/*
    * $Id$
    *
    * 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.web.util;
  
  import java.io.IOException;
  
  import javax.servlet.ServletException;
  import javax.servlet.ServletRequest;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.apache.tiles.AttributeContext;
  import org.apache.tiles.TilesContainer;
  import org.apache.tiles.reflect.ClassUtil;
  import org.apache.tiles.servlet.context.ServletUtil;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Tiles dispatching servlet.  Used to invoke
   * a definition directly.
   */
  public class TilesDispatchServlet extends HttpServlet {
  
      /**
       * Init parameter to define the key of the container to use.
       *
       * @since 2.1.2
       */
      public static final String CONTAINER_KEY_INIT_PARAMETER =
          "org.apache.tiles.web.util.TilesDispatchServlet.CONTAINER_KEY";
  
      /**
       * The logging object.
       */
      private final Logger log = LoggerFactory
              .getLogger(TilesDispatchServlet.class);
  
      /**
       * The key under which the container is stored.
       */
      private String containerKey;
  
      /**
       * The object that will mutate the attribute context so that it uses
       * different attributes.
       */
      private AttributeContextMutator mutator;
  
  
      /** {@inheritDoc} */
      public void init() throws ServletException {
          super.init();
  
          containerKey = getServletConfig().getInitParameter(
                  CONTAINER_KEY_INIT_PARAMETER);
  
          String temp = getInitParameter("mutator");
          if (temp != null) {
              try {
                  mutator = (AttributeContextMutator) ClassUtil.instantiate(temp);
              } catch (Exception e) {
                  throw new ServletException("Unable to instantiate specified context mutator.", e);
              }
          } else {
              mutator = new DefaultMutator();
          }
      }
  
      /** {@inheritDoc} */
      protected void doGet(HttpServletRequest req, HttpServletResponse res)
          throws ServletException, IOException {
  
          TilesContainer container = ServletUtil.getContainer(
                  getServletContext(), containerKey);
          mutator.mutate(container.getAttributeContext(req, res), req);
          String definition = getDefinitionName(req);
          if (log.isDebugEnabled()) {
              log.info("Dispatching to tile '" + definition + "'");
          }
         container.render(definition, req, res);
     }
 
     /**
      * Returns the called definition name for the given request.
      *
      * @param request The request to parse.
      * @return The definition name to render.
      */
     protected String getDefinitionName(HttpServletRequest request) {
         String path = (String) request.getAttribute("javax.servlet.include.servlet_path");
         if (path == null) {
             path = request.getServletPath();
         }
 
         int start = path.startsWith("/") ? 1 : 0;
         int end = path.endsWith(".tiles") ? path.indexOf(".tiles") : path.length();
 
         return path.substring(start, end);
     }
 
     /** {@inheritDoc} */
     protected void doPost(HttpServletRequest req, HttpServletResponse res)
         throws ServletException, IOException {
         log.info("Tiles dispatch request received. Redirecting POST to GET.");
         doGet(req, res);
     }
 
     /**
      * Default no-op mutator.
      */
     class DefaultMutator implements AttributeContextMutator {
 
         /** {@inheritDoc} */
         public void mutate(AttributeContext context, ServletRequest request) {
             // noop;
         }
     }
 }