HandlerListInjector.java

package lilypad.bukkit.connect.injector;

import java.util.ArrayList;
import java.util.EnumMap;
import java.util.List;

import lilypad.bukkit.connect.util.ReflectionUtils;

import org.bukkit.event.Event;
import org.bukkit.event.EventPriority;
import org.bukkit.event.HandlerList;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.RegisteredListener;

public class HandlerListInjector extends HandlerList {

	@SuppressWarnings("unchecked")
	public static void prioritize(Plugin plugin, Class<? extends Event> event) throws Exception {
		HandlerList handlerList = ReflectionUtils.getPrivateField(event, null, HandlerList.class, "handlers");
		HandlerListInjector injector = new HandlerListInjector(plugin);
		// move the handlerslots
		EnumMap<EventPriority, ArrayList<RegisteredListener>> handlerListHandlerSlots = ReflectionUtils.getPrivateField(HandlerList.class, handlerList, EnumMap.class, "handlerslots");
		EnumMap<EventPriority, ArrayList<RegisteredListener>> injectorHandlerSlots = ReflectionUtils.getPrivateField(HandlerList.class, injector, EnumMap.class, "handlerslots");
		injectorHandlerSlots.putAll(handlerListHandlerSlots);
		// remove old from allLists
		ArrayList<HandlerList> allLists = ReflectionUtils.getPrivateField(HandlerList.class, null, ArrayList.class, "allLists");
		allLists.remove(handlerList);
		// replace event handlers
		ReflectionUtils.setFinalField(event, null, "handlers", injector);
	}
	
	private Plugin plugin;
	private List<RegisteredListener> startListeners = new ArrayList<RegisteredListener>();
	private List<RegisteredListener> middleListeners = new ArrayList<RegisteredListener>();
	private List<RegisteredListener> endListeners = new ArrayList<RegisteredListener>();
	
	private HandlerListInjector(Plugin plugin) {
		this.plugin = plugin;
	}
	
	@Override
	public synchronized void bake() {
		super.bake();
		RegisteredListener[] handlers = super.getRegisteredListeners();
		// TODO we can speed this up greatly using arrays. It's not really necessary though, as this isn't a hot function
		for(RegisteredListener handler : handlers) {
			if(handler.getPlugin().equals(plugin)) {
				if(handler.getPriority().equals(EventPriority.LOWEST)) {
					this.startListeners.add(handler);
					continue;
				} else if(handler.getPriority().equals(EventPriority.MONITOR)) {
					this.endListeners.add(handler);
					continue;
				}
			}
			this.middleListeners.add(handler);
		}
		List<RegisteredListener> handlerList = new ArrayList<RegisteredListener>(handlers.length);
		handlerList.addAll(this.startListeners);
		handlerList.addAll(this.middleListeners);
		handlerList.addAll(this.endListeners);
		handlerList.toArray(handlers);
	}
	
}