/*
    * 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.shared.context;
  
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.Queue;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import javax.el.ELException;
  import javax.faces.FacesException;
  import javax.faces.context.ExceptionHandler;
  import javax.faces.event.AbortProcessingException;
  import javax.faces.event.ExceptionQueuedEvent;
  import javax.faces.event.ExceptionQueuedEventContext;
  import javax.faces.event.SystemEvent;
  
  /**
   * DOCUMENT ME!
   * 
   * @since 2.0
   */
  public class ExceptionHandlerImpl extends ExceptionHandler
  {
      /*
       * PLEASE NOTE!!!
       * javax.faces.webapp.PreJsf2ExceptionHandlerFactory uses most parts of this implementation
       * for its private static inner class, only the handle method differs a bit.
       * Thus, any changes made here should also be applied to PreJsf2ExceptionHandlerFactory
       * in the right way (you can copy everything except handle(), this method needs special treatment).
       */
      
      private static final Logger log = Logger.getLogger(ExceptionHandlerImpl.class.getName());
      
      private Queue<ExceptionQueuedEvent> handled;
      private Queue<ExceptionQueuedEvent> unhandled;
      private ExceptionQueuedEvent handledAndThrown;
  
      public ExceptionHandlerImpl()
      {
          
      }
      
      /**
       * {@inheritDoc}
       */
      @Override
      public ExceptionQueuedEvent getHandledExceptionQueuedEvent()
      {
          return handledAndThrown;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public Iterable<ExceptionQueuedEvent> getHandledExceptionQueuedEvents()
      {
          return handled == null ? Collections.<ExceptionQueuedEvent>emptyList() : handled;
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public Throwable getRootCause(Throwable t)
      {
          if (t == null)
          {
              throw new NullPointerException("t");
          }
          
          while (t != null)
          {
              Class<?> clazz = t.getClass();
              if (!clazz.equals(FacesException.class) && !clazz.equals(ELException.class))
              {
                  return t;
              }
              
              t = t.getCause();
          }
         
         return null;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public Iterable<ExceptionQueuedEvent> getUnhandledExceptionQueuedEvents()
     {
         return unhandled == null ? Collections.<ExceptionQueuedEvent>emptyList() : unhandled;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void handle() throws FacesException
     {
         if (unhandled != null && !unhandled.isEmpty())
         {
             if (handled == null)
             {
                 handled = new LinkedList<ExceptionQueuedEvent>();
             }
             
             FacesException toThrow = null;
             
             do
             {
                 // For each ExceptionEvent in the list
                 
                 // get the event to handle
                 ExceptionQueuedEvent event = unhandled.peek();
                 try
                 {
                     // call its getContext() method
                     ExceptionQueuedEventContext context = event.getContext();
                     
                     // and call getException() on the returned result
                     Throwable exception = context.getException();
                     
                     // Upon encountering the first such Exception that is not an instance of
                     // javax.faces.event.AbortProcessingException
                     if (!shouldSkip(exception))
                     {
                         // set handledAndThrown so that getHandledExceptionQueuedEvent() returns this event
                         handledAndThrown = event;
                         
                         // Re-wrap toThrow in a ServletException or (PortletException, if in a portlet environment) 
                         // and throw it
                         // FIXME: The spec says to NOT use a FacesException to propagate the exception, but I see
                         //        no other way as ServletException is not a RuntimeException
                         toThrow = wrap(getRethrownException(exception));
                         break;
                     }
                     else
                     {
                         // Testing mojarra it logs a message and the exception
                         // however, this behaviour is not mentioned in the spec
                         log.log(Level.SEVERE, exception.getClass().getName() + " occured while processing " +
                                 (context.inBeforePhase() ? "beforePhase() of " : 
                                         (context.inAfterPhase() ? "afterPhase() of " : "")) + 
                                 "phase " + context.getPhaseId() + ": " +
                                 "UIComponent-ClientId=" + 
                                 (context.getComponent() != null ? 
                                         context.getComponent().getClientId(context.getContext()) : "") + ", " +
                                 "Message=" + exception.getMessage());
                         
                         log.log(Level.SEVERE, exception.getMessage(), exception);
                         
                     }
                 }
                 catch (Throwable t)
                 {
                     // A FacesException must be thrown if a problem occurs while performing
                     // the algorithm to handle the exception
                     throw new FacesException("Could not perform the algorithm to handle the Exception", t);
                 }
                 finally
                 {
                     // if we will throw the Exception or if we just logged it,
                     // we handled it in either way --> add to handled
                     handled.add(event);
                     unhandled.remove(event);
                 }
             } while (!unhandled.isEmpty());
             
             // do we have to throw an Exception?
             if (toThrow != null)
             {
                 throw toThrow;
             }
         }
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean isListenerForSource(Object source)
     {
         return source instanceof ExceptionQueuedEventContext;
     }
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void processEvent(SystemEvent exceptionQueuedEvent) throws AbortProcessingException
     {
         if (unhandled == null)
         {
             unhandled = new LinkedList<ExceptionQueuedEvent>();
         }
         
         unhandled.add((ExceptionQueuedEvent)exceptionQueuedEvent);
     }
     
     protected Throwable getRethrownException(Throwable exception)
     {
         // Let toRethrow be either the result of calling getRootCause() on the Exception, 
         // or the Exception itself, whichever is non-null
         Throwable toRethrow = getRootCause(exception);
         if (toRethrow == null)
         {
             toRethrow = exception;
         }
         
         return toRethrow;
     }
     
     protected FacesException wrap(Throwable exception)
     {
         if (exception instanceof FacesException)
         {
             return (FacesException) exception;
         }
         return new FacesException(exception);
     }
     
     protected boolean shouldSkip(Throwable exception)
     {
         return exception instanceof AbortProcessingException;
     }
 }