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.beam.runners.dataflow.worker.util.common.worker;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.LinkedHashMap;
  import java.util.List;
  
  /**
   * Receiver that forwards each input it receives to each of a list of output Receivers.
   * Additionally, it invokes output counters who track size information for elements passing through.
   */
  public class OutputReceiver implements Receiver {
    private final List<Receiver> outputs = new ArrayList<>();
    private final HashMap<String, ElementCounter> outputCounters = new LinkedHashMap<>();
  
    /** Adds a new receiver that this OutputReceiver forwards to. */
    public void addOutput(Receiver receiver) {
      outputs.add(receiver);
    }
  
    public void addOutputCounter(ElementCounter outputCounter) {
      outputCounters.put(Integer.toString(outputCounters.size()), outputCounter);
    }
  
    public void addOutputCounter(String counterName, ElementCounter outputCounter) {
      outputCounters.put(counterName, outputCounter);
    }
  
    @Override
    public void process(Object elem) throws Exception {
      for (ElementCounter counter : outputCounters.values()) {
        counter.update(elem);
      }
  
      // Fan-out.
      for (Receiver out : outputs) {
        if (out != null) {
          out.process(elem);
        }
      }
  
      for (ElementCounter counter : outputCounters.values()) {
        counter.finishLazyUpdate(elem);
      }
    }
  
    public HashMap<String, ElementCounter> getOutputCounters() {
      return this.outputCounters;
    }
  
    /** Invoked by tests only. */
    public int getReceiverCount() {
      return outputs.size();
    }
  
    /** Invoked by tests only. */
    public Receiver getOnlyReceiver() {
      if (outputs.size() != 1) {
        throw new AssertionError("only one receiver expected");
      }
  
      return outputs.get(0);
    }
  }
  