Copyright (c) 2005, 2015 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) 2005, 2015 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.core.internal.content;

import java.util.Hashtable;
import javax.xml.parsers.SAXParserFactory;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.content.IContentTypeManager;
import org.eclipse.osgi.service.debug.DebugOptions;
import org.osgi.framework.*;
import org.osgi.util.tracker.ServiceTracker;
import org.osgi.util.tracker.ServiceTrackerCustomizer;

The bundle activator for the runtime content manager plug-in.
/**
 * The bundle activator for the runtime content manager plug-in.
 */
public class Activator implements BundleActivator, ServiceTrackerCustomizer<IExtensionRegistry, IExtensionRegistry> {

	private static Activator singleton;
	private static BundleContext bundleContext;
	private ServiceRegistration<IContentTypeManager> contentManagerService;
	private ServiceTracker<SAXParserFactory, Object> parserTracker;
	private ServiceTracker<DebugOptions, Object> debugTracker;
	private ServiceTracker<IExtensionRegistry, IExtensionRegistry> registryTracker;

	
Return this activator's singleton instance or null if it has not been started.
/**
	 * Return this activator's singleton instance or null if it has not been started.
	 */
	public static Activator getDefault() {
		return singleton;
	}

	@Override
	public void start(BundleContext context) throws Exception {
		bundleContext = context;
		singleton = this;
		contentManagerService = bundleContext.registerService(IContentTypeManager.class, ContentTypeManager.getInstance(), new Hashtable<>());
		registryTracker = new ServiceTracker<>(context, IExtensionRegistry.class, this);
		registryTracker.open();
	}

	@Override
	public void stop(BundleContext context) throws Exception {
		if (contentManagerService != null) {
			contentManagerService.unregister();
			contentManagerService = null;
		}
		if (parserTracker != null) {
			parserTracker.close();
			parserTracker = null;
		}
		if (debugTracker != null) {
			debugTracker.close();
			debugTracker = null;
		}
		if (registryTracker != null) {
			registryTracker.close();
			registryTracker = null;
		}
		ContentTypeManager.shutdown();
		bundleContext = null;
	}

	
Return the registered SAX parser factory or null if one
does not exist.
/**
	 * Return the registered SAX parser factory or null if one
	 * does not exist.
	 */
	public SAXParserFactory getFactory() {
		if (parserTracker == null) {
			parserTracker = new ServiceTracker<>(bundleContext, SAXParserFactory.class, null);
			parserTracker.open();
		}
		SAXParserFactory theFactory = (SAXParserFactory) parserTracker.getService();
		if (theFactory != null)
			theFactory.setNamespaceAware(true);
		return theFactory;
	}

	
Return the boolean value in the debug options for the given key, or
return the default value if there is none.
/**
	 * Return the boolean value in the debug options for the given key, or
	 * return the default value if there is none.
	 */
	public boolean getBooleanDebugOption(String option, boolean defaultValue) {
		if (debugTracker == null) {
			debugTracker = new ServiceTracker<>(bundleContext, DebugOptions.class, null);
			debugTracker.open();
		}
		DebugOptions options = (DebugOptions) debugTracker.getService();
		if (options != null) {
			String value = options.getOption(option);
			if (value != null)
				return "true".equalsIgnoreCase(value); //$NON-NLS-1$
		}
		return defaultValue;
	}

	@Override
	public IExtensionRegistry addingService(ServiceReference<IExtensionRegistry> reference) {
		IExtensionRegistry registry = bundleContext.getService(reference);
		// registry is available; add the change listener
		ContentTypeManager.addRegistryChangeListener(registry);
		return registry;
	}

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

	@Override
	public void removedService(ServiceReference<IExtensionRegistry> reference, IExtensionRegistry service) {
		// registry is unavailable; remove the change listener
		ContentTypeManager.removeRegistryChangeListener(service);
		bundleContext.ungetService(reference);
	}
}