/**
    * Copyright 2005-2006 the original author or authors.
    *
    * Licensed under the Gnu General Pubic 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.opensource.org/licenses/gpl-license.php
    *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   * See the Gnu General Public License for more details.
   */
  package org.figure8.join.control;
  
  import javax.servlet.ServletException;
  import javax.servlet.UnavailableException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.io.FileInputStream;
  import java.io.BufferedInputStream;
  import java.util.zip.GZIPOutputStream;
  /**
   * Servlet that allows to download a file which full UNC path is put
   * into to the query parameters ("path" denotes the directory and "file"
   * short name of file itself).
   * @author  <a href="mailto:laurent.broudoux@free.fr">Laurent Broudoux</a>
   * @version $Revision: 1.2 $
   */
  public class DownloadServlet extends HttpServlet{
     
     // Attributes ---------------------------------------------------------------
     
     /** URL to redirect to in case the specified file does not exists. */
     protected String notExistsURL;
     /** URL to redirect to in case the specified file is not readable. */
     protected String notReadableURL;
     
     
     // Override of HttpServlet --------------------------------------------------
     
     /**
      * Override of default init() method. Call super.init() and then retrieve
      * and store servlet parameters.
      * @throws ServletException if one init parameter is missing
      */
     public void init() throws ServletException{
        // Make sure to always call the super's init() first.
        super.init();
        
        // Retrieve servlet init parameters and check them.
        notExistsURL = getInitParameter("file.doesnot.exists.url");
        notReadableURL = getInitParameter("file.is.not.readable.url");
        
        if (notExistsURL == null || notExistsURL.length() == 0)
           throw new UnavailableException("The file.doesnot.exists.url parameter is mandatory");
        if (notReadableURL == null || notReadableURL.length() == 0)
           throw new UnavailableException("The file.is.not.readable.url parameter is mandatory");
     }
     
     /**
      * Override of default <code>doGet()</code> method: just call the protected
      * <code>downloadFile()</code> method, passing around request and response.
      * @param request The http request (containing query string specifying file)
      * @param response Thee http response (for writing ouput)
      * @throws IOException if requested file cannot be opened or written to response
      * @throws ServletException in any other exception case
      */
     public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        // Just call downloadFile() ...
        downloadFile(request, response);
     }
     
     
     // Protected ----------------------------------------------------------------
     
     /**
      * Retrieve the file to download path from query string. Make some
      * check (non null, existence, readability) before dumping the file
      * into ouputstream. If gzip encoding is supported, wrap the dump into
      * a GZIPOutputStream to save bandwidth ...
      * @param request The http request (containing parameters specifying file)
      * @param response Thee http response (for writing ouput)
      * @throws IOException if outputstream cannot be opened or written
      */
     protected void downloadFile(HttpServletRequest request, HttpServletResponse response) throws IOException{
        // Retrieve file path.
        String pathStr = request.getParameter("path");
        String fileStr = request.getParameter("file");
        
        if (pathStr != null && pathStr.length() > 0
                && fileStr != null && fileStr.length() > 0){
           // Build the file object corresponding.
          File file = new File(pathStr, fileStr);
          
          if (file.exists()){
             if (file.canRead()){
                // Get file name and encoding.
                String name = file.getName();
                String encoding = request.getHeader("Accept-Encoding");
                
                if (encoding != null && encoding.indexOf("gzip") != -1){
                   response.setHeader("Content-Encoding", "gzip");
                   response.setHeader("Content-Disposition", "attachment;filename=\"" + name + "\"");
                   GZIPOutputStream os = new GZIPOutputStream(response.getOutputStream());
                   dumpFile(file, os);
                }
                else{
                   response.setContentType("application/octet-stream");
                   response.setHeader("Content-Disposition", "attachment;filename=\"" + name + "\"");
                   dumpFile(file, response.getOutputStream());
                }
             }
             else response.sendRedirect(request.getContextPath() + notReadableURL);
          }
          else response.sendRedirect(request.getContextPath() + notExistsURL);
       }
    }
    
    /**
     * Dump a file content into the given ouput stream.
     * Best efforts are made to cleanly flush & close input and ouput streams.
     * @param file The file to dump
     * @param os The ouput stream to dump in
     */
    protected void dumpFile(File file, OutputStream os){
       // Prepare materials.
       int i;
       byte[] bytes = new byte[4096];
       BufferedInputStream is = null;
       
       try{
          is = new BufferedInputStream(new FileInputStream(file));
          while((i = is.read(bytes, 0, 4096)) != -1)
             os.write(bytes, 0, i);
       }
       catch (Exception e){
          // Nothing to do here...
       }
       finally{
          // Try closing input & output streams.
          try {is.close();}
          catch (Exception ee) {/* Do nothing here... */}
          try {os.flush(); os.close();}
          catch (Exception ee) {/* Do nothing here... */}
       }
    }
 }