/*
    * $Id: ModularTilesInitializer.java 1297705 2012-03-06 20:44:30Z 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.extras.module;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.List;
  import java.util.jar.Attributes;
  import java.util.jar.Manifest;
  
  import javax.servlet.ServletContext;
  
  import org.apache.tiles.definition.DefinitionsFactoryException;
  import org.apache.tiles.request.ApplicationContext;
  import org.apache.tiles.request.ApplicationResource;
  import org.apache.tiles.request.reflect.ClassUtil;
  import org.apache.tiles.request.servlet.wildcard.WildcardServletApplicationContext;
  import org.apache.tiles.startup.TilesInitializer;
  
  /**
   * Loads Tiles modules, initializes them and destroy them at the end.<br>
   * It loads all META-INF/MANIFEST.MF files, checks for the "Tiles-Initializer"
   * property that must contain a valid class name of a {@link TilesInitializer}.
   * After that, initializes all found initializers, one by one. When the
   * {@link #destroy()} method is called, all the initializers are then destroyed.
   *
   * @version $Rev: 1297705 $ $Date: 2012-03-07 07:44:30 +1100 (Wed, 07 Mar 2012) $
   * @since 2.2.1
   */
  public class ModularTilesInitializer implements TilesInitializer {
  
      /**
       * The initializers to use.
       */
      private List<TilesInitializer> initializers;
  
      /** {@inheritDoc} */
      public void initialize(ApplicationContext preliminaryContext) {
          ApplicationContext applicationContext = new WildcardServletApplicationContext(
                  (ServletContext) preliminaryContext.getContext());
          loadInitializers(applicationContext);
  
          for (TilesInitializer initializer : initializers) {
              initializer.initialize(preliminaryContext);
          }
      }
  
      /** {@inheritDoc} */
      public void destroy() {
          for (TilesInitializer initializer : initializers) {
              initializer.destroy();
          }
      }
  
      /**
       * Load all the initializers from manifest files.
       *
       * @param applicationContext The application context.
       */
      private void loadInitializers(ApplicationContext applicationContext) {
          initializers = new ArrayList<TilesInitializer>();
          try {
              Collection<ApplicationResource> resources = applicationContext
                      .getResources("classpath*:META-INF/MANIFEST.MF");
              ApplicationResource mainResource = applicationContext.getResource("/META-INF/MANIFEST.MF");
              if (mainResource != null) {
                  resources.add(mainResource);
              }
              for (ApplicationResource resource : resources) {
                  InputStream stream = resource.getInputStream();
                  try {
                      Manifest manifest = new Manifest(stream);
                      Attributes attributes = manifest.getMainAttributes();
                      if (attributes != null) {
                          String initializerName = attributes.getValue("Tiles-Initializer");
                          if (initializerName != null) {
                              TilesInitializer initializer = (TilesInitializer) ClassUtil
                                      .instantiate(initializerName);
                             initializers.add(initializer);
                         }
                     }
                 } finally {
                     stream.close();
                 }
             }
         } catch (IOException e) {
             throw new DefinitionsFactoryException("Error getting manifest files", e);
         }
     }
 }