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.partition;
  
  import backtype.storm.generated.GlobalStreamId;
  import backtype.storm.grouping.CustomStreamGrouping;
  import backtype.storm.task.WorkerTopologyContext;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  public class IdentityGrouping implements CustomStreamGrouping {
  
      List<Integer> ret = new ArrayList<Integer>();
      Map<Integer, List<Integer>> _precomputed = new HashMap();
  
      @Override
      public void prepare(WorkerTopologyContext context, GlobalStreamId stream, List<Integer> tasks) {
          List<Integer> sourceTasks = new ArrayList<Integer>(context.getComponentTasks(stream.get_componentId()));
          Collections.sort(sourceTasks);
          if (sourceTasks.size() != tasks.size()) {
              throw new RuntimeException("Can only do an identity grouping when source and target have same number of tasks");
          }
          tasks = new ArrayList<Integer>(tasks);
          Collections.sort(tasks);
          for (int i = 0; i < sourceTasks.size(); i++) {
              int s = sourceTasks.get(i);
              int t = tasks.get(i);
              _precomputed.put(s, Arrays.asList(t));
          }
      }
  
      @Override
      public List<Integer> chooseTasks(int task, List<Object> values) {
          List<Integer> ret = _precomputed.get(task);
          if (ret == null) {
              throw new RuntimeException("Tuple emitted by task that's not part of this component. Should be impossible");
          }
          return ret;
      }
  
  }
  