/*
    * 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 io.netty.handler.codec.http.websocketx;
  
  import io.netty.handler.codec.http.DefaultFullHttpResponse;
  import io.netty.handler.codec.http.FullHttpRequest;
  import io.netty.handler.codec.http.FullHttpResponse;
  import io.netty.handler.codec.http.HttpHeaders;
  import io.netty.handler.codec.http.HttpHeaders.Names;
  import io.netty.handler.codec.http.HttpResponseStatus;
  import io.netty.util.CharsetUtil;
  
  import static io.netty.handler.codec.http.HttpHeaders.Values.*;
  import static io.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-10" >draft-ietf-hybi-thewebsocketprotocol-
   * 10</a>
   * </p>
   */
  public class WebSocketServerHandshaker07 extends WebSocketServerHandshaker {
  
      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, int 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>
       */
      @Override
      protected FullHttpResponse newHandshakeResponse(FullHttpRequest req, HttpHeaders headers) {
  
          FullHttpResponse res =
                  new DefaultFullHttpResponse(HTTP_1_1, HttpResponseStatus.SWITCHING_PROTOCOLS);
 
         if (headers != null) {
             res.headers().add(headers);
         }
 
         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;
         byte[] sha1 = WebSocketUtil.sha1(acceptSeed.getBytes(CharsetUtil.US_ASCII));
         String accept = WebSocketUtil.base64(sha1);
 
         if (logger.isDebugEnabled()) {
             logger.debug("WebSocket version 07 server handshake key: {}, response: {}.", key, accept);
         }
 
         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) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("Requested subprotocol(s) not supported: {}", subprotocols);
                 }
             } else {
                 res.headers().add(Names.SEC_WEBSOCKET_PROTOCOL, selectedSubprotocol);
             }
         }
         return res;
     }
 
     @Override
     protected WebSocketFrameDecoder newWebsocketDecoder() {
         return new WebSocket07FrameDecoder(true, allowExtensions, maxFramePayloadLength());
     }
 
     @Override
     protected WebSocketFrameEncoder newWebSocketEncoder() {
         return new WebSocket07FrameEncoder(false);
     }
 }