/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.handler.codec.http.websocketx;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelFuture;
  import org.jboss.netty.channel.ChannelFutureListener;
  import org.jboss.netty.handler.codec.http.DefaultHttpResponse;
  import org.jboss.netty.handler.codec.http.HttpHeaders.Names;
  import org.jboss.netty.handler.codec.http.HttpRequest;
  import org.jboss.netty.handler.codec.http.HttpResponse;
  import org.jboss.netty.handler.codec.http.HttpResponseStatus;
  import org.jboss.netty.logging.InternalLogger;
  import org.jboss.netty.logging.InternalLoggerFactory;
  import org.jboss.netty.util.CharsetUtil;
  
  import static org.jboss.netty.handler.codec.http.HttpHeaders.Values.*;
  import static org.jboss.netty.handler.codec.http.HttpVersion.*;
  
  /**
   * <p>
   * Performs server side opening and closing handshakes for web socket specification version <a
   * href="http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-07" >draft-ietf-hybi-thewebsocketprotocol-
   * 07</a>
   * </p>
   */
  public class WebSocketServerHandshaker07 extends WebSocketServerHandshaker {
  
      private static final InternalLogger logger = InternalLoggerFactory.getInstance(WebSocketServerHandshaker07.class);
  
      public static final String WEBSOCKET_07_ACCEPT_GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
  
      private final boolean allowExtensions;
  
      /**
       * Constructor specifying the destination web socket location
       *
       * @param webSocketURL
       *            URL for web socket communications. e.g "ws://myhost.com/mypath".
       *            Subsequent web socket frames will be sent to this URL.
       * @param subprotocols
       *            CSV of supported protocols
       * @param allowExtensions
       *            Allow extensions to be used in the reserved bits of the web socket frame
       * @param maxFramePayloadLength
       *            Maximum allowable frame payload length. Setting this value to your application's
       *            requirement may reduce denial of service attacks using long data frames.
       */
      public WebSocketServerHandshaker07(
              String webSocketURL, String subprotocols, boolean allowExtensions, long maxFramePayloadLength) {
          super(WebSocketVersion.V07, webSocketURL, subprotocols, maxFramePayloadLength);
          this.allowExtensions = allowExtensions;
      }
  
      /**
       * <p>
       * Handle the web socket handshake for the web socket specification <a href=
       * "http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-07">HyBi version 7</a>.
       * </p>
       *
       * <p>
       * Browser request to the server:
       * </p>
       *
       * <pre>
       * GET /chat HTTP/1.1
       * Host: server.example.com
       * Upgrade: websocket
       * Connection: Upgrade
       * Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
       * Sec-WebSocket-Origin: http://example.com
       * Sec-WebSocket-Protocol: chat, superchat
       * Sec-WebSocket-Version: 7
       * </pre>
       *
       * <p>
       * Server response:
       * </p>
       *
       * <pre>
       * HTTP/1.1 101 Switching Protocols
       * Upgrade: websocket
       * Connection: Upgrade
       * Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
      * Sec-WebSocket-Protocol: chat
      * </pre>
      *
      * @param channel
      *            Channel
      * @param req
      *            HTTP request
      */
     @Override
     public ChannelFuture handshake(Channel channel, HttpRequest req) {
 
         if (logger.isDebugEnabled()) {
             logger.debug(String.format("Channel %s WS Version 7 server handshake", channel.getId()));
         }
         HttpResponse res = new DefaultHttpResponse(HTTP_1_1, HttpResponseStatus.SWITCHING_PROTOCOLS);
 
         String key = req.headers().get(Names.SEC_WEBSOCKET_KEY);
         if (key == null) {
             throw new WebSocketHandshakeException("not a WebSocket request: missing key");
         }
         String acceptSeed = key + WEBSOCKET_07_ACCEPT_GUID;
         ChannelBuffer sha1 = WebSocketUtil.sha1(ChannelBuffers.copiedBuffer(acceptSeed, CharsetUtil.US_ASCII));
         String accept = WebSocketUtil.base64(sha1);
 
         if (logger.isDebugEnabled()) {
             logger.debug(String.format("WS Version 7 Server Handshake key: %s. Response: %s.", key, accept));
         }
 
         res.setStatus(HttpResponseStatus.SWITCHING_PROTOCOLS);
         res.headers().add(Names.UPGRADE, WEBSOCKET.toLowerCase());
         res.headers().add(Names.CONNECTION, Names.UPGRADE);
         res.headers().add(Names.SEC_WEBSOCKET_ACCEPT, accept);
         String subprotocols = req.headers().get(Names.SEC_WEBSOCKET_PROTOCOL);
         if (subprotocols != null) {
             String selectedSubprotocol = selectSubprotocol(subprotocols);
             if (selectedSubprotocol == null) {
                 throw new WebSocketHandshakeException("Requested subprotocol(s) not supported: " + subprotocols);
             } else {
                 res.headers().add(Names.SEC_WEBSOCKET_PROTOCOL, selectedSubprotocol);
                 setSelectedSubprotocol(selectedSubprotocol);
             }
         }
 
         return writeHandshakeResponse(
                 channel, res, new WebSocket07FrameEncoder(false),
                               new WebSocket07FrameDecoder(true, allowExtensions, getMaxFramePayloadLength()));
     }
 
     /**
      * Echo back the closing frame and close the connection
      *
      * @param channel
      *            Channel
      * @param frame
      *            Web Socket frame that was received
      */
     @Override
     public ChannelFuture close(Channel channel, CloseWebSocketFrame frame) {
         ChannelFuture future = channel.write(frame);
         future.addListener(ChannelFutureListener.CLOSE);
         return future;
     }
 }