/**********************************************
    * Copyright (C) 2010 Lukas Laag
    * This file is part of vectomatic2.
    * 
    * vectomatic2 is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    * 
   * vectomatic2 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.
   * 
   * You should have received a copy of the GNU General Public License
   * along with vectomatic2.  If not, see http://www.gnu.org/licenses/
   **********************************************/
  package org.vectomatic.svg.edit.server;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.net.URL;
  
  import javax.servlet.ServletConfig;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServlet;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  /**
   * Servlet to fetch resources from domains outside
   * the vectomatic domain.
   */
  public class FetchServlet extends HttpServlet {
  	private static final long serialVersionUID = 1L;
  	private static final int MAX_SIZE = 1024 * 256;
  	private static final String PARAM_URL = "url";
  	private static final String PARAM_TYPE = "type";
  	private static final String HTTP_PROTOCOL = "http";
  
      /**
       * Default constructor. 
       */
      public FetchServlet() {
      }
      
      @Override
      public void init(ServletConfig config) throws ServletException {
      }
  
  	/**
  	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
  	 */
      @Override
  	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  		URL url = new URL(request.getParameter(PARAM_URL));
  		String contentType = request.getParameter(PARAM_TYPE);
  		System.out.println("Fetching: " + url.toExternalForm() + " contentType: " + contentType);
  		// Reject all non HTTP urls
  		if (!HTTP_PROTOCOL.equals(url.getProtocol())) {
  			response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Unsupported protocol: " + url.getProtocol());
  		} else {
  			InputStream istream = null;
  			OutputStream ostream = null;
  			try {
  				// Copy the requested stream. Stop if it exceeds MAX_SIZE
  				istream = url.openStream();
  				if (contentType != null) {
  					response.setContentType(contentType);
  				}
  				ostream = response.getOutputStream();
  
  				byte[] buffer = new byte[4096];
  				int length, totalLength = 0;
  				while ((totalLength < MAX_SIZE) && ((length = istream.read(buffer)) != -1)) {
  					ostream.write(buffer, 0, length);
  					totalLength += length;
  				}
  			} finally {
  				if (istream != null) {
  					istream.close();
  				}
  				if (ostream != null) {
  					ostream.close();
  				} else {
  					response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Cannot fetch: " + url.getProtocol());
  				}
  			}
  		}
  	}
  }