/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.apache.myfaces.config;
  
  import java.lang.reflect.InvocationTargetException;
  import java.util.Map;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import javax.faces.component.UIViewRoot;
  import javax.faces.context.ExternalContext;
  import javax.faces.context.FacesContext;
  import javax.faces.event.PreDestroyCustomScopeEvent;
  import javax.faces.event.PreDestroyViewMapEvent;
  import javax.faces.event.ScopeContext;
  import javax.faces.event.SystemEvent;
  import javax.faces.event.SystemEventListener;
  import javax.servlet.ServletContext;
  
  import org.apache.myfaces.config.annotation.LifecycleProvider;
  import org.apache.myfaces.config.annotation.LifecycleProviderFactory;
  import org.apache.myfaces.context.servlet.StartupServletExternalContextImpl;
  
  /**
   * Destroyes managed beans with the current LifecycleProvider.
   * This guarantees the invocation of the @PreDestroy methods.
   * @author Jakob Korherr (latest modification by $Author: bommel $)
   * @version $Revision: 1187700 $ $Date: 2011-10-22 07:19:37 -0500 (Sat, 22 Oct 2011) $
   * @since 2.0
   */
  public class ManagedBeanDestroyer implements SystemEventListener
  {
      
      private static Logger log = Logger.getLogger(ManagedBeanDestroyer.class.getName());
      
      private RuntimeConfig _runtimeConfig;
      private LifecycleProvider _lifecycleProvider;
  
      /**
       * Creates the ManagedBeanDestroyer for the given RuntimeConfig
       * and LifecycleProvider.
       * 
       * @param lifecycleProvider
       * @param runtimeConfig
       */
      public ManagedBeanDestroyer(LifecycleProvider lifecycleProvider,
                                  RuntimeConfig runtimeConfig)
      {
          _lifecycleProvider = lifecycleProvider;
          _runtimeConfig = runtimeConfig;
      }
  
      public boolean isListenerForSource(Object source)
      {
          // source of PreDestroyCustomScopeEvent is ScopeContext
          // and source of PreDestroyViewMapEvent is UIViewRoot
          return (source instanceof ScopeContext) || (source instanceof UIViewRoot);
      }
  
      /**
       * Listens to PreDestroyCustomScopeEvent and PreDestroyViewMapEvent
       * and invokes destroy() for every managed bean in the associated scope.
       */
      public void processEvent(SystemEvent event)
      {
          Map<String, Object> scope = null;
          
          if (event instanceof PreDestroyViewMapEvent)
          {
              UIViewRoot viewRoot = (UIViewRoot) ((PreDestroyViewMapEvent) event).getComponent();
              scope = viewRoot.getViewMap(false);
              if (scope == null)
              {
                  // view map does not exist --> nothing to destroy
                  return;
              }
          }
          else if (event instanceof PreDestroyCustomScopeEvent)
          {
              ScopeContext scopeContext = ((PreDestroyCustomScopeEvent) event).getContext();
              scope = scopeContext.getScope();
          }
          else
         {
             // wrong event
             return;
         }
         
         for (String key : scope.keySet())
         {
             Object value = scope.get(key);
             this.destroy(key, value);
         }
     }
     
     /**
      * Checks if the given managed bean exists in the RuntimeConfig.
      * @param name
      * @return
      */
     public boolean isManagedBean(String name)
     {
         return (_runtimeConfig.getManagedBean(name) != null);
     }
     
     /**
      * Destroys the given managed bean.
      * @param name
      * @param instance
      */
     public void destroy(String name, Object instance)
     {
         if (instance != null && isManagedBean(name))
         {
             try
             {
                 _lifecycleProvider.destroyInstance(instance);
             } 
             catch (IllegalAccessException e)
             {
                 log.log(Level.SEVERE, "Could not access @PreDestroy method of managed bean " + name, e);
             } 
             catch (InvocationTargetException e)
             {
                 log.log(Level.SEVERE, "An Exception occured while invoking " +
                         "@PreDestroy method of managed bean " + name, e);
             }
         }
     }
 
 }