/*
 * Created on 17 Jul 2006
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program 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 General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package org.gudy.azureus2.core3.util;

import java.util.LinkedList;

public class 
AsyncDispatcher 
{
	private String					name;
	private AEThread2				thread;
	private int						priority	= Thread.NORM_PRIORITY;
	private AERunnable				queue_head;
	private LinkedList<AERunnable>	queue_tail;
	private AESemaphore				queue_sem 	= new AESemaphore( "AsyncDispatcher" );
	
	private int						num_priority;
	
	private int quiesce_after_millis;
	
	public
	AsyncDispatcher()
	{
		this( "AsyncDispatcher", 10000 );
	}
	
	public
	AsyncDispatcher(
		String		name )
	{
		this( name, 10000 );
	}
	
	public
	AsyncDispatcher(
		int		quiesce_after_millis )
	{
		this( "AsyncDispatcher", quiesce_after_millis );
	}
	
	public
	AsyncDispatcher(
		String		_name,
		int			_quiesce_after_millis )
	{
		name					= _name;
		quiesce_after_millis	= _quiesce_after_millis;
	}
	
	public void
	dispatch(
		AERunnable	target )
	{
		dispatch( target, false );
	}
	
	public void
	dispatch(
		AERunnable	target,
		boolean		is_priority )
	{
		synchronized( this ){
			
			if ( queue_head == null ){
				
				queue_head = target;
				
				if ( is_priority ){
					
					num_priority++;
				}
			}else{
				
				if ( queue_tail == null ){
					
					queue_tail = new LinkedList<AERunnable>();
				}
				
				if ( is_priority ){
				
					if ( num_priority == 0 ){
						
						queue_tail.add( 0, queue_head );
						
						queue_head = target;
						
					}else{
						
						queue_tail.add( num_priority-1, target );
					}
					
					num_priority++;
					
				}else{
				
					queue_tail.add( target );
				}
			}
			
			if ( thread == null ){
				
				thread = 
					new AEThread2( name, true )
					{
						public void
						run()
						{
							while( true ){
								
								queue_sem.reserve( quiesce_after_millis );
								
								AERunnable	to_run = null;
																
								synchronized( AsyncDispatcher.this ){
									
									if ( queue_head == null){
										
										queue_tail = null;
										
										thread = null;
										
										break;
									}
									
									to_run = queue_head;
									
									if ( queue_tail != null && !queue_tail.isEmpty()){
										
										queue_head = queue_tail.removeFirst();
										
									}else{
										
										queue_head = null;
									}
									
									if ( num_priority > 0 ){
										
										num_priority--;
									}
								}
								
								try{
									to_run.runSupport();
									
								}catch( Throwable e ){
									
									Debug.printStackTrace(e);
								}
							}
						}
					};
					
				thread.setPriority( priority );
				
				thread.start();
			}
		}
		
		queue_sem.release();
	}
	
	public boolean
	isQuiescent()
	{
		synchronized( this ){

			return( thread == null );
		}
	}
	
	public int
	getQueueSize()
	{
		synchronized( this ){

			int	result = queue_head == null?0:1;
			
			if ( queue_tail != null ){
				
				result += queue_tail.size();
			}
			
			return( result );
		}
	}
	
	public void
	setPriority(
		int		p )
	{
		priority = p;
	}
	
	public boolean
	isDispatchThread()
	{
		synchronized( this ){
			
			return( thread != null && thread.isCurrentThread());
		}
	}
}
