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.camel.component.sjms.reply;
  
  import java.util.concurrent.ConcurrentSkipListSet;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.camel.TimeoutMap;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import static org.apache.camel.TimeoutMap.Listener.Type.*;
  
  /**
   * A creator which can build the JMS message selector query string to use with a shared reply-to queue, so we can select
   * the correct messages we expect as replies.
   */
  public class MessageSelectorCreator {
      protected static final Logger LOG = LoggerFactory.getLogger(MessageSelectorCreator.class);
      protected final TimeoutMap<String, ?> timeoutMap;
      protected final ConcurrentSkipListSet<String> correlationIds;
      private final Lock lock = new ReentrantLock();
      protected volatile boolean dirty = true;
      protected StringBuilder expression;
  
      public MessageSelectorCreator(CorrelationTimeoutMap timeoutMap) {
          this.timeoutMap = timeoutMap;
          this.timeoutMap.addListener((type, cid, value) -> timeoutEvent(type, cid));
          // create local set of correlation ids, as its easier to keep track
          // using the listener so we can flag the dirty flag upon changes
          // must support concurrent access
          this.correlationIds = new ConcurrentSkipListSet<>();
      }
  
      public String get() {
          lock.lock();
          try {
              if (!dirty) {
                  return expression.toString();
              }
  
              expression = new StringBuilder(256);
  
              expression.append("JMSCorrelationID='");
              if (correlationIds.isEmpty()) {
                  // no id's so use a dummy to select nothing
                  expression.append("CamelDummyJmsMessageSelector'");
              } else {
                  boolean first = true;
                  for (String value : correlationIds) {
                      if (!first) {
                          expression.append(" OR JMSCorrelationID='");
                      }
                      expression.append(value).append("'");
                      if (first) {
                          first = false;
                      }
                  }
              }
  
              String answer = expression.toString();
  
              dirty = false;
              return answer;
          } finally {
              lock.unlock();
          }
      }
  
      // Changes to live correlation-ids invalidate existing message selector
      private void timeoutEvent(TimeoutMap.Listener.Type type, String cid) {
          if (type == Put) {
              correlationIds.add(cid);
          } else if (type == Remove || type == Evict) {
              correlationIds.remove(cid);
          }
          dirty = true;
      }
  
  }
  