EDIT

// $Id$

/**

* Copyright (C) 2007 EDIT

* European Distributed Institute of Taxonomy 

* http://www.e-taxonomy.eu

* 

* The contents of this file are subject to the Mozilla Public License Version 1.1

* See LICENSE.TXT at the top of this package for the full license terms.

*/

package eu.etaxonomy.cdm.persistence.hibernate;

import java.util.HashSet;

import java.util.Set;

import org.apache.log4j.Logger;

import org.hibernate.event.spi.PostDeleteEvent;

import org.hibernate.event.spi.PostDeleteEventListener;

import org.hibernate.event.spi.PostInsertEvent;

import org.hibernate.event.spi.PostInsertEventListener;

import org.hibernate.event.spi.PostLoadEvent;

import org.hibernate.event.spi.PostLoadEventListener;

import org.hibernate.event.spi.PostUpdateEvent;

import org.hibernate.event.spi.PostUpdateEventListener;

import eu.etaxonomy.cdm.model.common.CdmBase;

/**

 * ICdmPostDataChangeObserver implementors may register for this listener and their update() will 

 * be called after any CRUD (Create, Retrieve, Update, Delete).

 * 

 * Only events whose entities are of type CdmBase will be propagated

 * 

 * TODO Manage this class via Spring

 * 

 * @author n.hoffmann

 * @created 24.03.2009

 * @version 1.0

 */

public class CdmPostDataChangeObservableListener implements 

		  PostDeleteEventListener

		, PostInsertEventListener

		, PostLoadEventListener

		, PostUpdateEventListener

{

	private static final long serialVersionUID = -8764348096490526927L;

	@SuppressWarnings("unused")

	private static final Logger logger = Logger.getLogger(CdmPostDataChangeObservableListener.class);

	/**

	 * if this is set to true, observers have to be notified manually by calling 

	 * {@link #delayedNotify()}. All events until then will be stored in {@link #changeEvents}

	 */

	private boolean delayed;

	/**

	 * Define what events will be propagated

	 */

	private boolean propagateLoads = false,

					propagateInserts = true,

					propagateUpdates = true,

					propagateDeletes = true;

	/**

	 * DataChangeEvents get stored in this list for delayed propagation

	 */

	private CdmDataChangeMap changeEvents;

	/**

	 * Observing objects 

	 */

	private Set<ICdmPostDataChangeObserver> observers = new HashSet<ICdmPostDataChangeObserver>();

	/**

	 * Singleton instance

	 */

	private static CdmPostDataChangeObservableListener instance;

	/**

	 * @return the singleton CdmPostDataChangeObservableListener

	 */

	public static CdmPostDataChangeObservableListener getDefault(){

		if(instance == null){			

			instance = new CdmPostDataChangeObservableListener();

			// TODO set these properties via Spring

			// get the delayed version by default

			instance.setDelayed(true);

			// omit load events from propagation

			instance.setPropagateLoads(false);

		}

		return instance;

	}

	/**

	 * Register for updates

	 * 

	 * @param observer

	 */

	public void register(ICdmPostDataChangeObserver observer){

		getDefault().observers.add(observer);

	}

	/**

	 * Remove observer from notify queue

	 * @param observer

	 */

	public void unregister(ICdmPostDataChangeObserver observer){

		getDefault().observers.remove(observer);

	}

	public void delayedNotify(){

		if(delayed && changeEvents.size() > 0){

			Set<ICdmPostDataChangeObserver> modificationSaveObservers 

						= new HashSet<ICdmPostDataChangeObserver>(observers);

			for( ICdmPostDataChangeObserver observer : modificationSaveObservers){

				observer.update(changeEvents);

			}

			changeEvents.clear();

		}

	}

	/**

	 * Propagates the event to all registered objects.

	 * 

	 * @param event

	 */

	private void notifyObservers(CdmDataChangeEvent event){

		for( ICdmPostDataChangeObserver observer : observers){

			if(delayed){

				// store event for delayed propagation

				changeEvents.add(event.getEventType(), event);

			}else{

				// propagate event directly

				CdmDataChangeMap tmpMap = new CdmDataChangeMap();

				tmpMap.add(event.getEventType(), event);

				observer.update(tmpMap);

			}

		}

	}

	@Override

	public void onPostInsert(PostInsertEvent event) {

		if(propagateInserts && event.getEntity() instanceof CdmBase){

			getDefault().notifyObservers(CdmDataChangeEvent.NewInstance(event));

		}

	}

	@Override

	public void onPostLoad(PostLoadEvent event) {

		if(propagateLoads && event.getEntity() instanceof CdmBase){

			getDefault().notifyObservers(CdmDataChangeEvent.NewInstance(event));

		}

	}

	@Override

	public void onPostUpdate(PostUpdateEvent event) {

		if(propagateUpdates && event.getEntity() instanceof CdmBase){

			getDefault().notifyObservers(CdmDataChangeEvent.NewInstance(event));

		}

	}

	@Override

	public void onPostDelete(PostDeleteEvent event) {

		if(propagateDeletes && event.getEntity() instanceof CdmBase){

			getDefault().notifyObservers(CdmDataChangeEvent.NewInstance(event));

		}

	}

	/**

	 * @return the delayed

	 */

	public boolean isDelayed() {

		return delayed;

	}

	/**

	 * @param delayed the delayed to set

	 */

	public void setDelayed(boolean delayed) {

		if(delayed && changeEvents == null){

			changeEvents = new CdmDataChangeMap();

		}

		this.delayed = delayed;

	}

	/**

	 * @return the propagateLoads

	 */

	public boolean isPropagateLoads() {

		return propagateLoads;

	}

	/**

	 * @param propagateLoads the propagateLoads to set

	 */

	public void setPropagateLoads(boolean propagateLoads) {

		this.propagateLoads = propagateLoads;

	}

	/**

	 * @return the propagateInserts

	 */

	public boolean isPropagateInserts() {

		return propagateInserts;

	}

	/**

	 * @param propagateInserts the propagateInserts to set

	 */

	public void setPropagateInserts(boolean propagateInserts) {

		this.propagateInserts = propagateInserts;

	}

	/**

	 * @return the propagateUpdates

	 */

	public boolean isPropagateUpdates() {

		return propagateUpdates;

	}

	/**

	 * @param propagateUpdates the propagateUpdates to set

	 */

	public void setPropagateUpdates(boolean propagateUpdates) {

		this.propagateUpdates = propagateUpdates;

	}

	/**

	 * @return the propagateDeletes

	 */

	public boolean isPropagateDeletes() {

		return propagateDeletes;

	}

	/**

	 * @param propagateDeletes the propagateDeletes to set

	 */

	public void setPropagateDeletes(boolean propagateDeletes) {

		this.propagateDeletes = propagateDeletes;

	}

}