/*
    * 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.view.facelets.tag.jsf.core;
  
  import java.io.IOException;
  import java.io.Serializable;
  import java.util.Collection;
  import java.util.Iterator;
  
  import javax.el.ELContext;
  import javax.el.ELException;
  import javax.el.MethodExpression;
  import javax.el.MethodNotFoundException;
  import javax.faces.FacesException;
  import javax.faces.component.PartialStateHolder;
  import javax.faces.component.UIComponent;
  import javax.faces.component.UIViewRoot;
  import javax.faces.context.FacesContext;
  import javax.faces.event.ComponentSystemEvent;
  import javax.faces.event.ComponentSystemEventListener;
  import javax.faces.event.PostAddToViewEvent;
  import javax.faces.event.PreRenderViewEvent;
  import javax.faces.view.facelets.ComponentHandler;
  import javax.faces.view.facelets.FaceletContext;
  import javax.faces.view.facelets.FaceletException;
  import javax.faces.view.facelets.TagAttribute;
  import javax.faces.view.facelets.TagAttributeException;
  import javax.faces.view.facelets.TagConfig;
  import javax.faces.view.facelets.TagHandler;
  
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFFaceletAttribute;
  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFFaceletTag;
  import org.apache.myfaces.config.RuntimeConfig;
  import org.apache.myfaces.view.facelets.FaceletCompositionContext;
  import org.apache.myfaces.view.facelets.FaceletViewDeclarationLanguage;
  import org.apache.myfaces.view.facelets.el.CompositeComponentELUtils;
  import org.apache.myfaces.view.facelets.tag.jsf.ComponentSupport;
  import org.apache.myfaces.view.facelets.util.ReflectionUtil;
  
  /**
   * Registers a listener for a given system event class on the UIComponent associated with this tag.
   */
  @JSFFaceletTag(
          name = "f:event",
          bodyContent = "empty")
  public final class EventHandler extends TagHandler
  {
      
      private static final Class<?>[] COMPONENT_SYSTEM_EVENT_PARAMETER = new Class<?>[] { ComponentSystemEvent.class };
      private static final Class<?>[] EMPTY_CLASS_ARRAY = new Class<?>[0];
      
      @JSFFaceletAttribute(name="listener",
              className="javax.el.MethodExpression",
              deferredMethodSignature=
              "public void listener(javax.faces.event.ComponentSystemEvent evt) "
              + "throws javax.faces.event.AbortProcessingException")
      private TagAttribute listener;
      
      @JSFFaceletAttribute(name="type",
              className="javax.el.ValueExpression",
              deferredValueType="java.lang.String")
      private TagAttribute type;
      
      private boolean listenerIsCompositeComponentME;
      
      public EventHandler (TagConfig tagConfig)
      {
          super (tagConfig);
          
          listener = getRequiredAttribute("listener");
          if (!listener.isLiteral())
          {
              listenerIsCompositeComponentME
                      = CompositeComponentELUtils.isCompositeComponentExpression(listener.getValue());
          }
          else
          {
              listenerIsCompositeComponentME = false;
          }
          type = getRequiredAttribute("type");
      }
      
      public void apply (FaceletContext ctx, UIComponent parent)
             throws ELException, FacesException, FaceletException, IOException
     {
         //Apply only if we are creating a new component
         if (!ComponentHandler.isNew(parent))
         {
             return;
         }
         if (parent instanceof UIViewRoot)
         {
             if (FaceletCompositionContext.getCurrentInstance(ctx).isRefreshingTransientBuild())
             {
                 return;
             }
             else if (!FaceletViewDeclarationLanguage.isBuildingViewMetadata(ctx.getFacesContext()) &&
                     UIViewRoot.METADATA_FACET_NAME.equals((String) parent.getAttributes().get(FacetHandler.KEY)))
             {
                 // Already processed when the view metadata was created
                 return;
             }
         }
         
         Class<? extends ComponentSystemEvent> eventClass = getEventClass(ctx);
         
         // Note: The listener attribute can now also take a zero-argument MethodExpression,
         // thus we need two different MethodExpressions (see MYFACES-2503 for details).
         MethodExpression methodExpOneArg 
                 = listener.getMethodExpression(ctx, void.class, COMPONENT_SYSTEM_EVENT_PARAMETER);
         MethodExpression methodExpZeroArg
                 = listener.getMethodExpression(ctx, void.class, EMPTY_CLASS_ARRAY);
         
         if (eventClass == PreRenderViewEvent.class)
         {
             // ensure ViewRoot for PreRenderViewEvent
             UIViewRoot viewRoot = ComponentSupport.getViewRoot(ctx, parent);
             if (listenerIsCompositeComponentME)
             {
                 // Subscribe after the view is built, so we can calculate a
                 // findComponent valid expression, and then use it to
                 // put the expression in context.
                 UIComponent parentCompositeComponent
                         = FaceletCompositionContext.getCurrentInstance(ctx).getCompositeComponentFromStack();
                 parentCompositeComponent.subscribeToEvent(PostAddToViewEvent.class, 
                         new SubscribeEventListener(eventClass, methodExpOneArg, methodExpZeroArg,
                                                    (eventClass == PreRenderViewEvent.class) ? null : parent));
             }
             else
             {
                 viewRoot.subscribeToEvent(eventClass, new Listener(methodExpOneArg, methodExpZeroArg));
             }
         }
         else
         {
             // Simply register the event on the component.
             parent.subscribeToEvent(eventClass, new Listener(methodExpOneArg, methodExpZeroArg));
         }
     }
     
     /**
      * Gets the event class defined by the tag (either in the "name" or "type" attribute).
      * 
      * @param context the Facelet context
      * @return a Class containing the event class defined by the tag.
      */
     
     @SuppressWarnings("unchecked")
     private Class<? extends ComponentSystemEvent> getEventClass (FaceletContext context)
     {
         Class<?> eventClass = null;
         String value = null;
         if (type.isLiteral())
         {
             value = type.getValue();
         }
         else
         {
             value = (String) type.getValueExpression (context, String.class).
                 getValue (context.getFacesContext().getELContext());
         }
         
         Collection<Class<? extends ComponentSystemEvent>> events;
         
         // We can look up the event class by name in the NamedEventManager.
         
         events = RuntimeConfig.getCurrentInstance(
                 context.getFacesContext().getExternalContext()).
                     getNamedEventManager().getNamedEvent(value);
         
         if (events == null)
         {
             try
             {
                 eventClass = ReflectionUtil.forName (value);
             }
             catch (Throwable e)
             {
                 throw new TagAttributeException (type, "Couldn't create event class", e);
             }
         }
         else if (events.size() > 1)
         {
             StringBuilder classNames = new StringBuilder ("[");
             Iterator<Class<? extends ComponentSystemEvent>> eventIterator = events.iterator();
             
             // TODO: The spec is somewhat vague, but I think we're supposed to throw an exception
             // here.  The @NamedEvent javadocs say that if a short name is registered to more than one
             // event class that we must throw an exception listing the short name and the classes in
             // the list _when the application makes reference to it_.  I believe processing this tag
             // qualifies as the application "making reference" to the short name.  Why the exception
             // isn't thrown when processing the @NamedEvent annotation, I don't know.  Perhaps follow
             // up with the EG to see if this is correct.
             
             while (eventIterator.hasNext())
             {
                 classNames.append (eventIterator.next().getName());
                 
                 if (eventIterator.hasNext())
                 {
                     classNames.append (", ");
                 }
                 else
                 {
                     classNames.append ("]");
                 }
             }
             
             throw new FacesException ("The event name '" + value + "' is mapped to more than one " +
                 " event class: " + classNames.toString());
         }
         else
         {
             eventClass = events.iterator().next();
         }
         
         if (!ComponentSystemEvent.class.isAssignableFrom (eventClass))
         {
             throw new TagAttributeException (type, "Event class " + eventClass.getName() +
                 " is not of type javax.faces.event.ComponentSystemEvent");
         }
         
         return (Class<? extends ComponentSystemEvent>) eventClass;
     }
     
     public static class Listener implements ComponentSystemEventListener, Serializable 
     {
 
         private static final long serialVersionUID = 7318240026355007052L;
         
         private MethodExpression methodExpOneArg;
         private MethodExpression methodExpZeroArg;
         
         public Listener()
         {
             super();
         }
 
         /**
          * Note: The listener attribute can now also take a zero-argument MethodExpression,
          * thus we need two different MethodExpressions (see MYFACES-2503 for details).
          * @param methodExpOneArg
          * @param methodExpZeroArg
          */
         private Listener(MethodExpression methodExpOneArg, MethodExpression methodExpZeroArg)
         {
             this.methodExpOneArg = methodExpOneArg;
             this.methodExpZeroArg = methodExpZeroArg;
         }
         
         public void processEvent(ComponentSystemEvent event)
         {
             ELContext elContext = FacesContext.getCurrentInstance().getELContext();
             try
             {
                 // first try to invoke the MethodExpression with one argument
                 this.methodExpOneArg.invoke(elContext, new Object[] { event });
             }
             catch (MethodNotFoundException mnfeOneArg)
             {
                 try
                 {
                     // if that fails try to invoke the MethodExpression with zero arguments
                     this.methodExpZeroArg.invoke(elContext, new Object[0]);
                 }
                 catch (MethodNotFoundException mnfeZeroArg)
                 {
                     // if that fails too rethrow the original MethodNotFoundException
                     throw mnfeOneArg;
                 }
             }
         }
     }
     
     public static class CompositeComponentRelativeListener  implements ComponentSystemEventListener, Serializable 
     {
         /**
          * 
          */
         private static final long serialVersionUID = 3822330995358746099L;
         
         private String _compositeComponentExpression;
         private MethodExpression methodExpOneArg;
         private MethodExpression methodExpZeroArg;
         
         public CompositeComponentRelativeListener()
         {
             super();
         }
         
         public CompositeComponentRelativeListener(MethodExpression methodExpOneArg, 
                                 MethodExpression methodExpZeroArg, 
                                 String compositeComponentExpression)
         {
             this.methodExpOneArg = methodExpOneArg;
             this.methodExpZeroArg = methodExpZeroArg;
             this._compositeComponentExpression = compositeComponentExpression;
         }
         
         public void processEvent(ComponentSystemEvent event)
         {
             FacesContext facesContext = FacesContext.getCurrentInstance();
             UIComponent cc = facesContext.getViewRoot().findComponent(_compositeComponentExpression);
             
             if (cc != null)
             {
                 pushAllComponentsIntoStack(facesContext, cc);
                 cc.pushComponentToEL(facesContext, cc);
                 try
                 {
                     ELContext elContext = facesContext.getELContext();
                     try
                     {
                         // first try to invoke the MethodExpression with one argument
                         this.methodExpOneArg.invoke(elContext, new Object[] { event });
                     }
                     catch (MethodNotFoundException mnfeOneArg)
                     {
                         try
                         {
                             // if that fails try to invoke the MethodExpression with zero arguments
                             this.methodExpZeroArg.invoke(elContext, new Object[0]);
                         }
                         catch (MethodNotFoundException mnfeZeroArg)
                         {
                             // if that fails too rethrow the original MethodNotFoundException
                             throw mnfeOneArg;
                         }
                     }
                 }
                 finally
                 {
                     popAllComponentsIntoStack(facesContext, cc);
                 }
             }
             else
             {
                 throw new NullPointerException("Composite Component associated with expression cannot be found");
             }
         }
         
         private void pushAllComponentsIntoStack(FacesContext facesContext, UIComponent component)
         {
             UIComponent parent = component.getParent();
             if (parent != null)
             {
                 pushAllComponentsIntoStack(facesContext, parent);
             }
             component.pushComponentToEL(facesContext, component);
         }
         
         private void popAllComponentsIntoStack(FacesContext facesContext, UIComponent component)
         {
             UIComponent parent = component.getParent();
             component.popComponentFromEL(facesContext);
             if (parent != null)
             {
                 popAllComponentsIntoStack(facesContext, parent);
             }
         }
     }
     
     public static final class SubscribeEventListener implements ComponentSystemEventListener, PartialStateHolder
     {
         private MethodExpression methodExpOneArg;
         private MethodExpression methodExpZeroArg;
         private Class<? extends ComponentSystemEvent> eventClass;
         private UIComponent _targetComponent;
         private String _targetFindComponentExpression;
     
         private boolean markInitialState;
 
         public SubscribeEventListener()
         {
         }
         
         public SubscribeEventListener(
                 Class<? extends ComponentSystemEvent> eventClass,
                 MethodExpression methodExpOneArg, 
                 MethodExpression methodExpZeroArg,
                 UIComponent targetComponent)
         {
             //_listener = listener;
             this.eventClass = eventClass;
             this.methodExpOneArg = methodExpOneArg;
             this.methodExpZeroArg = methodExpZeroArg;
             this._targetComponent = targetComponent;
         }
         
         public void processEvent(ComponentSystemEvent event)
         {
             UIComponent parentCompositeComponent = event.getComponent();
             FacesContext facesContext = FacesContext.getCurrentInstance();
             //Calculate a findComponent expression to locate the right instance so PreRenderViewEvent could be called
             String findComponentExpression
                     = ComponentSupport.getFindComponentExpression(facesContext, parentCompositeComponent);
             
             //Note in practice this is only used for PreRenderViewEvent, but in the future it could be more events that
             //require this hack.
             if (eventClass == PreRenderViewEvent.class)
             {
                 // ensure ViewRoot for PreRenderViewEvent
                 UIViewRoot viewRoot = facesContext.getViewRoot();
                 viewRoot.subscribeToEvent(eventClass, new CompositeComponentRelativeListener(methodExpOneArg,
                                                                         methodExpZeroArg, findComponentExpression));
             }
             else
             {
                 if (_targetComponent == null)
                 {
                     if (_targetFindComponentExpression.startsWith(findComponentExpression) )
                     {
                         _targetComponent = ComponentSupport.findComponentChildOrFacetFrom(
                                 facesContext, parentCompositeComponent, 
                                 _targetFindComponentExpression.substring(findComponentExpression.length()));
                     }
                     else
                     {
                         _targetComponent = facesContext.getViewRoot().findComponent(_targetFindComponentExpression);
                     }
                 }
                 
                 _targetComponent.subscribeToEvent(eventClass,
                         new CompositeComponentRelativeListener(methodExpOneArg, methodExpZeroArg,
                                                                findComponentExpression));
             }
         }
         
         public Object saveState(FacesContext context)
         {
             if (!initialStateMarked())
             {
                 Object[] values = new Object[4];
                 values[0] = (String) ( (_targetComponent != null && _targetFindComponentExpression == null) ? 
                                             ComponentSupport.getFindComponentExpression(context, _targetComponent) : 
                                             _targetFindComponentExpression );
                 values[1] = eventClass;
                 values[2] = methodExpZeroArg;
                 values[3] = methodExpOneArg;
                 return values;
             }
             // If the listener was marked, no need to save anything, because 
             // this object is immutable after that.
             return null;
         }
 
         public void restoreState(FacesContext context, Object state)
         {
             if (state == null)
             {
                 return;
             }
             Object[] values = (Object[])state;
             _targetFindComponentExpression = (String) values[0];
             eventClass = (Class) values[1];
             methodExpZeroArg = (MethodExpression) values[2];
             methodExpOneArg = (MethodExpression) values[3];
         }
 
         public boolean isTransient()
         {
             return false;
         }
 
         public void setTransient(boolean newTransientValue)
         {
             // no-op as listener is transient
         }
         
         public void clearInitialState()
         {
             markInitialState = false;
         }
 
         public boolean initialStateMarked()
         {
             return markInitialState;
         }
 
         public void markInitialState()
         {
             markInitialState = true;
         }
     }
 }