/*
    * 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.webapp;
  
  import java.util.Enumeration;
  import javax.faces.context.ExceptionHandler;
  import javax.faces.context.ExternalContext;
  import javax.faces.context.FacesContext;
  
  import javax.servlet.ServletContext;
  import javax.servlet.ServletContextAttributeEvent;
  import javax.servlet.ServletContextAttributeListener;
  import javax.servlet.ServletContextEvent;
  import javax.servlet.ServletContextListener;
  import javax.servlet.ServletRequest;
  import javax.servlet.ServletRequestAttributeEvent;
  import javax.servlet.ServletRequestAttributeListener;
  import javax.servlet.ServletRequestEvent;
  import javax.servlet.ServletRequestListener;
  import javax.servlet.http.HttpSessionAttributeListener;
  import javax.servlet.http.HttpSessionBindingEvent;
  import javax.servlet.http.HttpSessionEvent;
  import javax.servlet.http.HttpSessionListener;
  
  import org.apache.myfaces.config.ManagedBeanDestroyer;
  import org.apache.myfaces.context.ReleaseableExternalContext;
  import org.apache.myfaces.context.servlet.StartupFacesContextImpl;
  import org.apache.myfaces.context.servlet.StartupServletExternalContextImpl;
  import org.apache.myfaces.shared.context.ExceptionHandlerImpl;
  import org.apache.myfaces.spi.ViewScopeProvider;
  
  /**
   * Listens to
   *   - removing, replacing of attributes in context, session and request
   *   - destroying of context, session and request
   * for the ManagedBeanDestroyer to assure right destruction of managed beans in those scopes.
   * 
   * This listener is not registered in a tld or web.xml, but will be called by StartupServletContextListener.
   * 
   * @author Jakob Korherr (latest modification by $Author$)
   * @version $Revision$ $Date$
   * @since 2.0
   */
  public class ManagedBeanDestroyerListener implements 
          HttpSessionAttributeListener, HttpSessionListener,
          ServletContextListener, ServletContextAttributeListener,
          ServletRequestListener, ServletRequestAttributeListener
  {
      /**
       * The instance of the ManagedBeanDestroyerListener created by StartupServletContextListener
       * is stored under this key in the ApplicationMap.
       */
      public static final String APPLICATION_MAP_KEY = ManagedBeanDestroyerListener.class.getName();
  
      private ManagedBeanDestroyer _destroyer = null;
      private ViewScopeProvider _viewScopeHandler = null;
      
      @Override
      public void contextInitialized(ServletContextEvent event)
      {
  
      }
      
      @Override
      public void contextDestroyed(ServletContextEvent event)
      {
          if (_destroyer != null)
          {
              ServletContext ctx = event.getServletContext();
              Enumeration<String> attributes = ctx.getAttributeNames();
              if (!attributes.hasMoreElements())
              {
                  // nothing to do
                  return;
              }
  
              while (attributes.hasMoreElements())
              {
                  String name = attributes.nextElement();
                  Object value = ctx.getAttribute(name);
                  _destroyer.destroy(name, value);
              }
          }
     }
 
     /**
      * Sets the ManagedBeanDestroyer instance to use.
      *  
      * @param destroyer
      */
     public void setManagedBeanDestroyer(ManagedBeanDestroyer destroyer)
     {
         _destroyer = destroyer;
     }
     
     public void setViewScopeHandler(ViewScopeProvider listener)
     {
         _viewScopeHandler = listener;
     }
 
     /* Session related methods ***********************************************/
     @Override
     public void attributeAdded(HttpSessionBindingEvent event)
     {
         // noop
     }
 
     @Override
     public void attributeRemoved(HttpSessionBindingEvent event)
     {
         if (_destroyer != null)
         {
             _destroyer.destroy(event.getName(), event.getValue());
         }
     }
 
     @Override
     public void attributeReplaced(HttpSessionBindingEvent event)
     {
         if (_destroyer != null)
         {
             _destroyer.destroy(event.getName(), event.getValue());
         }
     }
 
     @Override
     public void sessionCreated(HttpSessionEvent event)
     {
         // noop
     }
 
     @Override
     public void sessionDestroyed(HttpSessionEvent event)
     {
         // MYFACES-3040 @PreDestroy Has Called 2 times
         // attributeRemoved receives the event too, so it does not 
         // have sense to handle it here. Unfortunately, it is not possible to 
         // handle it first and then on attributeRemoved, so the best bet is
         // let the code in just one place.
         /*
         if (_destroyer != null)
         {
             HttpSession session = event.getSession();
             Enumeration<String> attributes = session.getAttributeNames();
             if (!attributes.hasMoreElements())
             {
                 // nothing to do
                 return;
             }
 
             while (attributes.hasMoreElements())
             {
                 String name = attributes.nextElement();
                 Object value = session.getAttribute(name);
                 _destroyer.destroy(name, value);
             }
         }*/
         
         // If we don't propagate this event, CDI will do for us but outside JSF control
         // so when @PreDestroy methods are called there will not be an active FacesContext.
         // The trick here is ensure clean the affected scopes to avoid duplicates.
         // Remember cdi session scope is different from jsf session scope, because in
         // jsf case the beans are stored under a session attribute, so it has the problem
         // with attributeRemoved, but on cdi a wrapper is used instead, avoiding the problem.
         if (_viewScopeHandler != null)
         {
             FacesContext facesContext = FacesContext.getCurrentInstance();
             if (facesContext != null)
             {
                 _viewScopeHandler.onSessionDestroyed();
             }
             else
             {
                 // In case no FacesContext is available, we are on session invalidation
                 // through timeout. In that case, create a dummy FacesContext for this one
                 // like the one used in startup or shutdown and invoke the destroy method.
                 try
                 {
                     ServletContext servletContext = event.getSession().getServletContext();
                     ExternalContext externalContext = new StartupServletExternalContextImpl(servletContext, false);
                     ((StartupServletExternalContextImpl)externalContext).setSession(event.getSession());
                     ExceptionHandler exceptionHandler = new ExceptionHandlerImpl();
                     facesContext = new StartupFacesContextImpl(externalContext, 
                             (ReleaseableExternalContext) externalContext, exceptionHandler, false);
                     _viewScopeHandler.onSessionDestroyed();
                 }
                 finally
                 {
                     facesContext.release();
                 }
             }
         }
     }
     
     /* Context related methods ***********************************************/
     @Override
     public void attributeAdded(ServletContextAttributeEvent event)
     {
         // noop
     }
 
     @Override
     public void attributeRemoved(ServletContextAttributeEvent event)
     {
         if (_destroyer != null)
         {
             _destroyer.destroy(event.getName(), event.getValue());
         }
     }
 
     @Override
     public void attributeReplaced(ServletContextAttributeEvent event)
     {
         if (_destroyer != null)
         {
             _destroyer.destroy(event.getName(), event.getValue());
         }
     }
     
     /* Request related methods ***********************************************/
     @Override
     public void attributeAdded(ServletRequestAttributeEvent event)
     {
         // noop
     }
 
     @Override
     public void attributeRemoved(ServletRequestAttributeEvent event)
     {
         if (_destroyer != null)
         {
             _destroyer.destroy(event.getName(), event.getValue());
         }
     }
 
     @Override
     public void attributeReplaced(ServletRequestAttributeEvent event)
     {
         if (_destroyer != null)
         {
             _destroyer.destroy(event.getName(), event.getValue());
         }
     }
 
     @Override
     public void requestInitialized(ServletRequestEvent event)
     {
         // noop
     }
     
     @Override
     public void requestDestroyed(ServletRequestEvent event)
     {
         if (_destroyer != null)
         {
             ServletRequest request = event.getServletRequest();
             Enumeration<String> attributes = request.getAttributeNames();
             if (!attributes.hasMoreElements())
             {
                 // nothing to do
                 return;
             }
             
             while (attributes.hasMoreElements())
             {
                 String name = attributes.nextElement();
                 Object value = request.getAttribute(name);
                 _destroyer.destroy(name, value);
             }
         }
     }
 
 }