Copyright (c) 2005, 2006 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, 2006 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.registry.osgi;

import org.eclipse.core.internal.registry.RegistryMessages;
import org.eclipse.core.internal.runtime.RuntimeLog;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
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;

The class contains a set of helper methods for the runtime content plugin.
The closeServices() method should be called before the plugin is stopped.
Since:
org.eclipse.equinox.registry 3.2/**
 * The class contains a set of helper methods for the runtime content plugin.
 * The closeServices() method should be called before the plugin is stopped.
 *
 * @since org.eclipse.equinox.registry 3.2
 */
public class OSGIUtils {
	private ServiceTracker<?, ?> debugTracker = null;
	private ServiceTracker<?, ?> bundleTracker = null;
	private ServiceTracker<?, ?> configurationLocationTracker = null;

	// OSGI system properties.  Copied from EclipseStarter
	public static final String PROP_CONFIG_AREA = "osgi.configuration.area"; //$NON-NLS-1$
	public static final String PROP_INSTANCE_AREA = "osgi.instance.area"; //$NON-NLS-1$

	private static final OSGIUtils singleton = new OSGIUtils();

	public static OSGIUtils getDefault() {
		return singleton;
	}

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

	private void initServices() {
		BundleContext context = Activator.getContext();
		if (context == null) {
			RuntimeLog.log(new Status(IStatus.ERROR, RegistryMessages.OWNER_NAME, 0, RegistryMessages.bundle_not_activated, null));
			return;
		}

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

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

		// locations
		final String FILTER_PREFIX = "(&(objectClass=org.eclipse.osgi.service.datalocation.Location)(type="; //$NON-NLS-1$
		Filter filter = null;
		try {
			filter = context.createFilter(FILTER_PREFIX + PROP_CONFIG_AREA + "))"); //$NON-NLS-1$
		} catch (InvalidSyntaxException e) {
			// ignore this.  It should never happen as we have tested the above format.
		}
		configurationLocationTracker = new ServiceTracker<>(context, filter, null);
		configurationLocationTracker.open();

	}

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

	public boolean getBooleanDebugOption(String option, boolean defaultValue) {
		if (debugTracker == null) {
			RuntimeLog.log(new Status(IStatus.ERROR, RegistryMessages.OWNER_NAME, 0, RegistryMessages.bundle_not_activated, null));
			return defaultValue;
		}
		DebugOptions options = (DebugOptions) debugTracker.getService();
		if (options != null) {
			String value = options.getOption(option);
			if (value != null)
				return value.equalsIgnoreCase("true"); //$NON-NLS-1$
		}
		return defaultValue;
	}

	public PackageAdmin getPackageAdmin() {
		if (bundleTracker == null) {
			RuntimeLog.log(new Status(IStatus.ERROR, RegistryMessages.OWNER_NAME, 0, RegistryMessages.bundle_not_activated, null));
			return null;
		}
		return (PackageAdmin) bundleTracker.getService();
	}

	public Bundle getBundle(String bundleName) {
		PackageAdmin packageAdmin = getPackageAdmin();
		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 Bundle[] getFragments(Bundle bundle) {
		PackageAdmin packageAdmin = getPackageAdmin();
		if (packageAdmin == null)
			return null;
		return packageAdmin.getFragments(bundle);
	}

	public boolean isFragment(Bundle bundle) {
		PackageAdmin packageAdmin = getPackageAdmin();
		if (packageAdmin == null)
			return false;
		return (packageAdmin.getBundleType(bundle) & PackageAdmin.BUNDLE_TYPE_FRAGMENT) > 0;
	}

	public Bundle[] getHosts(Bundle bundle) {
		PackageAdmin packageAdmin = getPackageAdmin();
		if (packageAdmin == null)
			return null;
		return packageAdmin.getHosts(bundle);
	}

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