content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.apache.bifromq.mqtt.handler.ws;
  
  import io.netty.channel.ChannelFutureListener;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.SimpleChannelInboundHandler;
  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.HttpHeaderNames;
  import io.netty.handler.codec.http.HttpResponseStatus;
  import io.netty.util.ReferenceCountUtil;
  
  /**
   * A simple handler that rejects all requests that are not WebSocket upgrade requests.
   */
  public class WebSocketOnlyHandler extends SimpleChannelInboundHandler<FullHttpRequest> {
      private final String websocketPath;
  
      public WebSocketOnlyHandler(String websocketPath) {
          super(false);
          this.websocketPath = websocketPath;
      }
  
      @Override
      protected void channelRead0(ChannelHandlerContext ctx, FullHttpRequest req) {
          if (!req.uri().equals(websocketPath)
              ||
              !req.headers().get(HttpHeaderNames.UPGRADE, "").equalsIgnoreCase("websocket")) {
              FullHttpResponse response =
                  new DefaultFullHttpResponse(req.protocolVersion(), HttpResponseStatus.BAD_REQUEST);
              ReferenceCountUtil.release(req);
              ctx.writeAndFlush(response).addListener(ChannelFutureListener.CLOSE);
          } else {
              // Proceed with the pipeline setup for WebSocket.
              ctx.pipeline().remove(this); // Remove the validator after it's used.
              ctx.fireChannelRead(req); // Pass the request further if it's valid.
          }
      }
  }
  