/*
 * Copyright (C) 2006-2008 Alfresco Software Limited.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 * As a special exception to the terms and conditions of version 2.0 of 
 * the GPL, you may redistribute this Program in connection with Free/Libre 
 * and Open Source Software ("FLOSS") applications as described in Alfresco's 
 * FLOSS exception.  You should have recieved a copy of the text describing 
 * the FLOSS exception, and it is also available here: 
 * http://www.alfresco.com/legal/licensing"
 */

package org.alfresco.jlan.server.thread;

import java.util.LinkedList;
import java.util.Vector;

/**
 * Thread Request Queue Class
 * 
 * <p>
 * Provides a request queue for a thread pool of worker threads.
 * 
 * @author gkspencer
 */
public class ThreadRequestQueue {

	// List of requests

	private LinkedList<ThreadRequest> m_queue;

	/**
	 * Class constructor
	 */
	public ThreadRequestQueue() {
		m_queue = new LinkedList<ThreadRequest>();
	}

	/**
	 * Return the number of requests in the queue
	 * 
	 * @return int
	 */
	public final int numberOfRequests() {
		return m_queue.size();
	}

	/**
	 * Add a request to the queue
	 * 
	 * @param req ThreadRequest
	 */
	public final void addRequest(ThreadRequest req) {

		synchronized ( m_queue) {
			
			// Add the request to the queue
	
			m_queue.add(req);
	
			// Notify a worker that there is a request to process
	
			m_queue.notify();
		}
	}

	/**
	 * Add requests to the queue
	 * 
	 * @param reqList Vector<ThreadRequest>
	 */
	public final void addRequests(Vector<ThreadRequest> reqList) {

		synchronized ( m_queue) {

			// Add the requests to the queue
			
			for ( int i = 0; i < reqList.size(); i++) {
				
				// Add the request to the queue
		
				m_queue.add(reqList.get( i));
		
				// Notify a worker that there is a request to process
		
				m_queue.notify();
			}
		}
	}

	/**
	 * Remove a request from the head of the queue
	 * 
	 * @return ThreadRequest
	 * @exception InterruptedException
	 */
	public final ThreadRequest removeRequest()
		throws InterruptedException {

		synchronized ( m_queue) {
			
			// Wait until there is a request
	
			while ( m_queue.size() == 0)
				m_queue.wait();
	
			// Get the request from the head of the queue
	
			return m_queue.poll();
		}
	}

	/**
	 * Wait for a request to be added to the queue
	 * 
	 * @exception InterruptedException
	 */
	public final void waitWhileEmpty()
		throws InterruptedException {

		synchronized ( m_queue) {
			
			// Wait until some work arrives on the queue
	
			while (m_queue.size() == 0)
				m_queue.wait();
		}
	}

	/**
	 * Wait for the request queue to be emptied
	 * 
	 * @exception InterruptedException
	 */
	public final void waitUntilEmpty()
		throws InterruptedException {

		synchronized ( m_queue) {
			
			// Wait until the request queue is empty
	
			while (m_queue.size() != 0)
				m_queue.wait();
		}
	}
}