/*

  *   SONEWS News Server

  *   see AUTHORS for the list of contributors

  *

  *   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 3 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, see <http://www.gnu.org/licenses/>.

  */

 package org.sonews.util;

 import java.util.HashMap;

 import java.util.HashSet;

 import java.util.Map;

 import java.util.Set;

 import java.util.concurrent.ConcurrentHashMap;

 /**

  * Implementation of a Map that will loose its stored values after a 

  * configurable amount of time.

  * This class may be used to cache config values for example.

  * @author Christian Lins

  * @since sonews/0.5.0

  */

 public class TimeoutMap<K, V> extends ConcurrentHashMap<K, V>

 {

 	private static final long serialVersionUID = 453453467700345L;

 	private int timeout = 60000; // 60 sec

 	private transient Map<K, Long> timeoutMap = new HashMap<K, Long>();

 	/**

 	 * Constructor.

 	 * @param timeout Timeout in milliseconds

 	 */

 	public TimeoutMap(final int timeout)

 	{

 		this.timeout = timeout;

 	}

 	/**

 	 * Uses default timeout (60 sec).

 	 */

 	public TimeoutMap()

 	{

 	}

 	/**

 	 *

 	 * @param key

 	 * @return true if key is still valid.

 	 */

 	protected boolean checkTimeOut(Object key)

 	{

 		synchronized (this.timeoutMap) {

 			if (this.timeoutMap.containsKey(key)) {

 				long keytime = this.timeoutMap.get(key);

 				if ((System.currentTimeMillis() - keytime) < this.timeout) {

 					return true;

 				} else {

 					remove(key);

 					return false;

 				}

 			} else {

 				return false;

 			}

 		}

 	}

 	@Override

 	public boolean containsKey(Object key)

 	{

 		return checkTimeOut(key);

 	}

 	@Override

 	public synchronized V get(Object key)

 	{

 		if (checkTimeOut(key)) {

 			return super.get(key);

 		} else {

 			return null;

 		}

 	}

 	@Override

 	public V put(K key, V value)

 	{

 		synchronized (this.timeoutMap) {

 			removeStaleKeys();

 			this.timeoutMap.put(key, System.currentTimeMillis());

 			return super.put(key, value);

 		}

 	}

 	/**

 	 * @param arg0

 	 * @return

 	 */

 	@Override

 	public V remove(Object arg0)

 	{

 		synchronized (this.timeoutMap) {

 			this.timeoutMap.remove(arg0);

 			V val = super.remove(arg0);

 			return val;

 		}

 	}

 	protected void removeStaleKeys()

 	{

 		synchronized (this.timeoutMap) {

 			Set<Object> keySet = new HashSet<Object>(this.timeoutMap.keySet());

 			for (Object key : keySet) {

 				// The key/value is removed by the checkTimeOut() method if true

 				checkTimeOut(key);

 			}

 		}

 	}

 }