "fluid", ForgeRegistries.FLUIDS )
+            : null;
+
+        // Find location to transfer to
+        IPeripheral location = computer.getAvailablePeripheral( fromName );
+        if( location == null ) throw new LuaException( "Target '" + fromName + "' does not exist" );
+
+        IFluidHandler from = extractHandler( location.getTarget() );
+        if( from == null ) throw new LuaException( "Target '" + fromName + "' is not an tank" );
+
+        int actualLimit = limit.orElse( Integer.MAX_VALUE );
+        if( actualLimit <= 0 ) throw new LuaException( "Limit must be > 0" );
+
+        return fluid == null
+            ? moveFluid( from, actualLimit, to )
+            : moveFluid( from, new FluidStack( fluid, actualLimit ), to );
+    }
+
+    @Nullable
+    private static IFluidHandler extractHandler( @Nullable Object object )
+    {
+        if( object instanceof ICapabilityProvider )
+        {
+            LazyOptional<IFluidHandler> cap = ((ICapabilityProvider) object).getCapability( CapabilityFluidHandler.FLUID_HANDLER_CAPABILITY );
+            if( cap.isPresent() ) return cap.orElseThrow( NullPointerException::new );
+        }
+
+        if( object instanceof IFluidHandler ) return (IFluidHandler) object;
+        return null;
+    }
+
+    /**
+     * Move fluid from one handler to another.
+     *
+     * @param from  The handler to move from.
+     * @param limit The maximum amount of fluid to move.
+     * @param to    The handler to move to.
+     * @return The amount of fluid moved.
+     */
+    private static int moveFluid( IFluidHandler from, int limit, IFluidHandler to )
+    {
+        return moveFluid( from, from.drain( limit, IFluidHandler.FluidAction.SIMULATE ), limit, to );
+    }
+
+    /**
+     * Move fluid from one handler to another.
+     *
+     * @param from  The handler to move from.
+     * @param fluid The fluid and limit to move.
+     * @param to    The handler to move to.
+     * @return The amount of fluid moved.
+     */
+    private static int moveFluid( IFluidHandler from, FluidStack fluid, IFluidHandler to )
+    {
+        return moveFluid( from, from.drain( fluid, IFluidHandler.FluidAction.SIMULATE ), fluid.getAmount(), to );
+    }
+
+    /**
+     * Move fluid from one handler to another.
+     *
+     * @param from      The handler to move from.
+     * @param extracted The fluid which is extracted from {@code from}.
+     * @param limit     The maximum amount of fluid to move.
+     * @param to        The handler to move to.
+     * @return The amount of fluid moved.
+     */
+    private static int moveFluid( IFluidHandler from, FluidStack extracted, int limit, IFluidHandler to )
+    {
+        if( extracted == null || extracted.getAmount() <= 0 ) return 0;
+
+        // Limit the amount to extract.
+        extracted = extracted.copy();
+        extracted.setAmount( Math.min( extracted.getAmount(), limit ) );
+
+        int inserted = to.fill( extracted.copy(), IFluidHandler.FluidAction.EXECUTE );
+        if( inserted <= 0 ) return 0;
+
+        // Remove the item from the original inventory. Technically this could fail, but there's little we can do
+        // about that.
+        extracted.setAmount( inserted );
+        from.drain( extracted, IFluidHandler.FluidAction.EXECUTE );
+        return inserted;
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/generic/methods/InventoryMethods.java

@@ -0,0 +1,161 @@
+/*
+ * 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.peripheral.generic.methods;
+
+import com.google.auto.service.AutoService;
+import dan200.computercraft.api.lua.LuaException;
+import dan200.computercraft.api.lua.LuaFunction;
+import dan200.computercraft.api.peripheral.IComputerAccess;
+import dan200.computercraft.api.peripheral.IPeripheral;
+import dan200.computercraft.core.asm.GenericSource;
+import dan200.computercraft.shared.peripheral.generic.meta.ItemMeta;
+import net.minecraft.inventory.IInventory;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.ResourceLocation;
+import net.minecraftforge.common.capabilities.ICapabilityProvider;
+import net.minecraftforge.common.util.LazyOptional;
+import net.minecraftforge.items.CapabilityItemHandler;
+import net.minecraftforge.items.IItemHandler;
+import net.minecraftforge.items.ItemHandlerHelper;
+import net.minecraftforge.items.wrapper.InvWrapper;
+import net.minecraftforge.versions.forge.ForgeVersion;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+
+import static dan200.computercraft.shared.peripheral.generic.methods.ArgumentHelpers.assertBetween;
+
+@AutoService( GenericSource.class )
+public class InventoryMethods implements GenericSource
+{
+    @Nonnull
+    @Override
+    public ResourceLocation id()
+    {
+        return new ResourceLocation( ForgeVersion.MOD_ID, "inventory" );
+    }
+
+    @LuaFunction( mainThread = true )
+    public static int size( IItemHandler inventory )
+    {
+        return inventory.getSlots();
+    }
+
+    @LuaFunction( mainThread = true )
+    public static Map<Integer, Map<String, ?>> list( IItemHandler inventory )
+    {
+        Map<Integer, Map<String, ?>> result = new HashMap<>();
+        int size = inventory.getSlots();
+        for( int i = 0; i < size; i++ )
+        {
+            ItemStack stack = inventory.getStackInSlot( i );
+            if( !stack.isEmpty() ) result.put( i + 1, ItemMeta.fillBasicMeta( new HashMap<>( 4 ), stack ) );
+        }
+
+        return result;
+    }
+
+    @LuaFunction( mainThread = true )
+    public static Map<String, ?> getItemMeta( IItemHandler inventory, int slot ) throws LuaException
+    {
+        assertBetween( slot, 1, inventory.getSlots(), "Slot out of range (%s)" );
+
+        ItemStack stack = inventory.getStackInSlot( slot - 1 );
+        return stack.isEmpty() ? null : ItemMeta.fillMeta( new HashMap<>(), stack );
+    }
+
+    @LuaFunction( mainThread = true )
+    public static int pushItems(
+        IItemHandler from, IComputerAccess computer,
+        String toName, int fromSlot, Optional<Integer> limit, Optional<Integer> toSlot
+    ) throws LuaException
+    {
+        // Find location to transfer to
+        IPeripheral location = computer.getAvailablePeripheral( toName );
+        if( location == null ) throw new LuaException( "Target '" + toName + "' does not exist" );
+
+        IItemHandler to = extractHandler( location.getTarget() );
+        if( to == null ) throw new LuaException( "Target '" + toName + "' is not an inventory" );
+
+        // Validate slots
+        int actualLimit = limit.orElse( Integer.MAX_VALUE );
+        if( actualLimit <= 0 ) throw new LuaException( "Limit must be > 0" );
+        assertBetween( fromSlot, 1, from.getSlots(), "From slot out of range (%s)" );
+        if( toSlot.isPresent() ) assertBetween( toSlot.get(), 1, to.getSlots(), "To slot out of range (%s)" );
+
+        return moveItem( from, fromSlot - 1, to, toSlot.orElse( 0 ) - 1, actualLimit );
+    }
+
+    @LuaFunction( mainThread = true )
+    public static int pullItems(
+        IItemHandler to, IComputerAccess computer,
+        String fromName, int fromSlot, Optional<Integer> limit, Optional<Integer> toSlot
+    ) throws LuaException
+    {
+        // Find location to transfer to
+        IPeripheral location = computer.getAvailablePeripheral( fromName );
+        if( location == null ) throw new LuaException( "Source '" + fromName + "' does not exist" );
+
+        IItemHandler from = extractHandler( location.getTarget() );
+        if( from == null ) throw new LuaException( "Source '" + fromName + "' is not an inventory" );
+
+        // Validate slots
+        int actualLimit = limit.orElse( Integer.MAX_VALUE );
+        if( actualLimit <= 0 ) throw new LuaException( "Limit must be > 0" );
+        assertBetween( fromSlot, 1, from.getSlots(), "From slot out of range (%s)" );
+        if( toSlot.isPresent() ) assertBetween( toSlot.get(), 1, to.getSlots(), "To slot out of range (%s)" );
+
+        return moveItem( from, fromSlot - 1, to, toSlot.orElse( 0 ) - 1, actualLimit );
+    }
+
+    @Nullable
+    private static IItemHandler extractHandler( @Nullable Object object )
+    {
+        if( object instanceof ICapabilityProvider )
+        {
+            LazyOptional<IItemHandler> cap = ((ICapabilityProvider) object).getCapability( CapabilityItemHandler.ITEM_HANDLER_CAPABILITY );
+            if( cap.isPresent() ) return cap.orElseThrow( NullPointerException::new );
+        }
+
+        if( object instanceof IItemHandler ) return (IItemHandler) object;
+        if( object instanceof IInventory ) return new InvWrapper( (IInventory) object );
+        return null;
+    }
+
+    /**
+     * Move an item from one handler to another.
+     *
+     * @param from     The handler to move from.
+     * @param fromSlot The slot to move from.
+     * @param to       The handler to move to.
+     * @param toSlot   The slot to move to. Use any number < 0 to represent any slot.
+     * @param limit    The max number to move. {@link Integer#MAX_VALUE} for no limit.
+     * @return The number of items moved.
+     */
+    private static int moveItem( IItemHandler from, int fromSlot, IItemHandler to, int toSlot, final int limit )
+    {
+        // See how much we can get out of this slot
+        ItemStack extracted = from.extractItem( fromSlot, limit, true );
+        if( extracted.isEmpty() ) return 0;
+
+        // Limit the amount to extract
+        int extractCount = Math.min( extracted.getCount(), limit );
+        extracted.setCount( extractCount );
+
+        ItemStack remainder = toSlot < 0 ? ItemHandlerHelper.insertItem( to, extracted, false ) : to.insertItem( toSlot, extracted, false );
+        int inserted = remainder.isEmpty() ? extractCount : extractCount - remainder.getCount();
+        if( inserted <= 0 ) return 0;
+
+        // Remove the item from the original inventory. Technically this could fail, but there's little we can do
+        // about that.
+        from.extractItem( fromSlot, inserted, false );
+        return inserted;
+    }
+}