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.v5;
  
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Optional;
  
  public class ReceiverTopicAliasManager {
      private final Map<String, Integer> topicToAlias = new HashMap<>();
      private final Map<Integer, String> aliasToTopic = new HashMap<>();
  
      public Optional<String> getTopic(int alias) {
          return Optional.ofNullable(aliasToTopic.get(alias));
      }
  
      public Optional<Integer> getAlias(String topic) {
          return Optional.ofNullable(topicToAlias.get(topic));
      }
  
      public void setAlias(String topic, int alias) {
          Integer oldAlias = topicToAlias.put(topic, alias);
          if (oldAlias != null) {
              aliasToTopic.remove(oldAlias);
          }
          String oldTopic = aliasToTopic.put(alias, topic);
          if (oldTopic != null) {
              topicToAlias.remove(oldTopic);
          }
      }
  }
  