/*
    * 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.context.servlet;
  
  import java.io.InputStream;
  import java.net.MalformedURLException;
  import java.net.URL;
  import java.util.Map;
  import java.util.Set;
  
  import javax.faces.context.ExternalContext;
  import javax.servlet.ServletContext;
  
  import org.apache.myfaces.context.ReleaseableExternalContext;
  
  /**
   * Provides a base implementation of the ExternalContext for Servlet
   * environments. This impl provides all methods which only rely on the
   * ServletContext and thus are also provided at startup and shutdown.
   * 
   * @author Jakob Korherr (latest modification by $Author: jakobk $)
   * @version $Revision: 956589 $ $Date: 2010-06-21 08:43:21 -0500 (Mon, 21 Jun 2010) $
   */
  public abstract class ServletExternalContextImplBase extends ExternalContext
          implements ReleaseableExternalContext
  {
      
      private static final String INIT_PARAMETER_MAP_ATTRIBUTE = InitParameterMap.class.getName();
      
      private ServletContext _servletContext;
      private Map<String, Object> _applicationMap;
      private Map<String, String> _initParameterMap;
      
      public ServletExternalContextImplBase(ServletContext servletContext)
      {
          _servletContext = servletContext;
          _applicationMap = null;
          _initParameterMap = null;
      }
      
      public void release()
      {
          _servletContext = null;
          _applicationMap = null;
          _initParameterMap = null;
      }
      
      // ~ Methods which only rely on the ServletContext-------------------------
      
      @Override
      public Map<String, Object> getApplicationMap()
      {
          if (_applicationMap == null)
          {
              _applicationMap = new ApplicationMap(_servletContext);
          }
          return _applicationMap;
      }
      
      @Override
      public String getMimeType(String file)
      {
          checkNull(file, "file");
          return _servletContext.getMimeType(file);
      }
      
      @Override
      public Object getContext()
      {
          return _servletContext;
      }
      
      @Override
      public String getContextName() 
      {
          return _servletContext.getServletContextName();
      }
      
      @Override
      public String getInitParameter(final String s)
      {
          return _servletContext.getInitParameter(s);
      }
 
     @Override
     @SuppressWarnings("unchecked")
     public Map<String, String> getInitParameterMap()
     {
         if (_initParameterMap == null)
         {
             // We cache it as an attribute in ServletContext itself (is this circular reference a problem?)
             if ((_initParameterMap = (Map<String, String>) _servletContext.getAttribute(INIT_PARAMETER_MAP_ATTRIBUTE)) == null)
             {
                 _initParameterMap = new InitParameterMap(_servletContext);
                 _servletContext.setAttribute(INIT_PARAMETER_MAP_ATTRIBUTE, _initParameterMap);
             }
         }
         return _initParameterMap;
     }
     
     @Override
     public URL getResource(final String path) throws MalformedURLException
     {
         checkNull(path, "path");
         return _servletContext.getResource(path);
     }
 
     @Override
     public InputStream getResourceAsStream(final String path)
     {
         checkNull(path, "path");
         return _servletContext.getResourceAsStream(path);
     }
 
     @Override
     @SuppressWarnings("unchecked")
     public Set<String> getResourcePaths(final String path)
     {
         checkNull(path, "path");
         return _servletContext.getResourcePaths(path);
     }
 
     @Override
     public void log(final String message)
     {
         checkNull(message, "message");
         _servletContext.log(message);
     }
 
     @Override
     public void log(final String message, final Throwable exception)
     {
         checkNull(message, "message");
         checkNull(exception, "exception");
         _servletContext.log(message, exception);
     }
     
     @Override
     public String getRealPath(String path)
     {
         checkNull(path, "path");
         return _servletContext.getRealPath(path);
     }
     
     // ~ Methods which verify some required behavior---------------------------
     
     protected void checkNull(final Object o, final String param)
     {
         if (o == null)
         {
             throw new NullPointerException(param + " can not be null.");
         }
     }
     
 }