ASContainer.java

package org.unh0lytigg.core.annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@interface ASContainer {
	public AutoSubscribe[] value();
}

AutoSubscribe.java

package org.unh0lytigg.core.annotations;

import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Repeatable(ASContainer.class)
public @interface AutoSubscribe {
	public Bus busToAttach() default Bus.AUTO;
	public String customBusName() default "";
	public AttachPhase phase() default AttachPhase.POST_INIT;
	public int numAutoAttach() default 1;
	
	public static enum Bus {
		AUTO,
		FML,
		FORGE,
		TERRAIN_GEN,
		ORE_GEN,
		CUSTOM;
	}
	
	public static enum AttachPhase {
		PRE_INIT,
		INIT,
		POST_INIT;
	}
}

AutoSubscribeWorker.java

package org.unh0lytigg.core.background;

import static org.unh0lytigg.core.TiggCore.LOGGER;
import static org.unh0lytigg.core.asm.ASMInfo.table;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

import net.minecraftforge.fml.common.discovery.ASMDataTable.ASMData;
import net.minecraftforge.fml.common.eventhandler.Event;
import net.minecraftforge.fml.common.eventhandler.EventBus;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;

import org.unh0lytigg.core.EventBusAccess;
import org.unh0lytigg.core.annotations.AutoSubscribe;
import org.unh0lytigg.core.annotations.AutoSubscribe.AttachPhase;
import org.unh0lytigg.core.annotations.AutoSubscribe.Bus;
import org.unh0lytigg.core.events.EventBusMap;

import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;

public class AutoSubscribeWorker {
	private static Set<ASMData> data;
	public static void prePhase() {
		data = Sets.newHashSet();
		data.addAll(table.getAll("org.unh0lytigg.core.annotations.AutoSubscribe"));
		data.addAll(table.getAll("org.unh0lytigg.core.annotations.ASContainer"));
		data = data.stream().filter(d -> { return d.getObjectName() != null; }).collect(Collectors.toSet());
		try {
			doWork(AttachPhase.PRE_INIT);
		} catch (Exception e) {
			Throwables.propagate(e);
		}
	}
	
	public static void initPhase() {
		try {
			doWork(AttachPhase.INIT);
		} catch (Exception e) {
			Throwables.propagate(e);
		}
	}
	
	public static void postPhase() {
		try {
			doWork(AttachPhase.POST_INIT);
		} catch (Exception e) {
			Throwables.propagate(e);
		}
	}
	
	private static void doWork(AttachPhase phase) throws Exception {
		for (ASMData d : data) {
			if (d.getObjectName() == null) {
				continue;
			}
			Class<?> c = Class.forName(d.getClassName());
			Field f = c.getDeclaredField(d.getObjectName());
			if ((f.getModifiers() & Modifier.STATIC) != Modifier.STATIC)
				continue;
			f.setAccessible(true);
			Object value = f.get(null);
			AutoSubscribe[] infos = f.getAnnotationsByType(AutoSubscribe.class);
			infoloop:
			for (AutoSubscribe info : infos) {
				if (info.phase() != phase)
					continue;
				Bus b = info.busToAttach();
				EventBus bus = null;
				switch(b) {
				case FML:
					bus = EventBusAccess.fml();
					break;
				case FORGE:
					bus = EventBusAccess.forge();
					break;
				case TERRAIN_GEN:
					bus = EventBusAccess.terrain();
					break;
				case ORE_GEN:
					bus = EventBusAccess.ore();
					break;
				case CUSTOM:
					bus = EventBusAccess.custom(info.customBusName());
					break;
				case AUTO: 
					autoRegister(value, info, c);
					break infoloop;
				default:
					break;
				}
				if (bus != null)
					bus.register(value);
			}
		}
	}
	
	@SuppressWarnings("unchecked")
	private static void autoRegister(Object value, AutoSubscribe info, Class<?> clazz) {
		List<EventBus> busses = Lists.newArrayList();
		for (Method m : clazz.getDeclaredMethods()) {
			if (m.isAnnotationPresent(SubscribeEvent.class)) {
				if (m.getParameterTypes().length == 1 && (Event.class.isAssignableFrom(m.getParameterTypes()[0]))) {
					Class<? extends Event> c = (Class<? extends Event>) m.getParameterTypes()[0]; // Should be safe, check is being done in if statement
					EventBus b = EventBusMap.getBus(c);
					if (b != null && !busses.contains(b))
						busses.add(b);
				}
			}
		}
		if (busses.size() != info.numAutoAttach())
			LOGGER.warn("AutoSubscribeWorker.autoRegister: expected " + info.numAutoAttach() + " busses for " + clazz.getTypeName() + ", got " + busses.size());
		for (EventBus b : busses)
			b.register(value);
	}
}