4 files changed, 232 insertions, 8 deletions
diff --git a/src/main/java/bscv/asm/BoSCoVicinoLoader.java b/src/main/java/bscv/asm/BoSCoVicinoLoader.java
index a41e883..77d5f6e 100644
--- a/src/main/java/bscv/asm/BoSCoVicinoLoader.java
+++ b/src/main/java/bscv/asm/BoSCoVicinoLoader.java
@@ -1,32 +1,189 @@
 package bscv.asm;
 
-import java.io.File;
 import java.io.IOException;
-import java.util.EnumSet;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.*;
+import java.util.stream.Collectors;
 
+import bscv.asm.api.AnnotationChecker;
+import bscv.asm.api.annotations.Inject;
+import bscv.asm.api.annotations.Patch;
+import com.google.common.collect.HashMultimap;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.Type;
 
 import cpw.mods.modlauncher.serviceapi.ILaunchPluginService;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.MethodNode;
 
 public class BoSCoVicinoLoader implements ILaunchPluginService {
 
-	public static Logger LOGGER = LogManager.getLogger("BSCV-ASM");
+	public static final String NAME = "boscovicino_asm"; //temp name
+	public static final Logger LOGGER = LogManager.getLogger("BoSCoVicinoASM");
+
+	private static final EnumSet<Phase> YAY = EnumSet.of(Phase.BEFORE);
+	private static final EnumSet<Phase> NAY = EnumSet.noneOf(Phase.class);
+
+	private static final HashMultimap<String, Class<?>> patchClasses = HashMultimap.create();
 
 	public BoSCoVicinoLoader() {
-		LOGGER.info("BoSCoVicinoLoader instantiation");
+		LOGGER.info("BoSCoVicinoLoader instantiated successfully!");
 	}
 
 	@Override
 	public String name() {
-		return "boscovicino_asm";
+		return NAME;
+	}
+
+	@Override
+	public EnumSet<Phase> handlesClass(Type classType, final boolean isEmpty) {
+		//if(!isEmpty && shouldHandle(classType))
+		//	LOGGER.info("CLAZZ >>> {}", classType.getClassName());
+		//return NAY;
+		throw new IllegalStateException("Outdated ModLauncher"); //mixin does it
 	}
 
 	@Override
-	public EnumSet<ILaunchPluginService.Phase> handlesClass(Type classType, final boolean isEmpty) {
-		LOGGER.info(String.format("CLAZZ >>> %s", classType.getClassName()));
-		return EnumSet.noneOf(Phase.class);
+	public EnumSet<Phase> handlesClass(Type classType, final boolean isEmpty, final String reason) {
+		if(isEmpty) return NAY;
+		String name = classType.getClassName();
+		if(name.startsWith("net.minecraft.") || name.indexOf('.') == -1)
+			return YAY;
+		else {
+			try {
+				if(hasAnnotation(name)) {
+					Class<?> patch = Class.forName(name);
+					patchClasses.put(Type.getDescriptor(patch.getAnnotation(Patch.class).value()), patch);
+					return YAY;
+				}
+			} catch(IOException | ClassNotFoundException e) {
+				LOGGER.debug("Could not load {}", name);
+			}
+			return NAY;
+		}
+	}
+
+	@Override
+	public int processClassWithFlags(Phase phase, ClassNode classNode, Type classType, String reason) {
+		if(patchClasses.containsKey(classType.getDescriptor())) {
+			//can have multiple patches working on same class
+			//each of these classes may attempt to patch a method one or more times
+			Set<String> classMethodNames = classNode.methods
+				.stream()
+				.map(m -> m.name)
+				.collect(Collectors.toSet());
+			Set<String> classMethodDescriptors = classNode.methods
+				.stream()
+				.map(m -> m.desc)
+				.collect(Collectors.toSet());
+			Set<Class<?>> relevantPatches = patchClasses.get(classType.getDescriptor());
+			HashMultimap<Object, Method> patches = HashMultimap.create();
+			relevantPatches
+				.forEach(p -> {
+					Set<Method> injectors =
+						getInjectorsInPatch(p)
+							.stream()
+							.filter(m -> {
+								Inject a = m.getAnnotation(Inject.class);
+								return
+									classMethodNames.contains(a.methodName())
+										&& classMethodDescriptors.contains(descriptorBuilder(a.returnType(), a.parameters()));
+							})
+							.collect(Collectors.toSet());
+					if(!injectors.isEmpty()) {
+						try {
+							patches.putAll(p.newInstance(), injectors);
+						} catch(InstantiationException | IllegalAccessException e) {
+							throw new RuntimeException(e); //todo: better catch
+						}
+					}
+				});
+			if(patches.isEmpty())
+				return ComputeFlags.NO_REWRITE;
+			else {
+				boolean success = false;
+				for(Object p : patches.keys())
+					for(Method m : patches.get(p))
+						success = success || processInjector(classNode, p, m);
+				return success ? ComputeFlags.COMPUTE_FRAMES : ComputeFlags.NO_REWRITE; //todo: is this the right flag?
+			}
+		} else return ComputeFlags.NO_REWRITE;
+	}
+
+	private boolean hasAnnotation(String name) throws IOException {
+		ClassReader cr = new ClassReader(name);
+		AnnotationChecker ac = new AnnotationChecker(Patch.class);
+		cr.accept(ac, 0);
+		return ac.isAnnotationPresent();
+	}
+
+	private Set<Method> getInjectorsInPatch(Class<?> patch) {
+		return Arrays.stream(patch.getDeclaredMethods())
+				.filter(m -> m.isAnnotationPresent(Inject.class))
+				.collect(Collectors.toSet());
+	}
+
+	public static String descriptorBuilder(Class<?> returnType, Class<?>[] parameters) {
+		StringBuilder desc = new StringBuilder("(");
+		for(Class<?> p : parameters)
+			desc.append(Type.getDescriptor(p));
+		desc.append(")");
+		desc.append(Type.getDescriptor(returnType));
+		return desc.toString();
+	}
+
+	private boolean processInjector(ClassNode target, Object patch, Method injector) {
+		//get relevant method from target
+		Optional<MethodNode> targetMethod =
+			target.methods
+				.stream()
+				.filter(m -> {
+					Inject a = injector.getAnnotation(Inject.class);
+					return m.name.equals(a.methodName()) && m.desc.equals(descriptorBuilder(a.returnType(), a.parameters()));
+				})
+				.findAny(); //there can literally only be one so this is safe and more efficient than findFirst
+
+		try {
+			if(!targetMethod.isPresent())
+				throw new NoSuchMethodException();
+			injector.invoke(patch, targetMethod.get());
+
+			LOGGER.info(
+				"Completed transformation task {} for {}::{}",
+				injector.getAnnotation(Inject.class).description(),
+				target.name,
+				targetMethod.get().name
+			);
+
+			return true;
+
+		} catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
+			if (e instanceof NoSuchMethodException) {
+				LOGGER.error(
+					"{} while attempting to find method {}::{} in task {}. This should never happen.",
+					e,
+					target.name,
+					injector.getAnnotation(Inject.class).methodName(),
+					injector.getAnnotation(Inject.class).description()
+				);
+			} else {
+				Throwable cause;
+				if(e instanceof InvocationTargetException)
+					cause = e.getCause();
+				else cause = e;
+				LOGGER.error(
+					"{} thrown from {}::{} for task with description {}",
+					cause,
+					target.name,
+					targetMethod.get().name,
+					injector.getAnnotation(Inject.class).description()
+				);
+			}
+			return false;
+		}
 	}
 }
 
diff --git a/src/main/java/bscv/asm/api/AnnotationChecker.java b/src/main/java/bscv/asm/api/AnnotationChecker.java
new file mode 100644
index 0000000..a0abbda
--- /dev/null
+++ b/src/main/java/bscv/asm/api/AnnotationChecker.java
@@ -0,0 +1,37 @@
+package bscv.asm.api;
+
+import org.objectweb.asm.AnnotationVisitor;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.Type;
+
+import java.lang.annotation.Annotation;
+
+/**
+ * ClassVisitor which checks whether a Class is annotated with
+ * a specific Annotation.
+ * @author Fraaz
+ */
+public class AnnotationChecker extends ClassVisitor {
+	private boolean annotationPresent;
+	private final String annotationDesc;
+
+	public AnnotationChecker(Class<? extends Annotation> a) {
+		super(Opcodes.ASM8); //hopefully lol
+		this.annotationPresent = false;
+		this.annotationDesc = Type.getDescriptor(a);
+	}
+
+	@Override
+	public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
+		if (visible && desc.equals(this.annotationDesc))
+			this.annotationPresent = true;
+		return super.visitAnnotation(desc, visible);
+		//returning null would delete our annotation, but we don't want that
+		//so we jut delegate to superclass
+	}
+
+	public boolean isAnnotationPresent() {
+		return this.annotationPresent;
+	}
+}
diff --git a/src/main/java/bscv/asm/api/annotations/Inject.java b/src/main/java/bscv/asm/api/annotations/Inject.java
new file mode 100644
index 0000000..dcf5fcb
--- /dev/null
+++ b/src/main/java/bscv/asm/api/annotations/Inject.java
@@ -0,0 +1,18 @@
+package bscv.asm.api.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target({ElementType.METHOD})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Inject {
+	String methodName();
+
+	Class<?> returnType();
+
+	Class<?>[] parameters();
+
+	String description() default "No description given";
+}
diff --git a/src/main/java/bscv/asm/api/annotations/Patch.java b/src/main/java/bscv/asm/api/annotations/Patch.java
new file mode 100644
index 0000000..4685845
--- /dev/null
+++ b/src/main/java/bscv/asm/api/annotations/Patch.java
@@ -0,0 +1,12 @@
+package bscv.asm.api.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Patch {
+	Class<?> value();
+}