/*
    * 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 javax.faces.event;
  
  import javax.el.ELContext;
  import javax.el.ELException;
  import javax.el.ExpressionFactory;
  import javax.el.MethodExpression;
  import javax.el.MethodNotFoundException;
  import javax.faces.component.StateHolder;
  import javax.faces.context.FacesContext;
  
  /**
   * See Javadoc of <a href="https://javaserverfaces.dev.java.net/nonav/docs/2.0/javadocs/javax/faces/event/
   * MethodExpressionValueChangeListener.html">JSF Specification</a>
   * 
   * @author Stan Silvert
   * @author Jakob Korherr
   */
  public class MethodExpressionValueChangeListener implements ValueChangeListener, StateHolder
  {
  
      private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
      private static final Object[] EMPTY_PARAMS = new Object[0];
      
      private MethodExpression methodExpressionOneArg;
      private MethodExpression methodExpressionZeroArg;
      private boolean isTransient = false;
  
      /** Creates a new instance of MethodExpressionValueChangeListener */
      public MethodExpressionValueChangeListener()
      {
          // constructor for state-saving 
      }
  
      public MethodExpressionValueChangeListener(MethodExpression methodExpressionOneArg)
      {
          this.methodExpressionOneArg = methodExpressionOneArg;
          
          _createZeroArgsMethodExpression(methodExpressionOneArg); 
      }
  
      public MethodExpressionValueChangeListener(MethodExpression methodExpressionOneArg,
                                                 MethodExpression methodExpressionZeroArg)
      {
          this.methodExpressionOneArg = methodExpressionOneArg;
          if (methodExpressionZeroArg != null) 
          {
              this.methodExpressionZeroArg = methodExpressionZeroArg;
          }
          else
          {
              _createZeroArgsMethodExpression(methodExpressionOneArg);
          }
      }
  
      public void processValueChange(ValueChangeEvent event) throws AbortProcessingException
      {
          try
          {
              try
              {
                  // call to the one argument MethodExpression
                  Object[] params = new Object[] { event };
                  methodExpressionOneArg.invoke(getElContext(), params);
              }
              catch (MethodNotFoundException mnfe)
              {
                  // call to the zero argument MethodExpression
                  methodExpressionZeroArg.invoke(getElContext(), EMPTY_PARAMS);
              }
          }
          catch (ELException e)
          {
              // "... If that fails for any reason, throw an AbortProcessingException,
              // including the cause of the failure ..."
              // -= Leonardo Uribe =- after discussing this topic on MYFACES-3199, the conclusion is the part is an advice
              // for the developer implementing a listener in a method expressions that could be wrapped by this class.
              // The spec wording is poor but, to keep this coherently with ExceptionHandler API,
              // the spec and code on UIViewRoot we need:
              // 2a) "exception is instance of APE or any of the causes of the exception are an APE, 
              // DON'T publish ExceptionQueuedEvent and terminate processing for current event".
              // 2b) for any other exception publish ExceptionQueuedEvent and continue broadcast processing.
             Throwable cause = e.getCause();
             AbortProcessingException ape = null;
             if (cause != null)
             {
                 do
                 {
                     if (cause != null && cause instanceof AbortProcessingException)
                     {
                         ape = (AbortProcessingException) cause;
                         break;
                     }
                     cause = cause.getCause();
                 }
                 while (cause != null);
             }
             
             if (ape != null)
             {
                 // 2a) "exception is instance of APE or any of the causes of the exception are an APE, 
                 // DON'T publish ExceptionQueuedEvent and terminate processing for current event".
                 // To do this throw an AbortProcessingException here, later on UIViewRoot.broadcastAll,
                 // this exception will be received and stored to handle later.
                 throw ape;
             }
             //for any other exception publish ExceptionQueuedEvent and continue broadcast processing.
             throw e;
             //Throwable cause = e.getCause();
             //if (cause == null)
             //{
             //    cause = e;
             //}
             //if (cause instanceof AbortProcessingException)
             //{
             //    throw (AbortProcessingException) cause;
             //}
             //else
             //{
             //    throw new AbortProcessingException(cause);
             //}
         }
     }
 
     public void restoreState(FacesContext context, Object state)
     {
         methodExpressionOneArg = (MethodExpression) ((Object[]) state)[0];
         methodExpressionZeroArg = (MethodExpression) ((Object[]) state)[1];
     }
 
     public Object saveState(FacesContext context)
     {
         return new Object[] {methodExpressionOneArg, methodExpressionZeroArg};
     }
 
     public void setTransient(boolean newTransientValue)
     {
         isTransient = newTransientValue;
     }
 
     public boolean isTransient()
     {
         return isTransient;
     }
     
     private ELContext getElContext()
     {
         return getFacesContext().getELContext();
     }
     
     private FacesContext getFacesContext()
     {
         return FacesContext.getCurrentInstance();
     }
     
     /**
      * Creates a {@link MethodExpression} with no params and with the same Expression as 
      * param <code>methodExpression</code>
      * <b>WARNING!</b> This method creates new {@link MethodExpression} with expressionFactory.createMethodExpression.
      * That means is not decorating MethodExpression passed as parameter -
      * support for EL VariableMapper will not be available!
      * This is a problem when using facelets and <ui:decorate/> with EL params (see MYFACES-2541 for details).
      */
     private void _createZeroArgsMethodExpression(MethodExpression methodExpression)
     {
         ExpressionFactory expressionFactory = getFacesContext().getApplication().getExpressionFactory();
 
         this.methodExpressionZeroArg = expressionFactory.createMethodExpression(getElContext(), 
                   methodExpression.getExpressionString(), Void.class, EMPTY_CLASS_ARRAY);
     }
 
 }