// Copyright 2007-2013 The Apache Software Foundation
   //
   // Licensed 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.tapestry5.internal.services;
  
  import java.io.IOException;
  
  import org.apache.tapestry5.TrackableComponentEventCallback;
  import org.apache.tapestry5.internal.InternalConstants;
  import org.apache.tapestry5.internal.structure.ComponentPageElement;
  import org.apache.tapestry5.internal.structure.Page;
  import org.apache.tapestry5.internal.util.Holder;
  import org.apache.tapestry5.ioc.internal.util.TapestryException;
  import org.apache.tapestry5.json.JSONObject;
  import org.apache.tapestry5.services.Ajax;
  import org.apache.tapestry5.services.ComponentEventRequestHandler;
  import org.apache.tapestry5.services.ComponentEventRequestParameters;
  import org.apache.tapestry5.services.ComponentEventResultProcessor;
  import org.apache.tapestry5.services.Environment;
  import org.apache.tapestry5.services.Request;
  
  /**
   * Similar to {@link ComponentEventRequestHandlerImpl}, but built around the Ajax request cycle, where the action
   * request sends back an immediate JSON response containing the new content.
   */
  @SuppressWarnings({"unchecked", "rawtypes"})
  public class AjaxComponentEventRequestHandler implements ComponentEventRequestHandler
  {
      private final RequestPageCache cache;
  
      private final Request request;
  
      private final PageRenderQueue queue;
  
      private final ComponentEventResultProcessor resultProcessor;
  
      private final Environment environment;
  
      private final AjaxPartialResponseRenderer partialRenderer;
  
      private final PageActivator pageActivator;
  
      public AjaxComponentEventRequestHandler(RequestPageCache cache, Request request, PageRenderQueue queue, @Ajax
      ComponentEventResultProcessor resultProcessor, PageActivator pageActivator,
                                              Environment environment,
                                              AjaxPartialResponseRenderer partialRenderer)
      {
          this.cache = cache;
          this.queue = queue;
          this.resultProcessor = resultProcessor;
          this.pageActivator = pageActivator;
          this.request = request;
          this.environment = environment;
          this.partialRenderer = partialRenderer;
      }
  
      public void handle(ComponentEventRequestParameters parameters) throws IOException
      {
          Page activePage = cache.get(parameters.getActivePageName());
  
          final Holder<Boolean> resultProcessorInvoked = Holder.create();
          resultProcessorInvoked.put(false);
  
          ComponentEventResultProcessor interceptor = new ComponentEventResultProcessor()
          {
              public void processResultValue(Object value) throws IOException
              {
                  resultProcessorInvoked.put(true);
  
                  resultProcessor.processResultValue(value);
              }
          };
  
          // If we end up doing a partial render, the page render queue service needs to know the
          // page that will be rendered (for logging purposes, if nothing else).
  
          queue.setRenderingPage(activePage);
  
          request.setAttribute(InternalConstants.PAGE_NAME_ATTRIBUTE_NAME, parameters.getActivePageName());
  
          if (pageActivator.activatePage(activePage.getRootElement().getComponentResources(), parameters
                  .getPageActivationContext(), interceptor))
              return;
  
          Page containerPage = cache.get(parameters.getContainingPageName());
  
          ComponentPageElement element = containerPage.getComponentElementByNestedId(parameters.getNestedComponentId());
  
         // In many cases, the triggered element is a Form that needs to be able to
         // pass its event handler return values to the correct result processor.
         // This is certainly the case for forms.
 
         TrackableComponentEventCallback callback = new ComponentResultProcessorWrapper(interceptor);
 
         environment.push(ComponentEventResultProcessor.class, interceptor);
         environment.push(TrackableComponentEventCallback.class, callback);
 
         boolean handled = element
                 .triggerContextEvent(parameters.getEventType(), parameters.getEventContext(), callback);
 
         if (!handled)
             throw new TapestryException(String.format("Request event '%s' (on component %s) was not handled; you must provide a matching event handler method in the component or in one of its containers.", parameters.getEventType(), element.getCompleteId()), element,
                     null);
 
         environment.pop(TrackableComponentEventCallback.class);
         environment.pop(ComponentEventResultProcessor.class);
 
 
         // If the result processor was passed a value, then it will already have rendered. Otherwise it was not passed a value,
         // but it's still possible that we still want to do a partial page render ... if filters were added to the render queue.
         // In that event, run the partial page render now and return.
 
         boolean wasInvoked = resultProcessorInvoked.get();
 
         if ((!wasInvoked) && queue.isPartialRenderInitialized())
         {
             partialRenderer.renderPartialPageMarkup();
             return;
         }
 
         // If the result processor was passed a value, then it will already have rendered, and there is nothing more to do.
 
         if (wasInvoked) { return; }
 
         // Send an empty JSON reply if no value was returned from the component event handler method.
         // This is the typical behavior when an Ajax component event handler returns null. It still
         // will go through a pipeline that will add information related to partial page rendering.
 
         resultProcessor.processResultValue(new JSONObject());
     }
 }