/*
 * JBoss, Home of Professional Open Source
 * Copyright 2005-2008, Red Hat Middleware LLC, and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This 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 software 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 software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */ 

package org.jboss.messaging.core.postoffice.impl;

import org.jboss.messaging.core.logging.Logger;
import org.jboss.messaging.core.postoffice.FlowController;
import org.jboss.messaging.core.postoffice.PostOffice;
import org.jboss.messaging.core.server.ServerProducer;
import org.jboss.messaging.util.SimpleString;

import java.util.concurrent.ConcurrentLinkedQueue;

/**
 * 
 * A FlowControllerImpl
 * 
 * @author <a href="mailto:tim.fox@jboss.com">Tim Fox</a>
 *
 */
public class FlowControllerImpl implements FlowController
{
	private static final Logger log = Logger.getLogger(FlowControllerImpl.class);
	
	private int lastPot;
		
	private int creditPot;
	
	private final PostOffice postOffice;
	
	private final SimpleString address;
	
	private final java.util.Queue<ServerProducer> waitingList = new ConcurrentLinkedQueue<ServerProducer>();
	
	public FlowControllerImpl(final SimpleString address, final PostOffice postOffice) throws Exception
	{
		this.address = address;
		
		this.postOffice = postOffice;
	}
	
	public synchronized int getInitialCredits(final int windowSize, final ServerProducer producer) throws Exception
	{	     
      fillPot();
      
		int num = Math.min(windowSize, creditPot);
		
		creditPot -= num;
		
		if (num <= 0)
		{
			//Register producer as a waiter or will never get any messages
			
			producer.setWaiting(true);
			
			waitingList.add(producer);
		}
		
		return num;
	}
				
	//FIXME - sort out the synchronization on this - don't want to lock the whole thing
	//also don't want to execute the whole method if already waiting
	public synchronized void messageAcknowledged() throws Exception
	{		
//	   log.info("acking");
//	   
//		fillPot();
//		
//		log.info("Filled pot is now " + creditPot);
//			
//		while (creditPot > 0)
//		{
//			ServerProducer producer = waitingList.poll();
//			
//			if (producer == null)
//			{
//				break;
//			}
//			
//			producer.setWaiting(false);
//			
//			producer.requestAndSendCredits();
//		}					
	}
		
	public synchronized void requestAndSendCredits(final ServerProducer producer, final int credits) throws Exception
	{		
		if (creditPot <= 0)
		{
			if (!producer.isWaiting())
			{
				producer.setWaiting(true);
				
				waitingList.add(producer);
			}
		}
		else
		{
		   int creditsToTake = Math.min(credits, creditPot);
		   
			//creditPot -= creditsToTake;
			
			producer.sendCredits(creditsToTake);
		}
	}
			
	private void fillPot() throws Exception
	{
	 //TODO - for now we don't take max size into account
	   
//		List<Binding> bindings = postOffice.getBindingsForAddress(address);
//		
//		int minAvailable = Integer.MAX_VALUE;
//		
//		for (Binding binding: bindings)
//		{
//			Queue queue = binding.getQueue();
//			
//			int maxSize = queue.getMaxSizeBytes();
//			
//			
//			//log.info("max size is " + maxSize);
//			
//			int available;
//			
//			if (maxSize == -1)
//			{
//				available = Integer.MAX_VALUE;
//			}
//			else
//			{
//				available = maxSize - queue.getSizeBytes();
//				
//				log.info("Available is " + available);
//			}
//			
//			if (available < 0)
//			{
//				available = 0;
//			}
//			
//			minAvailable = Math.min(available, minAvailable);		
//			
//			log.info("min available is " + minAvailable);
//		}
//						
//		log.info("lastpot is " + lastPot);
//		if (minAvailable > lastPot)
//		{
//			creditPot += minAvailable - lastPot;
//			
//			lastPot = minAvailable;
//		}
		
		creditPot = Integer.MAX_VALUE;
	}
}