/*
    * $Id: ServletUtil.java 1375743 2012-08-21 20:05:58Z 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.servlet;
  
  import java.io.IOException;
  
  import javax.servlet.ServletContext;
  import javax.servlet.ServletException;
  
  import org.apache.tiles.request.ApplicationContext;
  import org.apache.tiles.request.ApplicationAccess;
  import org.apache.tiles.request.RequestWrapper;
  import org.apache.tiles.request.Request;
  
  /**
   * Utilities for Tiles request servlet support.
   *
   * @version $Rev: 1375743 $ $Date: 2012-08-22 06:05:58 +1000 (Wed, 22 Aug 2012) $
   */
  public final class ServletUtil {
  
      /**
       * Constructor.
       */
      private ServletUtil() {
      }
  
      /**
       * Wraps a ServletException to create an IOException with the root cause if present.
       *
       * @param ex The exception to wrap.
       * @param message The message of the exception.
       * @return The wrapped exception.
       */
      public static IOException wrapServletException(ServletException ex,
              String message) {
          IOException retValue;
          Throwable rootCause = ex.getRootCause();
          if (rootCause != null) {
              // Replace the ServletException with an IOException, with the root
              // cause of the first as the cause of the latter.
              retValue = new IOException(message, rootCause);
          } else {
              retValue = new IOException(message, ex);
          }
  
          return retValue;
      }
  
      /**
       * Returns the application context getting it from the servlet context. It must be
       * first saved creating a {@link ServletApplicationContext} and using
       * {@link ApplicationAccess#register(ApplicationContext)}.
       *
       * @param servletContext The servlet context.
       * @return The application context, if found, <code>null</code> otherwise.
       */
      public static ApplicationContext getApplicationContext(ServletContext servletContext) {
          return (ApplicationContext) servletContext
                  .getAttribute(ApplicationAccess.APPLICATION_CONTEXT_ATTRIBUTE);
      }
  
      /**
       * Opens a TilesRequestContext until it finds a ServletTilesRequestContext.
       *
       * @param request The request to open.
       * @return The servlet-based request context.
       * @throws NotAServletEnvironmentException If a servlet-based request
       * context could not be found.
       */
      public static ServletRequest getServletRequest(Request request) {
          Request currentRequest = request;
          while (true) {
              if (currentRequest == null) {
                  throw new NotAServletEnvironmentException("Last Tiles request context is null");
              }
  
              if (currentRequest instanceof ServletRequest) {
                  return (ServletRequest) currentRequest;
              }
             if (!(currentRequest instanceof RequestWrapper)) {
                 throw new NotAServletEnvironmentException("Not a Servlet environment, not supported");
             }
             currentRequest = ((RequestWrapper) currentRequest).getWrappedRequest();
         }
     }
 
     /**
      * Gets a servlet context from a TilesApplicationContext.
      *
      * @param applicationContext The application context to analyze.
      * @return The servlet context.
      * @throws NotAServletEnvironmentException If the application context is not
      * servlet-based.
      */
     public static ServletContext getServletContext(ApplicationContext applicationContext) {
         if (applicationContext instanceof ServletApplicationContext) {
             return (ServletContext) ((ServletApplicationContext) applicationContext).getContext();
         }
 
         throw new NotAServletEnvironmentException("Not a Servlet-based environment");
     }
 }