/*
    * 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.util.Collection;
  import java.util.List;
  import java.util.Map;
  
  import javax.el.MethodExpression;
  import javax.faces.component.PartialStateHolder;
  import javax.faces.component.UIComponent;
  import javax.faces.component.UniqueIdVendor;
  import javax.faces.component.behavior.AjaxBehavior;
  import javax.faces.component.behavior.ClientBehavior;
  import javax.faces.component.behavior.ClientBehaviorHolder;
  import javax.faces.context.FacesContext;
  import javax.faces.event.AbortProcessingException;
  import javax.faces.event.AjaxBehaviorEvent;
  import javax.faces.event.AjaxBehaviorListener;
  import javax.faces.view.BehaviorHolderAttachedObjectHandler;
  import javax.faces.view.facelets.ComponentHandler;
  import javax.faces.view.facelets.FaceletContext;
  import javax.faces.view.facelets.FaceletHandler;
  import javax.faces.view.facelets.TagAttribute;
  import javax.faces.view.facelets.TagAttributeException;
  import javax.faces.view.facelets.TagConfig;
  import javax.faces.view.facelets.TagException;
  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.shared.renderkit.JSFAttr;
  import org.apache.myfaces.shared.renderkit.html.util.ResourceUtils;
  import org.apache.myfaces.view.facelets.AbstractFaceletContext;
  import org.apache.myfaces.view.facelets.FaceletCompositionContext;
  import org.apache.myfaces.view.facelets.tag.TagHandlerUtils;
  import org.apache.myfaces.view.facelets.tag.composite.InsertChildrenHandler;
  import org.apache.myfaces.view.facelets.tag.jsf.ComponentSupport;
  import org.apache.myfaces.view.facelets.tag.ui.DecorateHandler;
  import org.apache.myfaces.view.facelets.tag.ui.IncludeHandler;
  import org.apache.myfaces.view.facelets.tag.ui.InsertHandler;
  
  /**
   * This tag creates an instance of AjaxBehavior, and associates it with the nearest 
   * parent UIComponent that implements ClientBehaviorHolder interface. This tag can
   * be used on single or composite components.
   * <p>
   * Unless otherwise specified, all attributes accept static values or EL expressions.
   * </p>
   * <p>
   * According to the documentation, the tag handler implementing this tag should meet
   * the following conditions:  
   * </p>
   * <ul>
   * <li>Since this tag attach objects to UIComponent instances, and those instances 
   * implements Behavior interface, this component should implement 
   * BehaviorHolderAttachedObjectHandler interface.</li>
   * <li>f:ajax does not support binding property. In theory we should do something similar
   * to f:convertDateTime tag does: extends from ConverterHandler and override setAttributes
   * method, but in this case BehaviorTagHandlerDelegate has binding property defined, so
   * if we extend from BehaviorHandler we add binding support to f:ajax.</li>
   * <li>This tag works as a attached object handler, but note on the api there is no component
   * to define a target for a behavior. See comment inside apply() method.</li>
   * </ul>
   * @author Leonardo Uribe (latest modification by $Author: struberg $)
   * @version $Revision: 1194861 $ $Date: 2011-10-29 05:02:34 -0500 (Sat, 29 Oct 2011) $
   */
  @JSFFaceletTag(name = "f:ajax")
  public class AjaxHandler extends TagHandler implements
          BehaviorHolderAttachedObjectHandler
  {
  
      public final static Class<?>[] AJAX_BEHAVIOR_LISTENER_SIG = new Class<?>[] { AjaxBehaviorEvent.class };
      
      /**
       * Constant used to check if in the current build view it has been rendered the standard jsf javascript
       * library. It is necessary to remove this key from facesContext attribute map after build, to keep
       * working this code for next views to be built.
       */
      public final static String STANDARD_JSF_AJAX_LIBRARY_LOADED
              = "org.apache.myfaces.STANDARD_JSF_AJAX_LIBRARY_LOADED";
  
     /**
      * 
      */
     @JSFFaceletAttribute(name = "disabled", className = "javax.el.ValueExpression",
                          deferredValueType = "java.lang.Boolean")
     private final TagAttribute _disabled;
 
     /**
      * 
      */
     @JSFFaceletAttribute(name = "event", className = "javax.el.ValueExpression",
                          deferredValueType = "java.lang.String")
     private final TagAttribute _event;
 
     /**
      * 
      */
     @JSFFaceletAttribute(name = "execute", className = "javax.el.ValueExpression",
                          deferredValueType = "java.lang.Object")
     private final TagAttribute _execute;
 
     /**
      * 
      */
     @JSFFaceletAttribute(name = "immediate", className = "javax.el.ValueExpression",
                          deferredValueType = "java.lang.Boolean")
     private final TagAttribute _immediate;
 
     /**
      * 
      */
     @JSFFaceletAttribute(name = "listener", className = "javax.el.MethodExpression",
             deferredMethodSignature = "public void m(javax.faces.event.AjaxBehaviorEvent evt) "
                                       + "throws javax.faces.event.AbortProcessingException")
     private final TagAttribute _listener;
 
     /**
      * 
      */
     @JSFFaceletAttribute(name = "onevent", className = "javax.el.ValueExpression",
                          deferredValueType = "java.lang.String")
     private final TagAttribute _onevent;
 
     /**
      * 
      */
     @JSFFaceletAttribute(name = "onerror", className = "javax.el.ValueExpression",
                          deferredValueType = "java.lang.String")
     private final TagAttribute _onerror;
 
     /**
      * 
      */
     @JSFFaceletAttribute(name = "render", className = "javax.el.ValueExpression",
                          deferredValueType = "java.lang.Object")
     private final TagAttribute _render;
     
     private final boolean _wrapMode;
 
     public AjaxHandler(TagConfig config)
     {
         super(config);
         _disabled = getAttribute("disabled");
         _event = getAttribute("event");
         _execute = getAttribute("execute");
         _immediate = getAttribute("immediate");
         _listener = getAttribute("listener");
         _onerror = getAttribute("onerror");
         _onevent = getAttribute("onevent");
         _render = getAttribute("render");
         
         // According to the spec, this tag works in two different ways:
         // 1. Apply an ajax behavior for a selected component in this way
         //    <x:component><f:ajax ..../></x:component>
         // 2. Apply an ajax behavior for a group of components inside it
         //   <f:ajax ....><x:componentA .../><x:componentB .../></f:ajax>
         //
         // The first problem is how to discriminate if f:ajax tag is on a
         // "leaf" or if contain other components.
         //
         // One option is use the same strategy to cache instance for 
         // <composite:interface> handler: traverse the tree for instances of 
         // ComponentHandler. If it is found, wrapMode is used otherwise
         // suppose f:ajax is the one wrapped by a component.
         Collection<FaceletHandler> compHandlerList = 
             TagHandlerUtils.findNextByType(nextHandler, ComponentHandler.class, 
                     InsertChildrenHandler.class, InsertHandler.class, DecorateHandler.class, IncludeHandler.class);
         
         _wrapMode = !compHandlerList.isEmpty();
     }
 
     public void apply(FaceletContext ctx, UIComponent parent)
             throws IOException
     {
         //Apply only if we are creating a new component
         if (!ComponentHandler.isNew(parent))
         {
             if (_wrapMode)
             {
                 AbstractFaceletContext actx = (AbstractFaceletContext) ctx;
                 // In this case it will be only applied to components inserted by 
                 // c:if or related tags, in other cases, ComponentTagHandlerDelegate should
                 // not reapply ajax tag.
                 actx.pushAjaxHandlerToStack(this);
                 nextHandler.apply(ctx, parent);
                 actx.popAjaxHandlerToStack();
             }
             return;
         }
         if (_wrapMode)
         {
             AbstractFaceletContext actx = (AbstractFaceletContext) ctx;
             // Push and pop this ajax handler to the stack, to delegate the
             // call to applyAttachedObject to ComponentTagHandlerDelegate
             // TODO: The spec is not clear about how to deal with 
             // composite component instances. The default one proposed here is
             // use a different stack on DefaultFaceletContext.applyCompositeComponent,
             // so components inside composite:implementation tag will not be
             // affected by f:ajax outsider handlers.
             actx.pushAjaxHandlerToStack(this);
             nextHandler.apply(ctx, parent);
             actx.popAjaxHandlerToStack();
         }
         else
         {
             if (parent instanceof ClientBehaviorHolder)
             {
                 //Apply this handler directly over the parent
                 applyAttachedObject(ctx.getFacesContext(), parent);
             }
             else if (UIComponent.isCompositeComponent(parent))
             {
                 FaceletCompositionContext mctx = FaceletCompositionContext.getCurrentInstance(ctx);
                 // It is supposed that for composite components, this tag should
                 // add itself as a target, but note that on whole api does not exists
                 // some tag that expose client behaviors as targets for composite
                 // components. In RI, there exists a tag called composite:clientBehavior,
                 // but does not appear on spec or javadoc, maybe because this could be
                 // understand as an implementation detail, after all there exists a key
                 // called AttachedObjectTarget.ATTACHED_OBJECT_TARGETS_KEY that could be
                 // used to create a tag outside jsf implementation to attach targets.
                 mctx.addAttachedObjectHandler(
                         parent, this);
             }
             else
             {
                 throw new TagException(this.tag,
                         "Parent is not composite component or of type ClientBehaviorHolder, type is: "
                                 + parent);
             }
         }
         
         registerJsfAjaxDefaultResource(ctx, parent);
     }
     
     public static void registerJsfAjaxDefaultResource(FaceletContext ctx, UIComponent parent)
     {
         // Register the standard ajax library on the current page in this way:
         //
         // <h:outputScript name="jsf.js" library="javax.faces" target="head"/>
         //
         // If no h:head component is in the page, we must anyway render the script inline,
         // so the only way to make sure we are doing this is add a outputScript component.
         // Note that call directly UIViewRoot.addComponentResource or use a listener 
         // does not work in this case, because check this condition will requires 
         // traverse the whole tree looking for h:head component.
         FacesContext facesContext = ctx.getFacesContext();
         if (!facesContext.getAttributes().containsKey(STANDARD_JSF_AJAX_LIBRARY_LOADED))
         {
             UIComponent outputScript = facesContext.getApplication().
                 createComponent(facesContext, "javax.faces.Output", "javax.faces.resource.Script");
             outputScript.getAttributes().put(JSFAttr.NAME_ATTR, ResourceUtils.JSF_JS_RESOURCE_NAME);
             outputScript.getAttributes().put(JSFAttr.LIBRARY_ATTR, ResourceUtils.JAVAX_FACES_LIBRARY_NAME);
             outputScript.getAttributes().put(JSFAttr.TARGET_ATTR, "head");
 
             //AbstractFaceletContext actx = (AbstractFaceletContext) ctx;
 
             // Since this component will be relocated, we need a generated clientId from the
             // viewRoot, so when this one is relocated, its parent will be this UIViewRoot instance
             // and prevent a duplicate id exception.
             UniqueIdVendor uniqueIdVendor = ComponentSupport.getViewRoot(ctx, parent);
             // UIViewRoot implements UniqueIdVendor, so there is no need to cast to UIViewRoot
             // and call createUniqueId()
             String uid = uniqueIdVendor.createUniqueId(ctx.getFacesContext(),null);
             outputScript.setId(uid);
             
             parent.getChildren().add(outputScript);
             
             if (FaceletCompositionContext.getCurrentInstance(ctx).isMarkInitialState())
             {
                 //Call it only if we are using partial state saving
                 outputScript.markInitialState();
             }            
             facesContext.getAttributes().put(STANDARD_JSF_AJAX_LIBRARY_LOADED, Boolean.TRUE);
         }
     }
 
     /**
      * ViewDeclarationLanguage.retargetAttachedObjects uses it to check
      * if the the target to be processed is applicable for this handler
      */
     public String getEventName()
     {
         if (_event == null)
         {
             return null;
         }
         else
         {
             return _event.getValue();
         }
     }
 
     /**
      * This method should create an AjaxBehavior object and attach it to the
      * parent component.
      * 
      * Also, it should check if the parent can apply the selected AjaxBehavior
      * to the selected component through ClientBehaviorHolder.getEventNames() or
      * ClientBehaviorHolder.getDefaultEventName()
      */
     public void applyAttachedObject(FacesContext context, UIComponent parent)
     {
         // Retrieve the current FaceletContext from FacesContext object
         FaceletContext faceletContext = (FaceletContext) context
                 .getAttributes().get(FaceletContext.FACELET_CONTEXT_KEY);
 
         // cast to a ClientBehaviorHolder
         ClientBehaviorHolder cvh = (ClientBehaviorHolder) parent;
         
         String eventName = getEventName();
         if (eventName == null)
         {
             eventName = cvh.getDefaultEventName();
             if (eventName == null)
             {
                 if (_wrapMode)
                 {
                     // No eventName defined, we can't apply this tag to this component, because
                     // there is no event defined to attach it, but since we are in wrap mode
                     // we have here the case that the component could not be the target
                     // for this attached object.
                     return;
                 }
                 else
                 {
                     throw new TagAttributeException(_event,
                             "eventName could not be defined for f:ajax tag with no wrap mode.");
                 }
             }
         }
         else if (!cvh.getEventNames().contains(eventName))
         {
             if (_wrapMode)
             {
                 // The current component does not implement the event selected,
                 // this ajax behavior cannot be applied, but we can't throw any exception
                 // since we are in wrap mode and we have here the case that the 
                 // component could not be the target for this attached object.
                 return;
             }
             else
             {
                 throw new TagAttributeException(_event,
                         "event it is not a valid eventName defined for this component");
             }
         }
         
         Map<String, List<ClientBehavior>> clientBehaviors = cvh.getClientBehaviors();
 
         List<ClientBehavior> clientBehaviorList = clientBehaviors.get(eventName);
         if (clientBehaviorList != null && !clientBehaviorList.isEmpty())
         {
             for (ClientBehavior cb : clientBehaviorList)
             {
                 if (cb instanceof AjaxBehavior)
                 {
                     // The most inner one has been applied, so according to 
                     // jsf 2.0 spec section 10.4.1.1 it is not necessary to apply
                     // this one, because the inner one has precendece over
                     // the outer one.
                     return;
                 }
             }
         }
 
         AjaxBehavior ajaxBehavior = createBehavior(context);
 
         if (_disabled != null)
         {
             if (_disabled.isLiteral())
             {
                 ajaxBehavior.setDisabled(_disabled.getBoolean(faceletContext));
             }
             else
             {
                 ajaxBehavior.setValueExpression("disabled", _disabled
                         .getValueExpression(faceletContext, Boolean.class));
             }
         }
         if (_execute != null)
         {
             ajaxBehavior.setValueExpression("execute", _execute
                     .getValueExpression(faceletContext, Object.class));
         }
         if (_immediate != null)
         {
             if (_immediate.isLiteral())
             {
                 ajaxBehavior
                         .setImmediate(_immediate.getBoolean(faceletContext));
             }
             else
             {
                 ajaxBehavior.setValueExpression("immediate", _immediate
                         .getValueExpression(faceletContext, Boolean.class));
             }
         }
         if (_listener != null)
         {
             MethodExpression expr = _listener.getMethodExpression(
                     faceletContext, Void.TYPE, AJAX_BEHAVIOR_LISTENER_SIG);
             AjaxBehaviorListener abl = new AjaxBehaviorListenerImpl(expr);
             ajaxBehavior.addAjaxBehaviorListener(abl);
         }
         if (_onerror != null)
         {
             if (_onerror.isLiteral())
             {
                 ajaxBehavior.setOnerror(_onerror.getValue(faceletContext));
             }
             else
             {
                 ajaxBehavior.setValueExpression("onerror", _onerror
                         .getValueExpression(faceletContext, String.class));
             }
         }
         if (_onevent != null)
         {
             if (_onevent.isLiteral())
             {
                 ajaxBehavior.setOnevent(_onevent.getValue(faceletContext));
             }
             else
             {
                 ajaxBehavior.setValueExpression("onevent", _onevent
                         .getValueExpression(faceletContext, String.class));
             }
         }
         if (_render != null)
         {
             ajaxBehavior.setValueExpression("render", _render
                     .getValueExpression(faceletContext, Object.class));
         }
         
         cvh.addClientBehavior(eventName, ajaxBehavior);
     }
 
     protected AjaxBehavior createBehavior(FacesContext context)
     {
         return (AjaxBehavior) context.getApplication().createBehavior(AjaxBehavior.BEHAVIOR_ID);
     }
 
     /**
      * The documentation says this attribute should not be used since it is not
      * taken into account. Instead, getEventName is used on 
      * ViewDeclarationLanguage.retargetAttachedObjects.
      */
     public String getFor()
     {
         return null;
     }
 
     /**
      * Wraps a method expression in a AjaxBehaviorListener
      */
     public final static class AjaxBehaviorListenerImpl implements
             AjaxBehaviorListener, PartialStateHolder
     {
         private MethodExpression _expr;
         private boolean _transient;
         private boolean _initialStateMarked;
         
         public AjaxBehaviorListenerImpl ()
         {
         }
         
         public AjaxBehaviorListenerImpl(MethodExpression expr)
         {
             _expr = expr;
         }
 
         public void processAjaxBehavior(AjaxBehaviorEvent event)
                 throws AbortProcessingException
         {
             _expr.invoke(FacesContext.getCurrentInstance().getELContext(),
                     new Object[] { event });
         }
 
         public boolean isTransient()
         {
             return _transient;
         }
 
         public void restoreState(FacesContext context, Object state)
         {
             if (state == null)
             {
                 return;
             }
             _expr = (MethodExpression) state;
         }
 
         public Object saveState(FacesContext context)
         {
             if (initialStateMarked())
             {
                 return null;
             }
             return _expr;
         }
 
         public void setTransient(boolean newTransientValue)
         {
             _transient = newTransientValue;
         }
         
         public void clearInitialState()
         {
             _initialStateMarked = false;
         }
 
         public boolean initialStateMarked()
         {
             return _initialStateMarked;
         }
 
         public void markInitialState()
         {
             _initialStateMarked = true;
         }
     }
 }