//
//  ========================================================================
//  Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.util.thread;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/* ------------------------------------------------------------ */
/** Timeout queue.
 * This class implements a timeout queue for timers that are at least as likely to be cancelled as they are to expire.
 * Unlike the util timeout class, the duration of the timeouts is shared by all scheduled tasks and if the duration 
 * is changed, this affects all scheduled tasks.
 * <p>
 * The nested class Task should be extended by users of this class to obtain call back notification of 
 * expires. 
 */
public class Timeout
{
	private static final Logger LOG = LoggerFactory.getLogger(Timeout.class);
	private Object _lock;
	private long _duration;
	private volatile long _now=System.currentTimeMillis();
	private Task _head=new Task();

	/* ------------------------------------------------------------ */
	public Timeout(Object lock)
	{
		_lock=lock;
		_head._timeout=this;
	}

	/* ------------------------------------------------------------ */
	/**
	 * @return Returns the duration.
	 */
	public long getDuration()
	{
		return _duration;
	}

	/* ------------------------------------------------------------ */
	/**
	 * @param duration The duration to set.
	 */
	public void setDuration(long duration)
	{
		_duration = duration;
	}

	/* ------------------------------------------------------------ */
	public long setNow()
	{
		return _now=System.currentTimeMillis();
	}
	
	/* ------------------------------------------------------------ */
	public long getNow()
	{
		return _now;
	}

	/* ------------------------------------------------------------ */
	public void setNow(long now)
	{
		_now=now;
	}

	/* ------------------------------------------------------------ */
	/** Get an expired tasks.
	 * This is called instead of {@link #tick()} to obtain the next
	 * expired Task, but without calling it's {@link Task#expire()} or
	 * {@link Task#expired()} methods.
	 * 
	 * @return the next expired task or null.
	 */

	public Task expired()
	{
		synchronized (_lock)
		{
			long _expiry = _now-_duration;
			if (_head._next!=_head)
			{
				Task task = _head._next;
				if (task._timestamp>_expiry)
					return null;

				task.unlink();
				task._expired=true;
				return task;
			}
			return null;
		}
	}

	public void cancelAll()
	{
		synchronized (_lock)
		{
			_head._next=_head._prev=_head;
		}
	}

	public long getTimeToNext()
	{
		synchronized (_lock)
		{
			if (_head._next==_head)
				return -1;
			long to_next = _duration+_head._next._timestamp-_now;
			return to_next<0?0:to_next;
		}
	}

	@Override
	public String toString()
	{
		StringBuffer buf = new StringBuffer();
		buf.append(super.toString());
		
		Task task = _head._next;
		while (task!=_head)
		{
			buf.append("-->");
			buf.append(task);
			task=task._next;
		}
		
		return buf.toString();
	}

	/* ------------------------------------------------------------ */
	/* ------------------------------------------------------------ */
	/* ------------------------------------------------------------ */
	/* ------------------------------------------------------------ */
	/** Task.
	 * The base class for scheduled timeouts.  This class should be
	 * extended to implement the expire() method, which is called if the
	 * timeout expires.
	 * 
	 * 
	 *
	 */
	public static class Task
	{
		Task _next;
		Task _prev;
		Timeout _timeout;
		long _timestamp=0;
		boolean _expired=false;

		protected Task()
		{
			_next=_prev=this;
		}

		private void unlink()
		{
			_next._prev=_prev;
			_prev._next=_next;
			_next=_prev=this;
			_expired=false;
		}
	}

}