/*
 * MessageHandlerManager.java
 * Copyright James Dempsey, 2014
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Created on 16/02/2014 9:19:23 am
 *
 * $Id$
 */
package pcgen.pluginmgr;

import javax.swing.event.EventListenerList;

import pcgen.pluginmgr.messages.ComponentAddedMessage;
import pcgen.pluginmgr.messages.ComponentRemovedMessage;

/**
 * The Class {@code MessageHandlerManager} records the list of message handlers
 * and ensures that they get advised of any messages in order. 
 *
 * <br>
 * 
 * @author James Dempsey <jdempsey@users.sourceforge.net>
 */

public class MessageHandlerManager
{
	private final PCGenMessageHandler postbox;
	private final EventListenerList chain;
	
	public MessageHandlerManager()
	{
		chain = new EventListenerList();
		postbox = new PCGenMessagePostbox();
	}
	
	public void addMember(PCGenMessageHandler plugin)
	{
		// Add the plugin to the chain of responsibility.
		chain.add(PCGenMessageHandler.class, plugin);
		postbox.handleMessage(new ComponentAddedMessage(this, plugin));
	}
	
	public void removeMember(PCGenMessageHandler plugin)
	{
		postbox.handleMessage(new ComponentRemovedMessage(this, plugin));
		// Remove the plugin from the chain of responsibility.
		chain.remove(PCGenMessageHandler.class, plugin);
	}

	
	/**
	 * @return the postbox to be used to despatch messages 
	 */
	public PCGenMessageHandler getPostbox()
	{
		return postbox;
	}

	/* ------------------------------------------------------------- */
	
	/**
	 * The Class {@code PCGenMessagePostbox} distributes PCGenMessages
	 * to all handlers registered in the parent ChainOfResponsibility. The handlers 
	 * are advised in order (with the source of the message advised last) however 
	 * messages may be consumed in which case no further handlers are advised of 
	 * the message.
	 */
	private final class PCGenMessagePostbox implements PCGenMessageHandler
	{

		@Override
		public void handleMessage(PCGenMessage msg)
		{
			// Guaranteed to return a non-null array
			Object[] listeners = chain.getListenerList();
			boolean sourceListening = false;
			// Process the listeners first to last, notifying
			// those that are interested in this event
			for (int i = 0; i < listeners.length - 1; i += 2)
			{
				if (listeners[i] == PCGenMessageHandler.class)
				{
					PCGenMessageHandler handler =
							(PCGenMessageHandler) listeners[i + 1];
					if (handler == msg.getSource())
					{
						sourceListening = true;
					}
					else
					{
						handler.handleMessage(msg);
						if (msg.isConsumed())
						{
							// Consumed, so we don't send the message to any more handlers 
							break;
						}
					}
				}
			}

			// The source gets advised of the message last, but only if it is listening
			if (!msg.isConsumed() && sourceListening)
			{
				((PCGenMessageHandler) msg.getSource()).handleMessage(msg);
			}
		}
		
	}
}