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.preferences;

import org.eclipse.core.internal.preferences.exchange.ILegacyPreferences;
import org.eclipse.osgi.service.datalocation.Location;
import org.eclipse.osgi.service.debug.DebugOptions;
import org.osgi.framework.*;
import org.osgi.service.packageadmin.PackageAdmin;
import org.osgi.util.tracker.ServiceTracker;

This class contains a set of helper OSGI methods for the Preferences plugin.
The closeServices() method should be called before the plugin is stopped.
Since:
org.eclipse.equinox.preferences 3.2/**
 * This class contains a set of helper OSGI methods for the Preferences plugin.
 * The closeServices() method should be called before the plugin is stopped.
 *
 * @since org.eclipse.equinox.preferences 3.2
 */
public class PreferencesOSGiUtils {
	private ServiceTracker<?, ILegacyPreferences> initTracker;
	private ServiceTracker<?, DebugOptions> debugTracker;
	private ServiceTracker<?, PackageAdmin> bundleTracker;
	private ServiceTracker<?, ?> configurationLocationTracker;
	private ServiceTracker<?, ?> instanceLocationTracker;

	private static final PreferencesOSGiUtils singleton = new PreferencesOSGiUtils();

	public static PreferencesOSGiUtils getDefault() {
		return singleton;
	}

	
Private constructor to block instance creation.
/**
	 * Private constructor to block instance creation.
	 */
	private PreferencesOSGiUtils() {
		super();
	}

	void openServices() {
		BundleContext context = Activator.getContext();
		if (context == null) {
			if (EclipsePreferences.DEBUG_PREFERENCE_GENERAL)
				PrefsMessages.message("PreferencesOSGiUtils called before plugin started"); //$NON-NLS-1$
			return;
		}

		initTracker = new ServiceTracker<>(context, ILegacyPreferences.class, null);
		initTracker.open(true);

		debugTracker = new ServiceTracker<>(context, DebugOptions.class, null);
		debugTracker.open();

		bundleTracker = new ServiceTracker<>(context, PackageAdmin.class, null);
		bundleTracker.open();

		// locations

		Filter filter = null;
		try {
			filter = context.createFilter(Location.CONFIGURATION_FILTER);
		} catch (InvalidSyntaxException e) {
			// ignore this.  It should never happen as we have tested the above format.
		}
		configurationLocationTracker = new ServiceTracker<>(context, filter, null);
		configurationLocationTracker.open();

		try {
			filter = context.createFilter(Location.INSTANCE_FILTER);
		} catch (InvalidSyntaxException e) {
			// ignore this.  It should never happen as we have tested the above format.
		}
		instanceLocationTracker = new ServiceTracker<>(context, filter, null);
		instanceLocationTracker.open();
	}

	void closeServices() {
		if (initTracker != null) {
			initTracker.close();
			initTracker = null;
		}
		if (debugTracker != null) {
			debugTracker.close();
			debugTracker = null;
		}
		if (bundleTracker != null) {
			bundleTracker.close();
			bundleTracker = null;
		}
		if (configurationLocationTracker != null) {
			configurationLocationTracker.close();
			configurationLocationTracker = null;
		}
		if (instanceLocationTracker != null) {
			instanceLocationTracker.close();
			instanceLocationTracker = null;
		}
	}

	public ILegacyPreferences getLegacyPreferences() {
		if (initTracker != null)
			return initTracker.getService();
		if (EclipsePreferences.DEBUG_PREFERENCE_GENERAL)
			PrefsMessages.message("Legacy preference tracker is not set"); //$NON-NLS-1$
		return null;
	}

	public boolean getBooleanDebugOption(String option, boolean defaultValue) {
		if (debugTracker == null) {
			if (EclipsePreferences.DEBUG_PREFERENCE_GENERAL)
				PrefsMessages.message("Debug tracker is not set"); //$NON-NLS-1$
			return defaultValue;
		}
		DebugOptions options = debugTracker.getService();
		if (options != null) {
			String value = options.getOption(option);
			if (value != null)
				return value.equalsIgnoreCase("true"); //$NON-NLS-1$
		}
		return defaultValue;
	}

	public Bundle getBundle(String bundleName) {
		if (bundleTracker == null) {
			if (EclipsePreferences.DEBUG_PREFERENCE_GENERAL)
				PrefsMessages.message("Bundle tracker is not set"); //$NON-NLS-1$
			return null;
		}
		PackageAdmin packageAdmin = bundleTracker.getService();
		if (packageAdmin == null)
			return null;
		Bundle[] bundles = packageAdmin.getBundles(bundleName, null);
		if (bundles == null)
			return null;
		//Return the first bundle that is not installed or uninstalled
		for (Bundle bundle : bundles) {
			if ((bundle.getState() & (Bundle.INSTALLED | Bundle.UNINSTALLED)) == 0) {
				return bundle;
			}
		}
		return null;
	}

	public Location getConfigurationLocation() {
		if (configurationLocationTracker != null)
			return (Location) configurationLocationTracker.getService();
		return null;
	}

	public Location getInstanceLocation() {
		if (instanceLocationTracker != null)
			return (Location) instanceLocationTracker.getService();
		return null;
	}
}