/*
    * 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
    *
    *      https://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.commons.logging;
  
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  // after: https://github.com/apache/logging-log4j2/blob/c47e98423b461731f7791fcb9ea1079cd451f365/log4j-core/src/test/java/org/apache/logging/log4j/core/GarbageCollectionHelper.java
  public final class GarbageCollectionHelper implements Closeable, Runnable {
  
      final class GcTask implements Runnable {
          @Override
          public void run() {
              try {
                  while (running.get()) {
                      // Allocate data to help suggest a GC
                      try {
                          // 1mb of heap
                          final byte[] buf = new byte[1024 * 1024];
                          SINK.write(buf);
                      } catch (final IOException ignored) {
                      }
                      // May no-op depending on the JVM configuration
                      System.gc();
                  }
              } finally {
                  latch.countDown();
              }
          }
      }
      private static final OutputStream SINK = new OutputStream() {
          @Override
          public void write(final byte[] b) {
          }
  
          @Override
          public void write(final byte[] b, final int off, final int len) {
          }
  
          @Override
          public void write(final int b) {
          }
      };
  
      private final AtomicBoolean running = new AtomicBoolean();
      private final CountDownLatch latch = new CountDownLatch(1);
      private final Thread gcThread = new Thread(new GcTask());
  
      @Override
      public void close() {
          running.set(false);
          try {
              assertTrue(latch.await(10, TimeUnit.SECONDS), "GarbageCollectionHelper did not shut down cleanly");
          } catch (final InterruptedException e) {
              Thread.currentThread().interrupt();
              throw new RuntimeException(e);
          }
      }
  
      @Override
      public void run() {
          if (running.compareAndSet(false, true)) {
              gcThread.start();
          }
      }
  }