/*
    * Copyright 2006-2008 the original author or authors.
    * 
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    * 
    *      http://www.apache.org/licenses/LICENSE-2.0
    * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.springframework.osgi.extender.internal.support;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.osgi.framework.Bundle;
  import org.osgi.framework.BundleContext;
  import org.osgi.framework.ServiceRegistration;
  import org.springframework.beans.factory.DisposableBean;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.beans.factory.xml.NamespaceHandlerResolver;
  import org.springframework.osgi.util.OsgiBundleUtils;
  import org.springframework.osgi.util.OsgiServiceUtils;
  import org.springframework.osgi.util.OsgiStringUtils;
  import org.springframework.util.Assert;
  import org.xml.sax.EntityResolver;
  
  /**
   * Support class that deals with namespace parsers discovered inside Spring
   * bundles.
   * 
   * @author Costin Leau
   * 
   */
  public class NamespaceManager implements InitializingBean, DisposableBean {
  
  	private static final Log log = LogFactory.getLog(NamespaceManager.class);
  
  	private static final String NS_HANDLER_RESOLVER_CLASS_NAME = NamespaceHandlerResolver.class.getName();
  
  	/**
  	 * The set of all namespace plugins known to the extender
  	 */
  	private NamespacePlugins namespacePlugins;
  
  	/**
  	 * ServiceRegistration object returned by OSGi when registering the
  	 * NamespacePlugins instance as a service
  	 */
  	private ServiceRegistration nsResolverRegistration, enResolverRegistration = null;
  
  	/**
  	 * OSGi Environment.
  	 */
  	private final BundleContext context;
  
  	private final String extenderInfo;
  
  	private static final String META_INF = "META-INF/";
  
  	private static final String SPRING_HANDLERS = "spring.handlers";
  
  	private static final String SPRING_SCHEMAS = "spring.schemas";
  
  
  	/**
  	 * Constructor.
  	 * 
  	 * @param extenderBundleContext
  	 */
  	public NamespaceManager(BundleContext context) {
  		this.context = context;
  
  		extenderInfo = context.getBundle().getSymbolicName() + "|"
  				+ OsgiBundleUtils.getBundleVersion(context.getBundle());
  
  		// detect package admin
  		this.namespacePlugins = new NamespacePlugins();
  	}
  
  	/**
  	 * If this bundle defines handler mapping or schema mapping resources, then
  	 * register it with the namespace plugin handler.
  	 * 
  	 * <p/> This method considers only the bundle space and not the class space.
  	 * 
  	 * @param bundle
  	 */
  	public void maybeAddNamespaceHandlerFor(Bundle bundle) {
  		// Ignore system bundle
  		if (OsgiBundleUtils.isSystemBundle(bundle)) {
  			return;
  		}
  
 		boolean hasHandlers = bundle.findEntries(META_INF, SPRING_HANDLERS, false) != null;
 		boolean hasSchemas = bundle.findEntries(META_INF, SPRING_SCHEMAS, false) != null;
 
 		// if the bundle defines handlers
 		if (hasHandlers) {
 			// check type compatibility between the bundle's and spring-extender's spring version
 			if (hasCompatibleNamespaceType(bundle)) {
 				addHandler(bundle);
 			}
 			else {
 				if (log.isDebugEnabled())
 					log.debug("Bundle [" + OsgiStringUtils.nullSafeNameAndSymName(bundle)
 							+ "] declares namespace handlers but is not compatible with extender [" + extenderInfo
 							+ "]; ignoring...");
 			}
 
 		}
 		else {
 			// bundle declares only schemas, add it though the handlers might not be compatible...
 			if (hasSchemas)
 				addHandler(bundle);
 		}
 	}
 
 	private boolean hasCompatibleNamespaceType(Bundle bundle) {
 		try {
 			Class type = bundle.loadClass(NS_HANDLER_RESOLVER_CLASS_NAME);
 			return NamespaceHandlerResolver.class.equals(type);
 		}
 		catch (Throwable th) {
 			// if the interface is not wired, ignore the bundle
 			log.warn("Bundle " + OsgiStringUtils.nullSafeNameAndSymName(bundle) + " cannot see class ["
 					+ NS_HANDLER_RESOLVER_CLASS_NAME + "]; ignoring its namespace handlers");
 
 			return false;
 		}
 	}
 
 	/**
 	 * Add this bundle to those known to provide handler or schema mappings.
 	 * This method expects that the validity check (whatever that is) has been
 	 * already done.
 	 * 
 	 * @param bundle
 	 */
 	protected void addHandler(Bundle bundle) {
 		Assert.notNull(bundle);
 		if (log.isDebugEnabled()) {
 			log.debug("Adding namespace handler resolver for " + OsgiStringUtils.nullSafeNameAndSymName(bundle));
 		}
 
 		this.namespacePlugins.addHandler(bundle);
 	}
 
 	/**
 	 * Remove this bundle from the set of those known to provide handler or
 	 * schema mappings.
 	 * 
 	 * @param bundle
 	 */
 	public void maybeRemoveNameSpaceHandlerFor(Bundle bundle) {
 		Assert.notNull(bundle);
 		boolean removed = this.namespacePlugins.removeHandler(bundle);
 		if (removed && log.isDebugEnabled()) {
 			log.debug("Removed namespace handler resolver for " + OsgiStringUtils.nullSafeNameAndSymName(bundle));
 		}
 	}
 
 	/**
 	 * Register the NamespacePlugins instance as an Osgi Resolver service
 	 */
 	private void registerResolverServices() {
 		if (log.isDebugEnabled()) {
 			log.debug("Registering Spring NamespaceHandlerResolver and EntityResolver...");
 		}
 
 		nsResolverRegistration = context.registerService(new String[] { NamespaceHandlerResolver.class.getName() },
 			this.namespacePlugins, null);
 
 		enResolverRegistration = context.registerService(new String[] { EntityResolver.class.getName() },
 			this.namespacePlugins, null);
 
 	}
 
 	/**
 	 * Unregister the NamespaceHandler and EntityResolver service
 	 */
 	private void unregisterResolverService() {
 
 		boolean result = OsgiServiceUtils.unregisterService(nsResolverRegistration);
 		result = result || OsgiServiceUtils.unregisterService(enResolverRegistration);
 
 		if (result) {
 			if (log.isDebugEnabled())
 				log.debug("Unregistering Spring NamespaceHandler and EntityResolver service");
 		}
 
 		this.nsResolverRegistration = null;
 		this.enResolverRegistration = null;
 	}
 
 	/**
 	 * @return Returns the namespacePlugins.
 	 */
 	public NamespacePlugins getNamespacePlugins() {
 		return namespacePlugins;
 	}
 
 	//
 	// Lifecycle methods
 	//
 
 	public void afterPropertiesSet() {
 		registerResolverServices();
 	}
 
 	public void destroy() {
 		unregisterResolverService();
 		this.namespacePlugins.destroy();
 		this.namespacePlugins = null;
 	}
 
 }