/*******************************************************************************

 * Copyright (c) 2010 Philipp Kursawe.

 * 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:

 *   Philipp Kursawe (phil.kursawe@gmail.com) - initial API and implementation

 ******************************************************************************/

package clipboard.monitor.component;



import org.osgi.framework.BundleContext;

import org.osgi.framework.InvalidSyntaxException;

import org.osgi.framework.ServiceReference;



import clipboard.monitor.ClipboardEvent;

import clipboard.monitor.ClipboardListener;

import clipboard.monitor.ClipboardMonitor;



/**

 * Abstract base class for clipboard monitor OSGi components.

 * 

 * 

 * @author <a href="mailto:phil.kursawe@gmail.com">Philipp Kursawe</a>

 * 

 */

public abstract class ClipboardMonitorComponent implements ClipboardMonitor {



	private ClipboardMonitor monitor;

	private BundleContext bundleContext;



	/**

	 * Subclasses must return the monitor to use with this component here. This

	 * method is called only once. The implementation does not need to remember

	 * what it returns. Must <em>not</em> return <code>null</code>.

	 */

	protected abstract ClipboardMonitor getMonitor();



	private ClipboardMonitor _getMonitor() {

		if (null == monitor) {

			monitor = getMonitor();

			if (null == monitor) {

				throw new IllegalArgumentException("monitor must not be null"); //$NON-NLS-1$

			}

		}

		return monitor;

	}



	protected void activate(BundleContext context) {

		this.bundleContext = context;

		start();

	}



	protected void deactivate() {

		stop();

	}



	public void start() {

		_getMonitor().start();

	}



	public void stop() {

		if (monitor != null) {

			monitor.stop();

			monitor = null;

		}

	}



	/**

	 * This method should be called by subclasses to send the event to

	 * registered service listeners.

	 * 

	 * @param event

	 */

	protected void onChange(ClipboardEvent event) {

		ServiceReference[] references = null;

		try {

			references = bundleContext.getServiceReferences(

					ClipboardListener.class.getName(), null);

		} catch (InvalidSyntaxException e) {

		}

		if (references != null) {

			for (ServiceReference ref : references) {

				ClipboardListener listener = (ClipboardListener) bundleContext

						.getService(ref);

				try {

					if (listener != null) {

						listener.onEvent(event);

					}

				} catch (Throwable t) {

				} finally {

					bundleContext.ungetService(ref);

				}

			}

		}

	}

}