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/*
 * Copyright (c) 2007 through 2024 David Berkman
 *
 * This file is part of the SmallMind Code Project.
 *
 * The SmallMind Code Project is free software, you can redistribute
 * it and/or modify it under either, at your discretion...
 *
 * 1) The terms of GNU Affero General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at
 * your option) any later version.
 *
 * ...or...
 *
 * 2) The terms of the Apache License, Version 2.0.
 *
 * The SmallMind Code Project is distributed in the hope that it will
 * be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License or Apache License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * and the Apache License along with the SmallMind Code Project. If not, see
 *  or .
 *
 * Additional permission under the GNU Affero GPL version 3 section 7
 * ------------------------------------------------------------------
 * If you modify this Program, or any covered work, by linking or
 * combining it with other code, such other code is not for that reason
 * alone subject to any of the requirements of the GNU Affero GPL
 * version 3.
 */
package org.smallmind.claxon.registry.aggregate;

import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantLock;

public class Averaged implements Aggregate {

  private final ReentrantLock lock = new ReentrantLock();
  private final ConcurrentLinkedQueue valueQueue = new ConcurrentLinkedQueue<>();
  private final AtomicInteger size = new AtomicInteger();
  private long accumulatedValue;
  private int accumulatedCount;

  public void update (long value) {

    if (lock.tryLock()) {
      try {
        sweep();

        accumulatedValue += value;
        accumulatedCount++;
      } finally {
        lock.unlock();
      }
    } else {
      size.incrementAndGet();
      valueQueue.add(value);
    }
  }

  public void sweep () {

    int cap = size.get();
    int n = 0;

    if (cap > 0) {

      Long unprocessed;

      while ((unprocessed = valueQueue.poll()) != null) {
        size.decrementAndGet();
        accumulatedValue += unprocessed;
        accumulatedCount++;
        if (++n >= cap) {
          break;
        }
      }
    }
  }

  public double getAverage () {

    lock.lock();
    try {

      double average;

      sweep();

      average = accumulatedValue / ((double)accumulatedCount);

      accumulatedValue = 0;
      accumulatedCount = 0;

      return average;
    } finally {
      lock.unlock();
    }
  }
}