/*
    * Copyright 2019 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.ChannelFuture;
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelInboundHandlerAdapter;
  import io.netty.channel.ChannelPipeline;
  import io.netty.channel.ChannelPromise;
  import io.netty.handler.codec.http.DefaultFullHttpResponse;
  import io.netty.handler.codec.http.FullHttpRequest;
  import io.netty.handler.codec.http.HttpHeaderNames;
  import io.netty.handler.codec.http.HttpRequest;
  import io.netty.handler.codec.http.HttpResponse;
  import io.netty.handler.codec.http.websocketx.WebSocketServerProtocolHandler.ServerHandshakeStateEvent;
  import io.netty.handler.ssl.SslHandler;
  import io.netty.util.concurrent.Future;
  import io.netty.util.concurrent.FutureListener;
  
  import java.util.concurrent.TimeUnit;
  
  import static io.netty.handler.codec.http.HttpMethod.*;
  import static io.netty.handler.codec.http.HttpResponseStatus.*;
  import static io.netty.handler.codec.http.HttpUtil.*;
  import static io.netty.handler.codec.http.HttpVersion.*;
  import static io.netty.util.internal.ObjectUtil.*;
  
  /**
   * Handles the HTTP handshake (the HTTP Upgrade request) for {@link WebSocketServerProtocolHandler}.
   */
  class WebSocketServerProtocolHandshakeHandler extends ChannelInboundHandlerAdapter {
  
      private final WebSocketServerProtocolConfig serverConfig;
      private ChannelHandlerContext ctx;
      private ChannelPromise handshakePromise;
  
      WebSocketServerProtocolHandshakeHandler(WebSocketServerProtocolConfig serverConfig) {
          this.serverConfig = checkNotNull(serverConfig, "serverConfig");
      }
  
      @Override
      public void handlerAdded(ChannelHandlerContext ctx) {
          this.ctx = ctx;
          handshakePromise = ctx.newPromise();
      }
  
      @Override
      public void channelRead(final ChannelHandlerContext ctx, Object msg) throws Exception {
          final FullHttpRequest req = (FullHttpRequest) msg;
          if (isNotWebSocketPath(req)) {
              ctx.fireChannelRead(msg);
              return;
          }
  
          try {
              if (!GET.equals(req.method())) {
                  sendHttpResponse(ctx, req, new DefaultFullHttpResponse(HTTP_1_1, FORBIDDEN, ctx.alloc().buffer(0)));
                  return;
              }
  
              final WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
                      getWebSocketLocation(ctx.pipeline(), req, serverConfig.websocketPath()),
                      serverConfig.subprotocols(), serverConfig.decoderConfig());
              final WebSocketServerHandshaker handshaker = wsFactory.newHandshaker(req);
              final ChannelPromise localHandshakePromise = handshakePromise;
              if (handshaker == null) {
                  WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
              } else {
                  // Ensure we set the handshaker and replace this handler before we
                  // trigger the actual handshake. Otherwise we may receive websocket bytes in this handler
                  // before we had a chance to replace it.
                  //
                  // See https://github.com/netty/netty/issues/9471.
                  WebSocketServerProtocolHandler.setHandshaker(ctx.channel(), handshaker);
                  ctx.pipeline().remove(this);
  
                  final ChannelFuture handshakeFuture = handshaker.handshake(ctx.channel(), req);
                  handshakeFuture.addListener(new ChannelFutureListener() {
                      @Override
                      public void operationComplete(ChannelFuture future) {
                          if (!future.isSuccess()) {
                              localHandshakePromise.tryFailure(future.cause());
                              ctx.fireExceptionCaught(future.cause());
                          } else {
                              localHandshakePromise.trySuccess();
                             // Kept for compatibility
                             ctx.fireUserEventTriggered(
                                     WebSocketServerProtocolHandler.ServerHandshakeStateEvent.HANDSHAKE_COMPLETE);
                             ctx.fireUserEventTriggered(
                                     new WebSocketServerProtocolHandler.HandshakeComplete(
                                             req.uri(), req.headers(), handshaker.selectedSubprotocol()));
                         }
                     }
                 });
                 applyHandshakeTimeout();
             }
         } finally {
             req.release();
         }
     }
 
     private boolean isNotWebSocketPath(FullHttpRequest req) {
         String websocketPath = serverConfig.websocketPath();
         return serverConfig.checkStartsWith() ? !req.uri().startsWith(websocketPath) : !req.uri().equals(websocketPath);
     }
 
     private static void sendHttpResponse(ChannelHandlerContext ctx, HttpRequest req, HttpResponse res) {
         ChannelFuture f = ctx.channel().writeAndFlush(res);
         if (!isKeepAlive(req) || res.status().code() != 200) {
             f.addListener(ChannelFutureListener.CLOSE);
         }
     }
 
     private static String getWebSocketLocation(ChannelPipeline cp, HttpRequest req, String path) {
         String protocol = "ws";
         if (cp.get(SslHandler.class) != null) {
             // SSL in use so use Secure WebSockets
             protocol = "wss";
         }
         String host = req.headers().get(HttpHeaderNames.HOST);
         return protocol + "://" + host + path;
     }
 
     private void applyHandshakeTimeout() {
         final ChannelPromise localHandshakePromise = handshakePromise;
         final long handshakeTimeoutMillis = serverConfig.handshakeTimeoutMillis();
         if (handshakeTimeoutMillis <= 0 || localHandshakePromise.isDone()) {
             return;
         }
 
         final Future<?> timeoutFuture = ctx.executor().schedule(new Runnable() {
             @Override
             public void run() {
                 if (!localHandshakePromise.isDone() &&
                         localHandshakePromise.tryFailure(new WebSocketHandshakeException("handshake timed out"))) {
                     ctx.flush()
                        .fireUserEventTriggered(ServerHandshakeStateEvent.HANDSHAKE_TIMEOUT)
                        .close();
                 }
             }
         }, handshakeTimeoutMillis, TimeUnit.MILLISECONDS);
 
         // Cancel the handshake timeout when handshake is finished.
         localHandshakePromise.addListener(new FutureListener<Void>() {
             @Override
             public void operationComplete(Future<Void> f) {
                 timeoutFuture.cancel(false);
             }
         });
     }
 }