/*******************************************************************************
 * Copyright (c) 2005, 2006 IBM Corporation and others.
 * 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.core.runtime.internal.adaptor;

import org.eclipse.core.runtime.adaptor.EclipseAdaptorMsg;
import org.eclipse.core.runtime.adaptor.EclipseStarter;
import org.eclipse.osgi.framework.internal.core.FrameworkProperties;
import org.eclipse.osgi.internal.profile.Profile;
import org.eclipse.osgi.service.runnable.*;
import org.osgi.framework.*;

public class EclipseAppLauncher implements ApplicationLauncher {
	private ParameterizedRunnable runnable = null;
	private Object appContext = null;
	private Semaphore runningLock = new Semaphore(1);
	private Semaphore waitForAppLock = new Semaphore(0);
	private BundleContext context;
	private boolean relaunch = false;
	private boolean failOnNoDefault = false;
	public EclipseAppLauncher(BundleContext context, boolean relaunch, boolean failOnNoDefault) {
		this.context = context;
		this.relaunch = relaunch;
		this.failOnNoDefault = failOnNoDefault;
		findRunnableService();
	}

	/*
	 * Used for backwards compatibility with < 3.2 runtime
	 */
	private void findRunnableService() {
		// look for a ParameterizedRunnable registered as a service by runtimes (3.0, 3.1)
		String appClass = ParameterizedRunnable.class.getName();
		ServiceReference[] runRefs = null;
		try {
			runRefs = context.getServiceReferences(ParameterizedRunnable.class.getName(), "(&(objectClass=" + appClass + ")(eclipse.application=*))");
		} catch (InvalidSyntaxException e) {
			// ignore this.  It should never happen as we have tested the above format.
		}
		if (runRefs != null && runRefs.length > 0) {
			// found the service use it as the application.
			runnable = (ParameterizedRunnable) context.getService(runRefs[0]);
			// we will never be able to relaunch with a pre 3.2 runtime
			relaunch = false;
			waitForAppLock.release();
		}
	}

	/*
	 * Starts this application launcher on the current thread.  This method
	 * should be called by the main thread to ensure that applications are 
	 * launched in the main thread.
	 */
	public Object start(Object defaultContext) throws Exception {
		// here we assume that launch has been called by runtime before we started
		// TODO this may be a bad assumption but it works for now because we register the app launcher as a service and runtime synchronously calls launch on the service
		if (failOnNoDefault && runnable == null)
			throw new IllegalStateException(EclipseAdaptorMsg.ECLIPSE_STARTUP_ERROR_NO_APPLICATION);
		Object result = null;
		do {
			result = runApplication(defaultContext);
		} while (relaunch && (context.getBundle().getState() & Bundle.ACTIVE) != 0);
		return result;
	}

	/*
	 * Waits for an application to be launched and the runs the application on the
	 * current thread (main).
	 */
	private Object runApplication(Object defaultContext) throws Exception {
		// wait for an application to be launched.
		waitForAppLock.acquire();
		// an application is ready; acquire the running lock.
		// this must happen after we have acquired an application (by acquiring waitForAppLock above).
		runningLock.acquire();
		if (EclipseStarter.debug) {
			String timeString = FrameworkProperties.getProperty("eclipse.startTime"); //$NON-NLS-1$ 
			long time = timeString == null ? 0L : Long.parseLong(timeString);
			System.out.println("Starting application: " + (System.currentTimeMillis() - time)); //$NON-NLS-1$ 
		}
		if (Profile.PROFILE && (Profile.STARTUP || Profile.BENCHMARK))
			Profile.logTime("EclipseStarter.run(Object)()", "framework initialized! starting application..."); //$NON-NLS-1$ //$NON-NLS-2$
		try {
			// run the actual application on the current thread (main).
			return runnable.run(appContext != null ? appContext : defaultContext);
		} finally {
			if (Profile.PROFILE && Profile.STARTUP)
				Profile.logExit("EclipseStarter.run(Object)()"); //$NON-NLS-1$
			// free the runnable application and release the lock to allow another app to be launched.
			runnable = null;
			appContext = null;
			runningLock.release();
		}
	}

	public void launch(ParameterizedRunnable app, Object appContext) {
		waitForAppLock.acquire(-1); // clear out any pending apps notifications
		if (!runningLock.acquire(-1)) // check to see if an application is currently running
			throw new IllegalStateException("An application is aready running."); //$NON-NLS-1$
		this.runnable = app;
		this.appContext = appContext;
		waitForAppLock.release(); // notify the main thread to launch an application.
		runningLock.release(); // release the running lock
	}

	public void shutdown() {
		// this method will aquire and keep the runningLock to prevent
		// all future application launches.
		if (runningLock.acquire(-1))
			return; // no application is currently running.
		if (runnable instanceof ApplicationRunnable) {
			((ApplicationRunnable)runnable).stop();
			runningLock.acquire(60000); // timeout after 1 minute.
		}
	}
}