/*
    * 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.channel.Channel;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelPipeline;
  import io.netty.channel.ChannelPromise;
  import io.netty.channel.SimpleChannelInboundHandler;
  import io.netty.handler.codec.http.FullHttpRequest;
  import io.netty.handler.codec.http.FullHttpResponse;
  import io.netty.handler.codec.http.HttpContentCompressor;
  import io.netty.handler.codec.http.HttpHeaders;
  import io.netty.handler.codec.http.HttpObjectAggregator;
  import io.netty.handler.codec.http.HttpRequest;
  import io.netty.handler.codec.http.HttpRequestDecoder;
  import io.netty.handler.codec.http.HttpResponseEncoder;
  import io.netty.handler.codec.http.HttpServerCodec;
  import io.netty.util.ReferenceCountUtil;
  import io.netty.util.internal.EmptyArrays;
  import io.netty.util.internal.ThrowableUtil;
  import io.netty.util.internal.logging.InternalLogger;
  import io.netty.util.internal.logging.InternalLoggerFactory;
  
  import java.nio.channels.ClosedChannelException;
  import java.util.Collections;
  import java.util.LinkedHashSet;
  import java.util.Set;
  
  /**
   * Base class for server side web socket opening and closing handshakes
   */
  public abstract class WebSocketServerHandshaker {
      protected static final InternalLogger logger = InternalLoggerFactory.getInstance(WebSocketServerHandshaker.class);
      private static final ClosedChannelException CLOSED_CHANNEL_EXCEPTION = ThrowableUtil.unknownStackTrace(
              new ClosedChannelException(), WebSocketServerHandshaker.class, "handshake(...)");
  
      private final String uri;
  
      private final String[] subprotocols;
  
      private final WebSocketVersion version;
  
      private final int maxFramePayloadLength;
  
      private String selectedSubprotocol;
  
      /**
       * Use this as wildcard to support all requested sub-protocols
       */
      public static final String SUB_PROTOCOL_WILDCARD = "*";
  
      /**
       * Constructor specifying the destination web socket location
       *
       * @param version
       *            the protocol version
       * @param uri
       *            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. Null if sub protocols not supported.
       * @param maxFramePayloadLength
       *            Maximum length of a frame's payload
       */
      protected WebSocketServerHandshaker(
              WebSocketVersion version, String uri, String subprotocols,
              int maxFramePayloadLength) {
          this.version = version;
          this.uri = uri;
          if (subprotocols != null) {
              String[] subprotocolArray = subprotocols.split(",");
              for (int i = 0; i < subprotocolArray.length; i++) {
                  subprotocolArray[i] = subprotocolArray[i].trim();
              }
              this.subprotocols = subprotocolArray;
          } else {
              this.subprotocols = EmptyArrays.EMPTY_STRINGS;
          }
          this.maxFramePayloadLength = maxFramePayloadLength;
      }
  
      /**
       * Returns the URL of the web socket
      */
     public String uri() {
         return uri;
     }
 
     /**
      * Returns the CSV of supported sub protocols
      */
     public Set<String> subprotocols() {
         Set<String> ret = new LinkedHashSet<String>();
         Collections.addAll(ret, subprotocols);
         return ret;
     }
 
     /**
      * Returns the version of the specification being supported
      */
     public WebSocketVersion version() {
         return version;
     }
 
     /**
      * Gets the maximum length for any frame's payload.
      *
      * @return The maximum length for a frame's payload
      */
     public int maxFramePayloadLength() {
         return maxFramePayloadLength;
     }
 
     /**
      * Performs the opening handshake. When call this method you <strong>MUST NOT</strong> retain the
      * {@link FullHttpRequest} which is passed in.
      *
      * @param channel
      *              Channel
      * @param req
      *              HTTP Request
      * @return future
      *              The {@link ChannelFuture} which is notified once the opening handshake completes
      */
     public ChannelFuture handshake(Channel channel, FullHttpRequest req) {
         return handshake(channel, req, null, channel.newPromise());
     }
 
     /**
      * Performs the opening handshake
      *
      * When call this method you <strong>MUST NOT</strong> retain the {@link FullHttpRequest} which is passed in.
      *
      * @param channel
      *            Channel
      * @param req
      *            HTTP Request
      * @param responseHeaders
      *            Extra headers to add to the handshake response or {@code null} if no extra headers should be added
      * @param promise
      *            the {@link ChannelPromise} to be notified when the opening handshake is done
      * @return future
      *            the {@link ChannelFuture} which is notified when the opening handshake is done
      */
     public final ChannelFuture handshake(Channel channel, FullHttpRequest req,
                                             HttpHeaders responseHeaders, final ChannelPromise promise) {
 
         if (logger.isDebugEnabled()) {
             logger.debug("{} WebSocket version {} server handshake", channel, version());
         }
         FullHttpResponse response = newHandshakeResponse(req, responseHeaders);
         ChannelPipeline p = channel.pipeline();
         if (p.get(HttpObjectAggregator.class) != null) {
             p.remove(HttpObjectAggregator.class);
         }
         if (p.get(HttpContentCompressor.class) != null) {
             p.remove(HttpContentCompressor.class);
         }
         ChannelHandlerContext ctx = p.context(HttpRequestDecoder.class);
         final String encoderName;
         if (ctx == null) {
             // this means the user use a HttpServerCodec
             ctx = p.context(HttpServerCodec.class);
             if (ctx == null) {
                 promise.setFailure(
                         new IllegalStateException("No HttpDecoder and no HttpServerCodec in the pipeline"));
                 return promise;
             }
             p.addBefore(ctx.name(), "wsdecoder", newWebsocketDecoder());
             p.addBefore(ctx.name(), "wsencoder", newWebSocketEncoder());
             encoderName = ctx.name();
         } else {
             p.replace(ctx.name(), "wsdecoder", newWebsocketDecoder());
 
             encoderName = p.context(HttpResponseEncoder.class).name();
             p.addBefore(encoderName, "wsencoder", newWebSocketEncoder());
         }
         channel.writeAndFlush(response).addListener(new ChannelFutureListener() {
             @Override
             public void operationComplete(ChannelFuture future) throws Exception {
                 if (future.isSuccess()) {
                     ChannelPipeline p = future.channel().pipeline();
                     p.remove(encoderName);
                     promise.setSuccess();
                 } else {
                     promise.setFailure(future.cause());
                 }
             }
         });
         return promise;
     }
 
     /**
      * Performs the opening handshake. When call this method you <strong>MUST NOT</strong> retain the
      * {@link FullHttpRequest} which is passed in.
      *
      * @param channel
      *              Channel
      * @param req
      *              HTTP Request
      * @return future
      *              The {@link ChannelFuture} which is notified once the opening handshake completes
      */
     public ChannelFuture handshake(Channel channel, HttpRequest req) {
         return handshake(channel, req, null, channel.newPromise());
     }
 
     /**
      * Performs the opening handshake
      *
      * When call this method you <strong>MUST NOT</strong> retain the {@link HttpRequest} which is passed in.
      *
      * @param channel
      *            Channel
      * @param req
      *            HTTP Request
      * @param responseHeaders
      *            Extra headers to add to the handshake response or {@code null} if no extra headers should be added
      * @param promise
      *            the {@link ChannelPromise} to be notified when the opening handshake is done
      * @return future
      *            the {@link ChannelFuture} which is notified when the opening handshake is done
      */
     public final ChannelFuture handshake(final Channel channel, HttpRequest req,
                                          final HttpHeaders responseHeaders, final ChannelPromise promise) {
 
         if (req instanceof FullHttpRequest) {
             return handshake(channel, (FullHttpRequest) req, responseHeaders, promise);
         }
         if (logger.isDebugEnabled()) {
             logger.debug("{} WebSocket version {} server handshake", channel, version());
         }
         ChannelPipeline p = channel.pipeline();
         ChannelHandlerContext ctx = p.context(HttpRequestDecoder.class);
         if (ctx == null) {
             // this means the user use a HttpServerCodec
             ctx = p.context(HttpServerCodec.class);
             if (ctx == null) {
                 promise.setFailure(
                         new IllegalStateException("No HttpDecoder and no HttpServerCodec in the pipeline"));
                 return promise;
             }
         }
         // Add aggregator and ensure we feed the HttpRequest so it is aggregated. A limit o 8192 should be more then
         // enough for the websockets handshake payload.
         //
         // TODO: Make handshake work without HttpObjectAggregator at all.
         String aggregatorName = "httpAggregator";
         p.addAfter(ctx.name(), aggregatorName, new HttpObjectAggregator(8192));
         p.addAfter(aggregatorName, "handshaker", new SimpleChannelInboundHandler<FullHttpRequest>() {
             @Override
             protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest msg) throws Exception {
                 // Remove ourself and do the actual handshake
                 ctx.pipeline().remove(this);
                 handshake(channel, msg, responseHeaders, promise);
             }
 
             @Override
             public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
                 // Remove ourself and fail the handshake promise.
                 ctx.pipeline().remove(this);
                 promise.tryFailure(cause);
                 ctx.fireExceptionCaught(cause);
             }
 
             @Override
             public void channelInactive(ChannelHandlerContext ctx) throws Exception {
                 // Fail promise if Channel was closed
                 promise.tryFailure(CLOSED_CHANNEL_EXCEPTION);
                 ctx.fireChannelInactive();
             }
         });
         try {
             ctx.fireChannelRead(ReferenceCountUtil.retain(req));
         } catch (Throwable cause) {
             promise.setFailure(cause);
         }
         return promise;
     }
 
     /**
      * Returns a new {@link FullHttpResponse) which will be used for as response to the handshake request.
      */
     protected abstract FullHttpResponse newHandshakeResponse(FullHttpRequest req,
                                          HttpHeaders responseHeaders);
     /**
      * Performs the closing handshake
      *
      * @param channel
      *            Channel
      * @param frame
      *            Closing Frame that was received
      */
     public ChannelFuture close(Channel channel, CloseWebSocketFrame frame) {
         if (channel == null) {
             throw new NullPointerException("channel");
         }
         return close(channel, frame, channel.newPromise());
     }
 
     /**
      * Performs the closing handshake
      *
      * @param channel
      *            Channel
      * @param frame
      *            Closing Frame that was received
      * @param promise
      *            the {@link ChannelPromise} to be notified when the closing handshake is done
      */
     public ChannelFuture close(Channel channel, CloseWebSocketFrame frame, ChannelPromise promise) {
         if (channel == null) {
             throw new NullPointerException("channel");
         }
         return channel.writeAndFlush(frame, promise).addListener(ChannelFutureListener.CLOSE);
     }
 
     /**
      * Selects the first matching supported sub protocol
      *
      * @param requestedSubprotocols
      *            CSV of protocols to be supported. e.g. "chat, superchat"
      * @return First matching supported sub protocol. Null if not found.
      */
     protected String selectSubprotocol(String requestedSubprotocols) {
         if (requestedSubprotocols == null || subprotocols.length == 0) {
             return null;
         }
 
         String[] requestedSubprotocolArray = requestedSubprotocols.split(",");
         for (String p: requestedSubprotocolArray) {
             String requestedSubprotocol = p.trim();
 
             for (String supportedSubprotocol: subprotocols) {
                 if (SUB_PROTOCOL_WILDCARD.equals(supportedSubprotocol)
                         || requestedSubprotocol.equals(supportedSubprotocol)) {
                     selectedSubprotocol = requestedSubprotocol;
                     return requestedSubprotocol;
                 }
             }
         }
 
         // No match found
         return null;
     }
 
     /**
      * Returns the selected subprotocol. Null if no subprotocol has been selected.
      * <p>
      * This is only available AFTER <tt>handshake()</tt> has been called.
      * </p>
      */
     public String selectedSubprotocol() {
         return selectedSubprotocol;
     }
 
     /**
      * Returns the decoder to use after handshake is complete.
      */
     protected abstract WebSocketFrameDecoder newWebsocketDecoder();
 
     /**
      * Returns the encoder to use after the handshake is complete.
      */
     protected abstract WebSocketFrameEncoder newWebSocketEncoder();
 
 }