/*******************************************************************************
 * Copyright (C) 2015 Google Inc.
 *
 * Licensed 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 com.google.cloud.dataflow.sdk.util.common.worker;

import java.util.ArrayList;
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 List<ElementCounter> outputCounters = new ArrayList<>();

  /**
   * Adds a new receiver that this OutputReceiver forwards to.
   */
  public void addOutput(Receiver receiver) {
    outputs.add(receiver);
  }

  public void addOutputCounter(ElementCounter outputCounter) {
    outputCounters.add(outputCounter);
  }


  @Override
  public void process(Object elem) throws Exception {
    for (ElementCounter counter : outputCounters) {
      counter.update(elem);
    }

    // Fan-out.
    for (Receiver out : outputs) {
      if (out != null) {
        out.process(elem);
      }
    }

    for (ElementCounter counter : outputCounters) {
      counter.finishLazyUpdate(elem);
    }
  }

  /** 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);
  }
}
