//
   //  ========================================================================
   //  Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
   //  ------------------------------------------------------------------------
   //  All rights reserved. This program and the accompanying materials
   //  are made available under the terms of the Eclipse Public License v1.0
   //  and Apache License v2.0 which accompanies this distribution.
   //
   //      The Eclipse Public License is available at
  //      http://www.eclipse.org/legal/epl-v10.html
  //
  //      The Apache License v2.0 is available at
  //      http://www.opensource.org/licenses/apache2.0.php
  //
  //  You may elect to redistribute this code under either of these licenses.
  //  ========================================================================
  //
  
  package org.eclipse.jetty.servlets;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  
  import javax.servlet.RequestDispatcher;
  import javax.servlet.ServletContext;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.eclipse.jetty.util.URIUtil;
  
  /**
   * <p>This servlet may be used to concatenate multiple resources into
   * a single response.</p>
   * <p>It is intended to be used to load multiple
   * javascript or css files, but may be used for any content of the
   * same mime type that can be meaningfully concatenated.</p>
   * <p>The servlet uses {@link RequestDispatcher#include(javax.servlet.ServletRequest, javax.servlet.ServletResponse)}
   * to combine the requested content, so dynamically generated content
   * may be combined (Eg engine.js for DWR).</p>
   * <p>The servlet uses parameter names of the query string as resource names
   * relative to the context root.  So these script tags:</p>
   * <pre>
   * &lt;script type="text/javascript" src="../js/behaviour.js"&gt;&lt;/script&gt;
   * &lt;script type="text/javascript" src="../js/ajax.js"&gt;&lt;/script&gt;
   * &lt;script type="text/javascript" src="../chat/chat.js"&gt;&lt;/script&gt;
   * </pre>
   * <p>can be replaced with the single tag (with the {@code ConcatServlet}
   * mapped to {@code /concat}):</p>
   * <pre>
   * &lt;script type="text/javascript" src="../concat?/js/behaviour.js&amp;/js/ajax.js&amp;/chat/chat.js"&gt;&lt;/script&gt;
   * </pre>
   * <p>The {@link ServletContext#getMimeType(String)} method is used to determine the
   * mime type of each resource. If the types of all resources do not match, then a 415
   * UNSUPPORTED_MEDIA_TYPE error is returned.</p>
   * <p>If the init parameter {@code development} is set to {@code true} then the servlet
   * will run in development mode and the content will be concatenated on every request.</p>
   * <p>Otherwise the init time of the servlet is used as the lastModifiedTime of the combined content
   * and If-Modified-Since requests are handled with 304 NOT Modified responses if
   * appropriate. This means that when not in development mode, the servlet must be
   * restarted before changed content will be served.</p>
   */
  public class ConcatServlet extends HttpServlet
  {
      private boolean _development;
      private long _lastModified;
  
      @Override
      public void init() throws ServletException
      {
          _lastModified = System.currentTimeMillis();
          _development = Boolean.parseBoolean(getInitParameter("development"));
      }
  
      /*
       * @return The start time of the servlet unless in development mode, in which case -1 is returned.
       */
      @Override
      protected long getLastModified(HttpServletRequest req)
      {
          return _development ? -1 : _lastModified;
      }
  
      @Override
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
      {
          String query = request.getQueryString();
          if (query == null)
          {
              response.sendError(HttpServletResponse.SC_NO_CONTENT);
              return;
          }
  
          List<RequestDispatcher> dispatchers = new ArrayList<>();
          String[] parts = query.split("\\&");
          String type = null;
          for (String part : parts)
         {
             String path = URIUtil.canonicalPath(URIUtil.decodePath(part));
             if (path == null)
             {
                 response.sendError(HttpServletResponse.SC_NOT_FOUND);
                 return;
             }
 
             // Verify that the path is not protected.
             if (startsWith(path, "/WEB-INF/") || startsWith(path, "/META-INF/"))
             {
                 response.sendError(HttpServletResponse.SC_NOT_FOUND);
                 return;
             }
 
             String t = getServletContext().getMimeType(path);
             if (t != null)
             {
                 if (type == null)
                 {
                     type = t;
                 }
                 else if (!type.equals(t))
                 {
                     response.sendError(HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE);
                     return;
                 }
             }
 
             RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(path);
             if (dispatcher != null)
                 dispatchers.add(dispatcher);
         }
 
         if (type != null)
             response.setContentType(type);
 
         for (RequestDispatcher dispatcher : dispatchers)
             dispatcher.include(request, response);
     }
 
     private boolean startsWith(String path, String prefix)
     {
         // Case insensitive match.
         return prefix.regionMatches(true, 0, path, 0, prefix.length());
     }
 }