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;
  
  import io.netty.channel.ChannelDuplexHandler;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.mqtt.MqttMessage;
  import io.netty.util.ReferenceCountUtil;
  import java.util.LinkedList;
  import java.util.Queue;
  
  public class MQTTMessageDebounceHandler extends ChannelDuplexHandler {
      public static final String NAME = "MQTTMessageDebounceHandler";
  
      private final Queue<MqttMessage> buffer = new LinkedList<>();
      private boolean readOne = false;
  
      @Override
      public void channelInactive(ChannelHandlerContext ctx) throws Exception {
          MqttMessage msg;
          while ((msg = buffer.poll()) != null) {
              ReferenceCountUtil.release(msg);
          }
          super.channelInactive(ctx);
      }
  
      @Override
      public void read(ChannelHandlerContext ctx) {
          if (ctx.channel().config().isAutoRead()) {
              MqttMessage msg;
              while ((msg = buffer.poll()) != null) {
                  ctx.fireChannelRead(msg);
              }
              ctx.read();
          } else {
              MqttMessage msg = buffer.poll();
              if (msg != null) {
                  ctx.fireChannelRead(msg);
              } else {
                  readOne = true;
                  ctx.read();
              }
          }
      }
  
      @Override
      public void channelRead(ChannelHandlerContext ctx, Object msg) {
          assert msg instanceof MqttMessage;
          if (ctx.channel().config().isAutoRead()) {
              ctx.fireChannelRead(msg);
          } else {
              buffer.offer((MqttMessage) msg);
              if (readOne) {
                  MqttMessage mqttMsg = buffer.poll();
                  ctx.fireChannelRead(mqttMsg);
                  readOne = false;
              }
          }
      }
  }
  