/*
 * Part of the CCNx Java Library.
 *
 * Copyright (C) 2010 Palo Alto Research Center, Inc.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 * This library 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
 * Lesser General Public License for more details. You should have received
 * a copy of the GNU Lesser General Public License along with this library;
 * if not, write to the Free Software Foundation, Inc., 51 Franklin Street,
 * Fifth Floor, Boston, MA 02110-1301 USA.
 */

package org.ccnx.ccn.io.content;

import java.io.IOException;
import java.util.logging.Level;

import org.ccnx.ccn.impl.support.Log;
import org.ccnx.ccn.profiles.repo.RepositoryControl;

/**
 * A listener for a network object that requests a local repository to hold
 * a copy of the object whenever it is updated or saved.  A local repository
 * is one connected directly to the same ccnd as the application; it may have 
 * a distinguished role as the repository that is always available 
 * for local configuration data regardless of external connectivity. If there
 * is more than one repository that is local, the behavior is undefined.
 * 
 * To add this functionality to an existing network object, add an instance of this
 * class as a listener on the object. 
 */
public class LocalCopyListener implements UpdateListener {
	
	protected static LocalCopyListener backupListener = new LocalCopyListener();
	
	public static void startBackup(CCNNetworkObject<?> objectToSyncToRepository) throws IOException {
		
		// addListener will check for already having the listener. Check here,
		// though, to skip the localCopy if we already are listening for updates.
		if (objectToSyncToRepository.hasListener(backupListener)) {
			return;
		}
		
		if (objectToSyncToRepository.isSaved()) {
			if (Log.isLoggable(Log.FAC_IO, Level.INFO)) {
				Log.info(Log.FAC_IO, "startBackup: backing up previously-retrieved object version {0}", objectToSyncToRepository.getVersionedName());
			}
			backupListener.localCopy(objectToSyncToRepository);
		}
		objectToSyncToRepository.addListener(backupListener);
	}

	public void newVersionAvailable(CCNNetworkObject<?> newVersion, boolean wasSave) {
		// We probably want to make a local copy regardless, as the save might have been raw,
		// or not hit our local repository.
		localCopy(newVersion);
	}
	
	protected void localCopy(CCNNetworkObject<?> newVersion) {
		try {
			if (Log.isLoggable(Log.FAC_IO, Level.INFO)) {
				Log.info(Log.FAC_IO, "Synchronizing object to repository: {0}", newVersion.getVersionedName());
			}
			
			RepositoryControl.localRepoSync(newVersion.getHandle(), newVersion);
			
		} catch (IOException e) {
			if (Log.isLoggable(Log.FAC_IO, Level.INFO)) {
				Log.info(Log.FAC_IO, "Local repo sync failed for network object: " + e.getMessage());
				Log.logException("Local repo sync failed for network object: ", e);
			}
		}
	}


}