/*******************************************************************************
 * Copyright (c) 2010, 2011 Obeo.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Obeo - initial API and implementation
 *******************************************************************************/
package org.eclipse.mylyn.docs.intent.collab.cdo.adapters;

import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;

import org.eclipse.emf.cdo.common.revision.CDORevisionKey;
import org.eclipse.emf.cdo.common.revision.delta.CDOFeatureDelta;
import org.eclipse.emf.cdo.common.revision.delta.CDORevisionDelta;
import org.eclipse.emf.cdo.session.CDOSessionInvalidationEvent;
import org.eclipse.emf.ecore.EClass;
import org.eclipse.emf.ecore.ENamedElement;
import org.eclipse.emf.ecore.EStructuralFeature;
import org.eclipse.mylyn.docs.intent.collab.handlers.notification.Notificator;
import org.eclipse.mylyn.docs.intent.collab.handlers.notification.RepositoryChangeNotification;
import org.eclipse.mylyn.docs.intent.collab.handlers.notification.RepositoryChangeNotificationFactoryHolder;
import org.eclipse.net4j.util.event.IEvent;
import org.eclipse.net4j.util.event.IListener;

/**
 * Listens for any change that occur on an instance of the given types, an notify the associated
 * TypeNotificator.
 * 
 * @author <a href="mailto:alex.lagarde@obeo.fr">Alex Lagarde</a>
 */
public class CDOTypeListener implements IListener {

	/**
	 * The type notificator to notify if changes are detected.
	 */
	private final Notificator listeningTypeNotificator;

	/**
	 * List of the types to listen.
	 */
	private final Set<EStructuralFeature> listennedTypes;

	/**
	 * CDOTypeListener constructor.
	 * 
	 * @param typeNotificator
	 *            The TypeNotificator to notify if changes are detected.
	 * @param types
	 *            List of the types to listen
	 */
	public CDOTypeListener(Notificator typeNotificator, Set<EStructuralFeature> types) {
		this.listeningTypeNotificator = typeNotificator;
		this.listennedTypes = new LinkedHashSet<EStructuralFeature>();
		this.listennedTypes.addAll(types);
	}

	/**
	 * {@inheritDoc}
	 * 
	 * @see org.eclipse.net4j.util.event.IListener#notifyEvent(org.eclipse.net4j.util.event.IEvent)
	 */
	public void notifyEvent(IEvent event) {

		// For each CDOSessionInvalidationEvent sent by the session whenever a "invalidate" message is
		// received (see CDO documentation).
		if (event instanceof CDOSessionInvalidationEvent) {
			CDOSessionInvalidationEvent invalidationEvent = (CDOSessionInvalidationEvent)event;
			boolean changesDetected = false;

			// We determine if this event concerns a type it listens.
			for (CDORevisionKey key : invalidationEvent.getChangedObjects()) {
				if (changesDetected) {
					break;
				}
				CDORevisionDelta revisionDelta = (CDORevisionDelta)key;

				for (CDOFeatureDelta delta : revisionDelta.getFeatureDeltas()) {

					if (isListenedTypeModification(delta.getFeature())) {
						changesDetected = true;
						break;
					}
				}
			}

			// If relevant changes have been detected, we send a notification to the typeNotificator
			if (changesDetected) {
				RepositoryChangeNotification newNotification = RepositoryChangeNotificationFactoryHolder
						.getChangeNotificationFactory().createRepositoryChangeNotification(invalidationEvent);
				if (newNotification != null) {
					this.listeningTypeNotificator.notifyHandlers(newNotification);
				}
			}

		}
	}

	/**
	 * Returns true if the given feature matches any listened types of this typeListener.
	 * 
	 * @param feature
	 *            the feature to test.
	 * @return true if the given feature matches any listened types of this typeListener, false otherwise.
	 */
	private boolean isListenedTypeModification(EStructuralFeature feature) {
		boolean isListennedType = false;

		for (Iterator<EStructuralFeature> iterator = listennedTypes.iterator(); iterator.hasNext()
				&& !isListennedType;) {
			ENamedElement listennedtype = iterator.next();
			if (listennedtype instanceof EStructuralFeature) {
				isListennedType = listennedtype.equals(feature);
			}
			if (listennedtype instanceof EClass) {
				isListennedType = ((EClass)listennedtype).getEAllStructuralFeatures().contains(feature);
			}
		}

		return isListennedType;
	}
}