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 storm.trident.operation.impl;
  
  import java.io.Serializable;
  import java.util.Map;
  import storm.trident.operation.Aggregator;
  import storm.trident.operation.TridentCollector;
  import storm.trident.operation.TridentOperationContext;
  import storm.trident.operation.impl.SingleEmitAggregator.SingleEmitState;
  import storm.trident.tuple.TridentTuple;
  
  public class SingleEmitAggregator implements Aggregator<SingleEmitState> {
      public static interface BatchToPartition extends Serializable {
          int partitionIndex(Object batchId, int numPartitions);
      }
  
      static class SingleEmitState {
          boolean received = false;
          Object state;
          Object batchId;
  
          public SingleEmitState(Object batchId) {
              this.batchId = batchId;
          }
      }
  
      Aggregator _agg;
      BatchToPartition _batchToPartition;
  
      public SingleEmitAggregator(Aggregator agg, BatchToPartition batchToPartition) {
          _agg = agg;
          _batchToPartition = batchToPartition;
      }
  
      @Override
      public SingleEmitState init(Object batchId, TridentCollector collector) {
          return new SingleEmitState(batchId);
      }
  
      @Override
      public void aggregate(SingleEmitState val, TridentTuple tuple, TridentCollector collector) {
          if (!val.received) {
              val.state = _agg.init(val.batchId, collector);
              val.received = true;
          }
          _agg.aggregate(val.state, tuple, collector);
      }
  
      @Override
      public void complete(SingleEmitState val, TridentCollector collector) {
          if (!val.received) {
              if (this.myPartitionIndex == _batchToPartition.partitionIndex(val.batchId, this.totalPartitions)) {
                  val.state = _agg.init(val.batchId, collector);
                  _agg.complete(val.state, collector);
              }
          } else {
              _agg.complete(val.state, collector);
          }
      }
  
      int myPartitionIndex;
      int totalPartitions;
  
      @Override
      public void prepare(Map conf, TridentOperationContext context) {
          _agg.prepare(conf, context);
          this.myPartitionIndex = context.getPartitionIndex();
          this.totalPartitions = context.numPartitions();
      }
  
      @Override
      public void cleanup() {
          _agg.cleanup();
      }
  
  }
  