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 backtype.storm.windowing;
  
  import java.util.List;
  
  /**
   * A trigger policy that tracks event counts and sets the context for
   * eviction policy to evict based on latest watermark time.
   *
   * @param <T> the type of event tracked by this policy.
   */
  public class WatermarkCountTriggerPolicy<T> implements TriggerPolicy<T> {
      private final int count;
      private final TriggerHandler handler;
      private final EvictionPolicy<T> evictionPolicy;
      private final WindowManager<T> windowManager;
      private long lastProcessedTs = 0;
      private boolean started;
  
      public WatermarkCountTriggerPolicy(int count, TriggerHandler handler,
                                         EvictionPolicy<T> evictionPolicy, WindowManager<T> windowManager) {
          this.count = count;
          this.handler = handler;
          this.evictionPolicy = evictionPolicy;
          this.windowManager = windowManager;
          this.started = false;
      }
  
      @Override
      public void track(Event<T> event) {
          if (started && event.isWatermark()) {
              handleWaterMarkEvent(event);
          }
      }
  
      @Override
      public void reset() {
          // NOOP
      }
  
      @Override
      public void start() {
          started = true;
      }
  
      @Override
      public void shutdown() {
          // NOOP
      }
  
      /**
       * Triggers all the pending windows up to the waterMarkEvent timestamp
       * based on the sliding interval count.
       *
       * @param waterMarkEvent the watermark event
       */
      private void handleWaterMarkEvent(Event<T> waterMarkEvent) {
          long watermarkTs = waterMarkEvent.getTimestamp();
          List<Long> eventTs = windowManager.getSlidingCountTimestamps(lastProcessedTs, watermarkTs, count);
          for (long ts : eventTs) {
              evictionPolicy.setContext(ts);
              handler.onTrigger();
              lastProcessedTs = ts;
          }
      }
  
      @Override
      public String toString() {
          return "WatermarkCountTriggerPolicy{" +
                  "count=" + count +
                  ", lastProcessedTs=" + lastProcessedTs +
                  ", started=" + started +
                  '}';
      }
  }
  