/*******************************************************************************
 * 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.internal.registry.osgi;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ResourceBundle;
import javax.xml.parsers.SAXParserFactory;
import org.eclipse.core.internal.registry.*;
import org.eclipse.core.internal.runtime.ResourceTranslator;
import org.eclipse.core.runtime.*;
import org.eclipse.core.runtime.spi.*;
import org.eclipse.osgi.util.NLS;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
import org.osgi.util.tracker.ServiceTracker;

/**
 * The registry strategy that can be used in OSGi world. It provides the following functionality:
 * <p><ul>
 * <li>Translation is done with ResourceTranslator</li>
 * <li>Registry is filled with information stored in plugin.xml / fragment.xml of OSGi bundles</li>
 * <li>Uses bunlde-based class loading to create executable extensions</li>
 * <li>Performs registry validation based on the time stamps of the plugin.xml / fragment.xml files</li>
 * <li>XML parser is obtained via an OSGi service</li>
 *  </ul></p>
 * @see RegistryFactory#setDefaultRegistryProvider(IRegistryProvider)
 * @since org.eclipse.equinox.registry 3.2
 */

public class RegistryStrategyOSGI extends RegistryStrategy {

	/**
	 * Registry access key
	 */
	private Object token;

	/**
	 * Debug extension registry
	 */
	protected boolean DEBUG;

	/**
	 * Debug extension registry events
	 */
	protected boolean DEBUG_REGISTRY_EVENTS;

	/**
	 * Tracker for the XML parser service
	 */
	private ServiceTracker xmlTracker = null;

	/**
	 * @param theStorageDir - array of file system directories to store cache files; might be null
	 * @param cacheReadOnly - array of read only attributes. True: cache at this location is read 
	 * only; false: cache is read/write
	 * @param key - control key for the registry (should be the same key as used in 
	 * the RegistryManager#createExtensionRegistry() of this registry
	 */
	public RegistryStrategyOSGI(File[] theStorageDir, boolean[] cacheReadOnly, Object key) {
		super(theStorageDir, cacheReadOnly);
		token = key;
	}

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#translate(java.lang.String, java.util.ResourceBundle)
	 */
	public final String translate(String key, ResourceBundle resources) {
		return ResourceTranslator.getResourceString(null, key, resources);
	}

	////////////////////////////////////////////////////////////////////////////////////////
	// Use OSGi bundles for namespace resolution (contributors: plugins and fragments)

	/**
	 * The default load factor for the bundle cache. 
	 */
	private static float DEFAULT_BUNDLECACHE_LOADFACTOR = 0.75f;

	/**
	 * The expected bundle cache size (calculated as a number of bundles divided 
	 * by the DEFAULT_BUNDLECACHE_LOADFACTOR). The bundle cache will be resized 
	 * automatically is this number is exceeded. 
	 */
	private static int DEFAULT_BUNDLECACHE_SIZE = 200;

	/**
	 * For performance, we cache mapping of IDs to Bundles.
	 * 
	 * We don't expect mapping to change during the runtime. (Or, in the OSGI terms,
	 * we don't expect bundle IDs to be reused during the Eclipse run.)
	 * The Bundle object is stored as a weak reference to facilitate GC
	 * in case the bundle was uninstalled during the Eclipse run.
	 */
	private ReferenceMap bundleMap = new ReferenceMap(ReferenceMap.SOFT, DEFAULT_BUNDLECACHE_SIZE, DEFAULT_BUNDLECACHE_LOADFACTOR);

	// String Id to OSGi Bundle conversion
	private Bundle getBundle(String id) {
		if (id == null)
			return null;
		long OSGiId;
		try {
			OSGiId = Long.parseLong(id);
		} catch (NumberFormatException e) {
			return null;
		}
		// We assume here that OSGI Id will fit into "int". As the number of 
		// registry elements themselves are expected to fit into "int", this
		// is a valid assumption for the time being.
		Bundle bundle = (Bundle) bundleMap.get((int) OSGiId);
		if (bundle != null)
			return bundle;
		bundle = Activator.getContext().getBundle(OSGiId);
		bundleMap.put((int) OSGiId, bundle);
		return bundle;
	}

	/////////////////////////////////////////////////////////////////////////////////////
	// Executable extensions: bundle-based class loading

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#createExecutableExtension(org.eclipse.core.runtime.spi.RegistryContributor, java.lang.String, java.lang.String)
	 */
	public Object createExecutableExtension(RegistryContributor contributor, String className, String overridenContributorName) throws CoreException {
		Bundle contributingBundle;
		if (overridenContributorName != null && !overridenContributorName.equals("")) //$NON-NLS-1$
			contributingBundle = OSGIUtils.getDefault().getBundle(overridenContributorName);
		else
			contributingBundle = getBundle(contributor.getId());

		if (contributingBundle == null)
			throwException(NLS.bind(RegistryMessages.plugin_loadClassError, "UNKNOWN BUNDLE", className), new InvalidRegistryObjectException()); //$NON-NLS-1$ 

		// load the requested class from this bundle
		Class classInstance = null;
		try {
			classInstance = contributingBundle.loadClass(className);
		} catch (Exception e1) {
			throwException(NLS.bind(RegistryMessages.plugin_loadClassError, contributingBundle.getSymbolicName(), className), e1);
		} catch (LinkageError e) {
			throwException(NLS.bind(RegistryMessages.plugin_loadClassError, contributingBundle.getSymbolicName(), className), e);
		}

		// create a new instance
		Object result = null;
		try {
			result = classInstance.newInstance();
		} catch (Exception e) {
			throwException(NLS.bind(RegistryMessages.plugin_instantiateClassError, contributingBundle.getSymbolicName(), className), e);
		}
		return result;
	}

	private void throwException(String message, Throwable exception) throws CoreException {
		throw new CoreException(new Status(IStatus.ERROR, RegistryMessages.OWNER_NAME, IRegistryConstants.PLUGIN_ERROR, message, exception));
	}

	/////////////////////////////////////////////////////////////////////////////////////
	// Start / stop extra processing: adding bundle listener; fill registry if not filled from cache

	/**
	 * Listening to the bundle events.
	 */
	private EclipseBundleListener pluginBundleListener = null;

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#onStart(org.eclipse.core.runtime.IExtensionRegistry)
	 */
	public void onStart(IExtensionRegistry registry) {
		super.onStart(registry);
		if (!(registry instanceof ExtensionRegistry))
			return;
		ExtensionRegistry theRegistry = (ExtensionRegistry) registry;

		// register a listener to catch new bundle installations/resolutions.
		pluginBundleListener = new EclipseBundleListener(theRegistry, token);
		Activator.getContext().addBundleListener(pluginBundleListener);

		// populate the registry with all the currently installed bundles.
		// There is a small window here while processBundles is being
		// called where the pluginBundleListener may receive a BundleEvent 
		// to add/remove a bundle from the registry.  This is ok since
		// the registry is a synchronized object and will not add the
		// same bundle twice.
		if (!theRegistry.filledFromCache())
			pluginBundleListener.processBundles(Activator.getContext().getBundles());
	}

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#onStop(org.eclipse.core.runtime.IExtensionRegistry)
	 */
	public void onStop(IExtensionRegistry registry) {
		if (pluginBundleListener != null)
			Activator.getContext().removeBundleListener(pluginBundleListener);
		if (xmlTracker != null) {
			xmlTracker.close();
			xmlTracker = null;
		}
		super.onStop(registry);
	}

	//////////////////////////////////////////////////////////////////////////////////////
	// Cache strategy

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#cacheUse()
	 */
	public boolean cacheUse() {
		return !"true".equals(RegistryProperties.getProperty(IRegistryConstants.PROP_NO_REGISTRY_CACHE)); //$NON-NLS-1$
	}

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#cacheLazyLoading()
	 */
	public boolean cacheLazyLoading() {
		return !("true".equalsIgnoreCase(RegistryProperties.getProperty(IRegistryConstants.PROP_NO_LAZY_CACHE_LOADING))); //$NON-NLS-1$
	}

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#getContributionsTimestamp()
	 */
	public long getContributionsTimestamp() {
		BundleContext context = Activator.getContext();
		if (context == null)
			return 0;
		// If the check config prop is false or not set then exit
		if (!"true".equalsIgnoreCase(context.getProperty(IRegistryConstants.PROP_CHECK_CONFIG))) //$NON-NLS-1$  
			return 0;
		Bundle[] allBundles = context.getBundles();
		long result = 0;
		for (int i = 0; i < allBundles.length; i++) {
			URL pluginManifest = allBundles[i].getEntry("plugin.xml"); //$NON-NLS-1$
			if (pluginManifest == null)
				pluginManifest = allBundles[i].getEntry("fragment.xml"); //$NON-NLS-1$
			if (pluginManifest == null)
				continue;
			try {
				URLConnection connection = pluginManifest.openConnection();
				result ^= connection.getLastModified() + allBundles[i].getBundleId();
			} catch (IOException e) {
				return 0;
			}
		}
		return result;
	}

	/* (non-Javadoc)
	 * @see org.eclipse.core.runtime.spi.RegistryStrategy#getXMLParser()
	 */
	public SAXParserFactory getXMLParser() {
		if (xmlTracker == null) {
			xmlTracker = new ServiceTracker(Activator.getContext(), SAXParserFactory.class.getName(), null);
			xmlTracker.open();
		}
		return (SAXParserFactory) xmlTracker.getService();
	}
}
