/*

 *   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);

      }

    }

  }

}