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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.swing.memory;

import java.util.Iterator;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import org.smallmind.nutsnbolts.util.WeakEventListenerList;
import org.smallmind.scribe.pen.LoggerManager;

public class MemoryTimer implements java.lang.Runnable {

  private static final String[] scalingTitles = {" bytes", "k", "M", "G", "T", "P", "E"};
  private static final long pulseTime = 3000;

  private final CountDownLatch exitLatch;
  private final CountDownLatch pulseLatch;
  private final AtomicBoolean finished = new AtomicBoolean(false);
  private final WeakEventListenerList listenerList;

  public MemoryTimer () {

    listenerList = new WeakEventListenerList();

    pulseLatch = new CountDownLatch(1);
    exitLatch = new CountDownLatch(1);
  }

  public synchronized void addMemoryUsageListener (MemoryUsageListener memoryUsageListener) {

    listenerList.addListener(memoryUsageListener);
  }

  public synchronized void removeMemoryUsageListener (MemoryUsageListener memoryUsageListener) {

    listenerList.removeListener(memoryUsageListener);
  }

  public void finish ()
    throws InterruptedException {

    if (finished.compareAndSet(false, true)) {
      pulseLatch.countDown();
    }

    exitLatch.await();
  }

  public void run () {

    Runtime runtime;
    long totalMemory;
    long freeMemory;
    long usedMemory;
    int scalingFactor;
    int scalingUnit;
    int maximumUsage;
    int currentUsage;

    runtime = Runtime.getRuntime();

    try {
      while (!finished.get()) {
        totalMemory = runtime.totalMemory();
        freeMemory = runtime.freeMemory();
        usedMemory = totalMemory - freeMemory;

        scalingFactor = 1;
        scalingUnit = 0;

        while ((usedMemory / scalingFactor) >= 1024) {
          scalingFactor *= 1024;
          scalingUnit++;
        }

        if ((scalingUnit > 0) && ((usedMemory / scalingFactor) == (totalMemory / scalingFactor))) {
          scalingFactor /= 1024;
          scalingUnit--;
        }

        maximumUsage = (int)(totalMemory / scalingFactor);
        currentUsage = (int)(usedMemory / scalingFactor);

        fireMemoryUsageUpdate(maximumUsage, currentUsage, currentUsage + scalingTitles[scalingUnit] + " of " + maximumUsage + scalingTitles[scalingUnit]);

        try {
          pulseLatch.await(pulseTime, TimeUnit.MILLISECONDS);
        } catch (InterruptedException interruptedException) {
          LoggerManager.getLogger(MemoryTimer.class).error(interruptedException);
        }
      }
    } finally {
      exitLatch.countDown();
    }
  }

  private void fireMemoryUsageUpdate (int maximumUsage, int currentUsage, String displayUsage) {

    Iterator listenerIter = listenerList.getListeners();
    MemoryUsageEvent memoryUsageEvent;

    memoryUsageEvent = new MemoryUsageEvent(this, maximumUsage, currentUsage, displayUsage);
    while (listenerIter.hasNext()) {
      listenerIter.next().usageUpdate(memoryUsageEvent);
    }
  }
}