/*
    * 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.giraph.utils;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Makes a list of {@link ProgressCounter} accessible through
   * a {@link ThreadLocal}.
   */
  public class ThreadLocalProgressCounter extends ThreadLocal<ProgressCounter> {
    /**
     * List of counters.
     */
    private final List<ProgressCounter> counters = new ArrayList<>();
  
    /**
     * Initializes a new counter, adds it to the list of counters
     * and returns it.
     * @return Progress counter.
     */
    @Override
    protected ProgressCounter initialValue() {
      ProgressCounter threadCounter = new ProgressCounter();
      synchronized (counters) {
        counters.add(threadCounter);
      }
      return threadCounter;
    }
  
    /**
     * Sums the progress of all counters.
     * @return Sum of all counters
     */
    public long getProgress() {
      long progress = 0;
      synchronized (counters) {
        for (ProgressCounter entry : counters) {
          progress += entry.getValue();
        }
      }
      return progress;
    }
  
    /**
     * Removes all counters.
     */
    public void reset() {
      counters.clear();
    }
  }