/*
 * 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.hadoop.hdds.utils;

import org.apache.ratis.util.function.CheckedRunnable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

/**
 * This class encapsulates ScheduledExecutorService.
 */
public class Scheduler {

  private static final Logger LOG =
      LoggerFactory.getLogger(Scheduler.class);

  private ScheduledExecutorService scheduler;

  private volatile boolean isClosed;

  private String threadName;

  /**
   * Creates a ScheduledExecutorService based on input arguments.
   * @param threadName - thread name
   * @param isDaemon - if true the threads in the scheduler are started as
   *                 daemon
   * @param numCoreThreads - number of core threads to maintain in the scheduler
   */
  public Scheduler(String threadName, boolean isDaemon, int numCoreThreads) {
    scheduler = Executors.newScheduledThreadPool(numCoreThreads, r -> {
      Thread t = new Thread(r);
      t.setName(threadName);
      t.setDaemon(isDaemon);
      return t;
    });
    this.threadName = threadName;
    isClosed = false;
  }

  public void schedule(Runnable runnable, long delay, TimeUnit timeUnit) {
    scheduler.schedule(runnable, delay, timeUnit);
  }

  public void schedule(CheckedRunnable runnable, long delay,
      TimeUnit timeUnit, Logger logger, String errMsg) {
    scheduler.schedule(() -> {
      try {
        runnable.run();
      } catch (Throwable throwable) {
        logger.error(errMsg, throwable);
      }
    }, delay, timeUnit);
  }

  public void scheduleWithFixedDelay(Runnable runnable, long initialDelay,
      long fixedDelay, TimeUnit timeUnit) {
    scheduler
        .scheduleWithFixedDelay(runnable, initialDelay, fixedDelay, timeUnit);
  }

  public boolean isClosed() {
    return isClosed;
  }

  /**
   * Closes the scheduler for further task submission. Any pending tasks not
   * yet executed are also cancelled. For the executing tasks the scheduler
   * waits 60 seconds for completion.
   */
  public synchronized void close() {
    isClosed = true;
    if (scheduler != null) {
      scheduler.shutdownNow();
      try {
        scheduler.awaitTermination(60, TimeUnit.SECONDS);
      } catch (InterruptedException e) {
        LOG.info(
            threadName + " interrupted while waiting for task completion {}",
            e);
      }
    }
    scheduler = null;
  }
}