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.zookeeper.operations;
  
  import java.util.Arrays;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  
  import org.apache.zookeeper.WatchedEvent;
  import org.apache.zookeeper.Watcher;
  import org.apache.zookeeper.Watcher.Event.EventType;
  import org.apache.zookeeper.ZooKeeper;
  
  import static java.lang.String.format;
  
  /**
   * <code>FutureEventDrivenOperation</code> uses ZooKeepers {@link Watcher} mechanism to await specific ZooKeeper events.
   * Typically this is used to await changes to a particular node before retrieving the change.
   */
  public abstract class FutureEventDrivenOperation<ResultType> extends ZooKeeperOperation<ResultType>
          implements Watcher, WatchedEventProvider {
  
      private EventType[] awaitedTypes;
  
      private CountDownLatch waitForAnyWatchedType = new CountDownLatch(1);
  
      private WatchedEvent event;
  
      public FutureEventDrivenOperation(ZooKeeper connection, String node, EventType... awaitedTypes) {
          super(connection, node);
          this.awaitedTypes = awaitedTypes;
      }
  
      @Override
      public void process(WatchedEvent event) {
          this.event = event;
          EventType received = event.getType();
          if (LOG.isDebugEnabled()) {
              LOG.debug(format("Received event of type %s for node '%s'", received, event.getPath()));
          }
  
          for (EventType watched : awaitedTypes) {
              if (watched.equals(received)) {
                  result = getResult();
                  waitForAnyWatchedType.countDown();
              }
          }
  
          if (LOG.isTraceEnabled() && waitForAnyWatchedType.getCount() > 0) {
  
              LOG.trace(String.format("Received event of type %s did not match any watched types %s", received,
                      Arrays.toString(awaitedTypes)));
          }
      }
  
      @Override
      public OperationResult<ResultType> get() throws ExecutionException, InterruptedException {
          installWatch();
          waitingThreads.add(Thread.currentThread());
          waitForAnyWatchedType.await();
          return result;
      }
  
      @Override
      public OperationResult<ResultType> get(long timeout, TimeUnit unit)
              throws InterruptedException, ExecutionException, TimeoutException {
          installWatch();
          waitingThreads.add(Thread.currentThread());
          waitForAnyWatchedType.await(timeout, unit);
          return result;
      }
  
      /**
       * Install the watcher to receive {@link WatchedEvent}s. It should use the appropriate asynchronous ZooKeeper call
       * to do this so as not to block the route from starting. Once one of the watched for types of event is received a
       * call is made to getResult, which can use the appropriate synchronous call to retrieve the actual data.
       */
      protected abstract void installWatch();
  
      @Override
      public WatchedEvent getWatchedEvent() {
          return event;
      }
  
      public EventType[] getWatchedForTypes() {
          return awaitedTypes;
      }
  
  }
  