Squake/java/squeek/quakemovement/ASMPlugin.java

package squeek.quakemovement;

import net.minecraft.launchwrapper.IClassTransformer;
import net.minecraftforge.fml.relauncher.IFMLLoadingPlugin;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.*;

import java.util.Map;

@IFMLLoadingPlugin.MCVersion("1.12")
public class ASMPlugin implements IFMLLoadingPlugin, IClassTransformer
{
	public static boolean isObfuscated = false;
	private static String CLASS_ENTITY_PLAYER = "net.minecraft.entity.player.EntityPlayer";
	private static String CLASS_ENTITY = "net.minecraft.entity.Entity";
	private static String CLASS_QUAKE_CLIENT_PLAYER = "squeek.quakemovement.QuakeClientPlayer";
	private static String CLASS_QUAKE_SERVER_PLAYER = "squeek.quakemovement.QuakeServerPlayer";

	@Override
	public byte[] transform(String name, String transformedName, byte[] bytes)
	{
		if (transformedName.equals(CLASS_ENTITY_PLAYER))
		{
			ClassNode classNode = readClassFromBytes(bytes);
			MethodNode method;

			method = findMethodNodeOfClass(classNode, isObfuscated ? "a" : "travel", "(FFF)V");
			if (method == null)
				throw new RuntimeException("could not find EntityPlayer.travel");

			InsnList loadParameters = new InsnList();
			loadParameters.add(new VarInsnNode(Opcodes.ALOAD, 0));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 1));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 2));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 3));
			injectStandardHook(method, findFirstInstruction(method), CLASS_QUAKE_CLIENT_PLAYER, "moveEntityWithHeading", toMethodDescriptor("Z", CLASS_ENTITY_PLAYER, "F", "F", "F"), loadParameters);

			method = findMethodNodeOfClass(classNode, isObfuscated ? "n" : "onLivingUpdate", "()V");
			if (method == null)
				throw new RuntimeException("could not find EntityPlayer.onLivingUpdate");

			loadParameters.clear();
			loadParameters.add(new VarInsnNode(Opcodes.ALOAD, 0));
			injectSimpleHook(method, findFirstInstruction(method), CLASS_QUAKE_CLIENT_PLAYER, "beforeOnLivingUpdate", toMethodDescriptor("V", CLASS_ENTITY_PLAYER), loadParameters);

			method = findMethodNodeOfClass(classNode, isObfuscated ? "cm" : "jump", "()V");
			if (method == null)
				throw new RuntimeException("could not find EntityPlayer.jump");

			loadParameters.clear();
			loadParameters.add(new VarInsnNode(Opcodes.ALOAD, 0));
			injectSimpleHook(method, findLastInstructionWithOpcode(method, Opcodes.RETURN), CLASS_QUAKE_CLIENT_PLAYER, "afterJump", toMethodDescriptor("V", CLASS_ENTITY_PLAYER), loadParameters);

			method = findMethodNodeOfClass(classNode, isObfuscated ? "e" : "fall", "(FF)V");
			if (method == null)
				throw new RuntimeException("could not find EntityPlayer.fall");

			loadParameters.clear();
			loadParameters.add(new VarInsnNode(Opcodes.ALOAD, 0));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 1));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 1));
			injectSimpleHook(method, findFirstInstruction(method), CLASS_QUAKE_SERVER_PLAYER, "beforeFall", toMethodDescriptor("V", CLASS_ENTITY_PLAYER, "F", "F"), loadParameters);

			loadParameters.clear();
			loadParameters.add(new VarInsnNode(Opcodes.ALOAD, 0));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 1));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 1));
			injectSimpleHook(method, findLastInstructionWithOpcode(method, Opcodes.RETURN), CLASS_QUAKE_SERVER_PLAYER, "afterFall", toMethodDescriptor("V", CLASS_ENTITY_PLAYER, "F", "F"), loadParameters);

			return writeClassToBytes(classNode);
		}
		else if (transformedName.equals(CLASS_ENTITY))
		{
			ClassNode classNode = readClassFromBytes(bytes);
			MethodNode method;

			method = findMethodNodeOfClass(classNode, isObfuscated ? "b" : "moveRelative", "(FFFF)V");
			if (method == null)
				throw new RuntimeException("could not find Entity.moveRelative");

			InsnList loadParameters = new InsnList();
			loadParameters.add(new VarInsnNode(Opcodes.ALOAD, 0));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 1));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 2));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 3));
			loadParameters.add(new VarInsnNode(Opcodes.FLOAD, 4));
			injectStandardHook(method, findFirstInstruction(method), CLASS_QUAKE_CLIENT_PLAYER, "moveRelativeBase", toMethodDescriptor("Z", CLASS_ENTITY, "F", "F", "F", "F"), loadParameters);

			return writeClassToBytes(classNode);
		}
		return bytes;
	}

	private void injectStandardHook(MethodNode method, AbstractInsnNode node, String hookClassName, String hookMethodName, String hookMethodDescriptor, InsnList loadParameters)
	{
		InsnList toInject = new InsnList();
		LabelNode ifNotCanceled = new LabelNode();
		toInject.add(loadParameters);
		toInject.add(new MethodInsnNode(Opcodes.INVOKESTATIC, toInternalClassName(hookClassName), hookMethodName, hookMethodDescriptor, false));
		toInject.add(new JumpInsnNode(Opcodes.IFEQ, ifNotCanceled));
		toInject.add(new InsnNode(Opcodes.RETURN));
		toInject.add(ifNotCanceled);

		method.instructions.insertBefore(node, toInject);
	}

	private void injectSimpleHook(MethodNode method, AbstractInsnNode node, String hookClassName, String hookMethodName, String hookMethodDescriptor, InsnList loadParameters)
	{
		InsnList toInject = new InsnList();
		toInject.add(loadParameters);
		toInject.add(new MethodInsnNode(Opcodes.INVOKESTATIC, toInternalClassName(hookClassName), hookMethodName, hookMethodDescriptor, false));

		method.instructions.insertBefore(node, toInject);
	}

	@Override
	public String[] getASMTransformerClass()
	{
		return new String[]{this.getClass().getName()};
	}

	@Override
	public String getModContainerClass()
	{
		return null;
	}

	@Override
	public String getSetupClass()
	{
		return null;
	}

	@Override
	public void injectData(Map<String, Object> data)
	{
		isObfuscated = (Boolean) data.get("runtimeDeobfuscationEnabled");
	}

	@Override
	public String getAccessTransformerClass()
	{
		return null;
	}

	private ClassNode readClassFromBytes(byte[] bytes)
	{
		ClassNode classNode = new ClassNode();
		ClassReader classReader = new ClassReader(bytes);
		classReader.accept(classNode, 0);
		return classNode;
	}

	private byte[] writeClassToBytes(ClassNode classNode)
	{
		ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS | ClassWriter.COMPUTE_FRAMES);
		classNode.accept(writer);
		return writer.toByteArray();
	}

	private MethodNode findMethodNodeOfClass(ClassNode classNode, String methodName, String methodDesc)
	{
		for (MethodNode method : classNode.methods)
		{
			if (method.name.equals(methodName) && method.desc.equals(methodDesc))
			{
				return method;
			}
		}
		return null;
	}

	private static String toInternalClassName(String className)
	{
		return className.replace('.', '/');
	}

	private static boolean isDescriptor(String descriptor)
	{
		return descriptor.length() == 1 || (descriptor.startsWith("L") && descriptor.endsWith(";"));
	}

	private static String toDescriptor(String className)
	{
		return isDescriptor(className) ? className : "L" + toInternalClassName(className) + ";";
	}

	private static String toMethodDescriptor(String returnType, String... paramTypes)
	{
		StringBuilder paramDescriptors = new StringBuilder();
		for (String paramType : paramTypes)
			paramDescriptors.append(toDescriptor(paramType));

		return "(" + paramDescriptors.toString() + ")" + toDescriptor(returnType);
	}

	private static boolean isLabelOrLineNumber(AbstractInsnNode insn)
	{
		return insn.getType() == AbstractInsnNode.LABEL || insn.getType() == AbstractInsnNode.LINE;
	}

	private static AbstractInsnNode getOrFindInstruction(AbstractInsnNode firstInsnToCheck, boolean reverseDirection)
	{
		for (AbstractInsnNode instruction = firstInsnToCheck; instruction != null; instruction = reverseDirection ? instruction.getPrevious() : instruction.getNext())
		{
			if (!isLabelOrLineNumber(instruction))
				return instruction;
		}
		return null;
	}

	private static AbstractInsnNode findFirstInstruction(MethodNode method)
	{
		return getOrFindInstruction(method.instructions.getFirst(), false);
	}

	public static AbstractInsnNode getOrFindInstructionWithOpcode(AbstractInsnNode firstInsnToCheck, int opcode, boolean reverseDirection)
	{
		for (AbstractInsnNode instruction = firstInsnToCheck; instruction != null; instruction = reverseDirection ? instruction.getPrevious() : instruction.getNext())
		{
			if (instruction.getOpcode() == opcode)
				return instruction;
		}
		return null;
	}

	public static AbstractInsnNode findLastInstructionWithOpcode(MethodNode method, int opcode)
	{
		return getOrFindInstructionWithOpcode(method.instructions.getLast(), opcode, true);
	}
}