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.activemq.transport.mqtt;
  
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  
  import org.apache.activemq.Service;
  import org.apache.activemq.broker.BrokerService;
  import org.apache.activemq.command.ActiveMQMessage;
  import org.apache.activemq.util.LRUCache;
  import org.apache.activemq.util.ServiceStopper;
  import org.apache.activemq.util.ServiceSupport;
  import org.fusesource.mqtt.codec.PUBLISH;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Manages PUBLISH packet ids for clients.
   *
   * @author Dhiraj Bokde
   */
  public class MQTTPacketIdGenerator extends ServiceSupport {
  
      private static final Logger LOG = LoggerFactory.getLogger(MQTTPacketIdGenerator.class);
      private static final Object LOCK = new Object();
  
      Map<String, PacketIdMaps> clientIdMap = new ConcurrentHashMap<String, PacketIdMaps>();
  
      private final NonZeroSequenceGenerator messageIdGenerator = new NonZeroSequenceGenerator();
  
      private MQTTPacketIdGenerator() {
      }
  
      @Override
      protected void doStop(ServiceStopper stopper) throws Exception {
          synchronized (this) {
              clientIdMap = new ConcurrentHashMap<String, PacketIdMaps>();
          }
      }
  
      @Override
      protected void doStart() throws Exception {
      }
  
      public void startClientSession(String clientId) {
          if (!clientIdMap.containsKey(clientId)) {
              clientIdMap.put(clientId, new PacketIdMaps());
          }
      }
  
      public boolean stopClientSession(String clientId) {
          return clientIdMap.remove(clientId) != null;
      }
  
      public short setPacketId(String clientId, MQTTSubscription subscription, ActiveMQMessage message, PUBLISH publish) {
          final PacketIdMaps idMaps = clientIdMap.get(clientId);
          if (idMaps == null) {
              // maybe its a cleansession=true client id, use session less message id
              final short id = messageIdGenerator.getNextSequenceId();
              publish.messageId(id);
              return id;
          } else {
              return idMaps.setPacketId(subscription, message, publish);
          }
      }
  
      public void ackPacketId(String clientId, short packetId) {
          final PacketIdMaps idMaps = clientIdMap.get(clientId);
          if (idMaps != null) {
              idMaps.ackPacketId(packetId);
          }
      }
  
      public short getNextSequenceId(String clientId) {
          final PacketIdMaps idMaps = clientIdMap.get(clientId);
          return idMaps != null ? idMaps.getNextSequenceId(): messageIdGenerator.getNextSequenceId();
      }
  
      public static MQTTPacketIdGenerator getMQTTPacketIdGenerator(BrokerService broker) {
          MQTTPacketIdGenerator result = null;
          if (broker != null) {
              synchronized (LOCK) {
                  Service[] services = broker.getServices();
                  if (services != null) {
                      for (Service service : services) {
                          if (service instanceof MQTTPacketIdGenerator) {
                              return (MQTTPacketIdGenerator) service;
                          }
                      }
                  }
                  result = new MQTTPacketIdGenerator();
                  broker.addService(result);
                  if (broker.isStarted()) {
                      try {
                          result.start();
                      } catch (Exception e) {
                          LOG.warn("Couldn't start MQTTPacketIdGenerator");
                      }
                  }
              }
          }
  
  
          return result;
      }
  
      private class PacketIdMaps {
  
          private final NonZeroSequenceGenerator messageIdGenerator = new NonZeroSequenceGenerator();
          final Map<String, Short> activemqToPacketIds = new LRUCache<String, Short>(MQTTProtocolConverter.DEFAULT_CACHE_SIZE);
          final Map<Short, String> packetIdsToActivemq = new LRUCache<Short, String>(MQTTProtocolConverter.DEFAULT_CACHE_SIZE);
  
          short setPacketId(MQTTSubscription subscription, ActiveMQMessage message, PUBLISH publish) {
              // subscription key
              final StringBuilder subscriptionKey = new StringBuilder();
              subscriptionKey.append(subscription.getConsumerInfo().getDestination().getPhysicalName())
                  .append(':').append(message.getJMSMessageID());
              final String keyStr = subscriptionKey.toString();
              Short packetId;
              synchronized (activemqToPacketIds) {
                  packetId = activemqToPacketIds.get(keyStr);
                  if (packetId == null) {
                      packetId = getNextSequenceId();
                      activemqToPacketIds.put(keyStr, packetId);
                      packetIdsToActivemq.put(packetId, keyStr);
                  } else {
                      // mark publish as duplicate!
                      publish.dup(true);
                  }
              }
              publish.messageId(packetId);
              return packetId;
          }
  
          void ackPacketId(short packetId) {
              synchronized (activemqToPacketIds) {
                  final String subscriptionKey = packetIdsToActivemq.remove(packetId);
                  if (subscriptionKey != null) {
                      activemqToPacketIds.remove(subscriptionKey);
                  }
              }
          }
  
          short getNextSequenceId() {
              return messageIdGenerator.getNextSequenceId();
          }
  
      }
  
      private class NonZeroSequenceGenerator {
  
          private short lastSequenceId;
  
          public synchronized short getNextSequenceId() {
              final short val = ++lastSequenceId;
              return val != 0 ? val : ++lastSequenceId;
          }
  
      }
  
  }
  