/*
    * $Id: PublisherRenderer.java 1306435 2012-03-28 15:39:11Z nlebas $
    *
    * 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.tiles.request.render;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.tiles.request.Request;
  
  /**
   * Provides a Publisher-Subscriber implementation around the provided renderer to delegate to.
   *
   * @version $Rev: 1035784 $ $Date: 2010-11-16 20:24:12 +0000 (Tue, 16 Nov 2010) $
   */
  public class PublisherRenderer implements Renderer {
  
      public interface RendererListener{
          /** Called before the delegate's render method is called. */
          void start(String template, Request request) throws IOException;
          /** Called after the delegate's render method is called. */
          void end(String template, Request request) throws IOException;
          /** If the delegate render method throws an IOException it is passed through this. */
          void handleIOException(IOException ex, Request request) throws IOException;
      }
  
      private final Renderer renderer;
      private final List<RendererListener> listeners = new ArrayList<RendererListener>();
      private final List<RendererListener> listenersReversed = new ArrayList<RendererListener>();
  
      public PublisherRenderer(Renderer renderer){
          this.renderer = renderer;
      }
  
      @Override
      public void render(String path, Request request) throws IOException {
          if (path == null) {
              throw new CannotRenderException("Cannot dispatch a null path");
          }
          try{
              for(RendererListener listener : listeners){
                  listener.start(path, request);
              }
              renderer.render(path, request);
          }catch(IOException ex){
              handleIOException(ex, request);
          }finally{
              for(RendererListener wrapper : listenersReversed){
                  wrapper.end(path, request);
              }
          }
      }
  
      @Override
      public boolean isRenderable(String path, Request request) {
          return renderer.isRenderable(path, request);
      }
  
      public void addListener(RendererListener listener){
          listeners.add(listener);
          listenersReversed.clear();
          listenersReversed.addAll(listeners);
          Collections.reverse(listenersReversed);
      }
  
      private void handleIOException(IOException exception, Request request) throws IOException{
          IOException ex = exception;
          boolean throwIt = listeners.isEmpty();
          for(RendererListener listener : listenersReversed){
              try{
                  listener.handleIOException(ex, request);
                  throwIt = false;
              }catch(IOException newEx){
                  ex = newEx;
                  throwIt = true;
              }
          }
          if(throwIt){
              throw ex;
          }
     }
 }