Copyright (c) 2007, 2018 IBM Corporation and others.
 This program and the accompanying materials
 are made available under the terms of the Eclipse Public License 2.0
 which accompanies this distribution, and is available at
 https://www.eclipse.org/legal/epl-2.0/
 SPDX-License-Identifier: EPL-2.0
 Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2007, 2018 IBM Corporation and others.
 *
 *  This program and the accompanying materials
 *  are made available under the terms of the Eclipse Public License 2.0
 *  which accompanies this distribution, and is available at
 *  https://www.eclipse.org/legal/epl-2.0/
 *
 *  SPDX-License-Identifier: EPL-2.0
 * 
 *  Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.equinox.internal.app;

import org.eclipse.osgi.framework.log.FrameworkLogEntry;
import org.eclipse.osgi.service.runnable.ApplicationRunnable;
import org.eclipse.osgi.util.NLS;
import org.osgi.framework.ServiceReference;
import org.osgi.service.application.ApplicationHandle;
import org.osgi.util.tracker.ServiceTracker;
import org.osgi.util.tracker.ServiceTrackerCustomizer;

Listens for the default ApplicationHandle which run on any thread to be destroyed.  This is used to force the main
thread to wait while a default application runs on another thread.
A main threaded application may be launched using this class to launch the main threaded application.
/**
 * Listens for the default ApplicationHandle which run on any thread to be destroyed.  This is used to force the main
 * thread to wait while a default application runs on another thread.
 * 
 * A main threaded application may be launched using this class to launch the main threaded application.
 */
public class DefaultApplicationListener implements ApplicationRunnable, ServiceTrackerCustomizer {
	private boolean running = true; // indicates the default application is running
	private EclipseAppHandle launchMainApp; // a handle to a main threaded application
	private final ServiceTracker handleTracker; // tracks the default application handle
	private Object result; // holds the result from the default application

	public DefaultApplicationListener(EclipseAppHandle defaultApp) {
		ServiceReference defaultRef = defaultApp.getServiceReference();
		if (defaultRef == null) {
			// service has been unregistered; application has ended already, 
			// save the result for latter
			result = defaultApp.waitForResult(100);
			handleTracker = null;
			return;
		}
		ServiceTracker defaultAppTracker = new ServiceTracker(Activator.getContext(), defaultRef, this);
		defaultAppTracker.open();
		EclipseAppHandle trackedApp = (EclipseAppHandle) defaultAppTracker.getService();
		if (trackedApp == null) {
			// close tracker since we do not care about tracking the app (bug 215764)
			defaultAppTracker.close();
			// service has been unregistered; application has ended aready,
			// save the result for latter
			result = defaultApp.waitForResult(100);
			handleTracker = null;
		} else {
			handleTracker = defaultAppTracker;
		}
	}

	@Override
	public Object run(Object context) {
		if (handleTracker == null)
			return getResult(); // app has ended, return the result
		EclipseAppHandle anyThreadedDefaultApp = (EclipseAppHandle) handleTracker.getService();
		if (anyThreadedDefaultApp != null)
			// We now need to actual launch the application; this will run the application on another thread.
			AnyThreadAppLauncher.launchEclipseApplication(anyThreadedDefaultApp);
		try {
			while (waitOnRunning()) {
				EclipseAppHandle mainHandle = getMainHandle();
				if (mainHandle != null) {
					// while we were waiting for the default application to end someone asked for a main threaded app to launch
					// note that we cannot hold the this lock while launching a main threaded application
					try {
						mainHandle.run(null);
					} catch (Throwable e) {
						String message = NLS.bind(Messages.application_error_starting, mainHandle.getInstanceId());
						Activator.log(new FrameworkLogEntry(Activator.PI_APP, FrameworkLogEntry.WARNING, 0, message, 0, e, null));
					}
					unsetMainHandle(mainHandle);
				}
			}
		} finally {
			handleTracker.close();
		}
		return getResult();
	}

	private synchronized EclipseAppHandle getMainHandle() {
		return launchMainApp;
	}

	private synchronized void unsetMainHandle(EclipseAppHandle mainHandle) {
		if (launchMainApp == mainHandle)
			launchMainApp = null;
	}

	private synchronized boolean waitOnRunning() {
		if (!running)
			return false;
		try {
			wait(100);
		} catch (InterruptedException e) {
			// do nothing
		}
		return running;
	}

	@Override
	public void stop() {
		if (handleTracker == null)
			return;
		// force the default application to quit
		ApplicationHandle handle = (ApplicationHandle) handleTracker.getService();
		if (handle != null) {
			try {
				handle.destroy();
			} catch (Throwable t) {
				String message = NLS.bind(Messages.application_error_stopping, handle.getInstanceId());
				Activator.log(new FrameworkLogEntry(Activator.PI_APP, FrameworkLogEntry.WARNING, 0, message, 0, t, null));
			}
		}
	}

	@Override
	public Object addingService(ServiceReference reference) {
		return Activator.getContext().getService(reference);
	}

	@Override
	public void modifiedService(ServiceReference reference, Object service) {
		// do nothing
	}

	@Override
	synchronized public void removedService(ServiceReference reference, Object service) {
		running = false;
		// only wait for 5 seconds; this may timeout if forcing an application to quit takes too long
		// this should never timeout if the application exited normally.
		result = ((EclipseAppHandle) service).waitForResult(5000);
		EclipseAppHandle mainHandle = getMainHandle();
		if (mainHandle != null)
			// default application has quit; now force the main threaded application to quit
			try {
				mainHandle.destroy();
			} catch (Throwable t) {
				String message = NLS.bind(Messages.application_error_stopping, mainHandle.getInstanceId());
				Activator.log(new FrameworkLogEntry(Activator.PI_APP, FrameworkLogEntry.WARNING, 0, message, 0, t, null));
			}
		this.notify();
	}

	synchronized void launch(EclipseAppHandle app) {
		launchMainApp = app;
		this.notify();
	}

	private synchronized Object getResult() {
		return result;
	}
}