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/***********************************************************************************************************************
 *
 * blueMarine Metadata - open source media workflow
 * Copyright (C) 2007-2011 by Tidalwave s.a.s. (http://www.tidalwave.it)
 *
 ***********************************************************************************************************************
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations under the License.
 *
 ***********************************************************************************************************************
 *
 * WWW: http://bluemarine.tidalwave.it
 * SCM: https://kenai.com/hg/bluemarine~metadata-src
 *
 **********************************************************************************************************************/
package it.tidalwave.metadata.persistence.node.impl;

import javax.annotation.Nonnull;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;
import java.util.List;
import it.tidalwave.util.logging.Logger;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Timer;
import it.tidalwave.metadata.persistence.MetadataPersistence;
import it.tidalwave.metadata.persistence.event.MetadataPersistenceAdapter;
import it.tidalwave.metadata.persistence.event.MetadataPersistenceEvent;
import it.tidalwave.metadata.persistence.node.MetadataPersistenceNodeManager;

/*******************************************************************************
 *
 * This class listens for {@link MetadataPersistence} about properties that have
 * been persisted and updates the related nodes. The delivery is decoupled in
 * two ways:
 * 
 * 
 * First, the metadata events are delivered in a generic thread, while 
 *     nodes must be updated in the EDT thread.
 * Second, events are buffered and node update is delayed by a few seconds,
 *     in order to avoid wasting CPU for too frequent updates.
 * 
 * 
 * @author  Fabrizio Giudici
 * @version $Id$
 *
 ******************************************************************************/
public class MetadataNodeUpdater extends MetadataPersistenceAdapter
  {
    private static final String CLASS = MetadataNodeUpdater.class.getName();
    private static final Logger logger = Logger.getLogger(CLASS);
    
    private static final int PERIOD = 5000;
    
    /** The set of pending events. Being a set, duplicate events are merged,
     *  thus coalescing the events to deliver. */
    private final Set pendingEvents = new HashSet();
    
    // TODO: maybe refreshNode() could be added to the public interface of nodeManager?
    private final MetadataPersistenceNodeManagerImpl nodeManager = (MetadataPersistenceNodeManagerImpl)
                  MetadataPersistenceNodeManager.Locator.findMetadataPersistenceNodeManager();
            
    /***************************************************************************
     *
     *
     **************************************************************************/
    private final ActionListener actionListener = new ActionListener() 
      {
        public void actionPerformed (@Nonnull final ActionEvent e)
          {
            final List events = new ArrayList();
            
            synchronized (pendingEvents)
              {
                events.addAll(pendingEvents);
                pendingEvents.clear();
              }
            
            logger.fine(">>>> timer fired, now delivering %d events...", events.size());
            
            for (final MetadataPersistenceEvent event : events)
              {
                nodeManager.refreshNode(event.getPropertySetClass(), event.getPropertyName());
              }
          }
      };
    
    private final Timer timer = new Timer(PERIOD, actionListener);
    
    /***************************************************************************
     *
     *
     **************************************************************************/
    @Override
    public void notifyPropertyPersisted (@Nonnull final MetadataPersistenceEvent event)
      {
        synchronized (pendingEvents)
          {
            pendingEvents.add(event);
          }
       
        logger.finer("notifyPropertyPersisted(%s) - %d pending events", event, pendingEvents.size());
        
        if (!timer.isRunning())
          {
            logger.finest(">>>> restarting timer...");
            timer.setRepeats(false);
            timer.restart();
          }
      }
  }