/**
 * 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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.storm.utils;

import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.LockSupport;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * This class implements time simulation support. When time simulation is enabled,
 * methods on this class will use fixed time. When time simulation is disabled,
 * methods will pass through to relevant java.lang.System/java.lang.Thread calls.
 * Methods using units higher than nanoseconds will pass through to System.currentTimeMillis().
 * Methods supporting nanoseconds will pass through to System.nanoTime().
 */
public final class Time {
  private static final Logger LOG = Logger.getLogger(Time.class.getName());
  private static final AtomicBoolean SIMULATING = new AtomicBoolean(false);
  private static final AtomicLong AUTO_ADVANCE_NANOS_ON_SLEEP = new AtomicLong(0);
  private static final Map<Thread, AtomicLong> THREAD_SLEEP_TIMES_NANOS = new ConcurrentHashMap<>();
  private static final Object SLEEP_TIMES_LOCK = new Object();
  private static final AtomicLong SIMULATED_CURR_TIME_NANOS = new AtomicLong(0);

  private Time() {
  }

  public static boolean isSimulating() {
    return SIMULATING.get();
  }

  public static void sleepUntil(long targetTimeMs) throws InterruptedException {
    if (SIMULATING.get()) {
      simulatedSleepUntilNanos(millisToNanos(targetTimeMs));
    } else {
      long sleepTimeMs = targetTimeMs - currentTimeMillis();
      if (sleepTimeMs > 0) {
        Thread.sleep(sleepTimeMs);
      }
    }
  }

  public static void sleepUntilNanos(long targetTimeNanos) throws InterruptedException {
    if (SIMULATING.get()) {
      simulatedSleepUntilNanos(targetTimeNanos);
    } else {
      long sleepTimeNanos = targetTimeNanos - nanoTime();
      long sleepTimeMs = nanosToMillis(sleepTimeNanos);
      int sleepTimeNanosSansMs = (int) (sleepTimeNanos % 1_000_000);
      if (sleepTimeNanos > 0) {
        Thread.sleep(sleepTimeMs, sleepTimeNanosSansMs);
      }
    }
  }

  private static void simulatedSleepUntilNanos(long targetTimeNanos) throws InterruptedException {
    try {
      synchronized (SLEEP_TIMES_LOCK) {
        if (!SIMULATING.get()) {
          LOG.log(Level.FINER, Thread.currentThread()
                  + " is still sleeping after simulated time disabled.",
              new RuntimeException("STACK TRACE"));
          throw new InterruptedException();
        }
        THREAD_SLEEP_TIMES_NANOS.put(Thread.currentThread(), new AtomicLong(targetTimeNanos));
      }
      while (SIMULATED_CURR_TIME_NANOS.get() < targetTimeNanos) {
        synchronized (SLEEP_TIMES_LOCK) {
          if (!SIMULATING.get()) {
            LOG.log(Level.FINER, Thread.currentThread()
                    + " is still sleeping after simulated time disabled.",
                new RuntimeException("STACK TRACE"));
            throw new InterruptedException();
          }
          long autoAdvance = AUTO_ADVANCE_NANOS_ON_SLEEP.get();
          if (autoAdvance > 0) {
            advanceTimeNanos(autoAdvance);
          }
        }
        Thread.sleep(10);
      }
    } finally {
      THREAD_SLEEP_TIMES_NANOS.remove(Thread.currentThread());
    }
  }

  public static void sleep(long ms) throws InterruptedException {
    if (ms > 0) {
      if (SIMULATING.get()) {
        simulatedSleepUntilNanos(millisToNanos(currentTimeMillis() + ms));
      } else {
        Thread.sleep(ms);
      }
    }
  }

  public static void parkNanos(long nanos) throws InterruptedException {
    if (nanos > 0) {
      if (SIMULATING.get()) {
        simulatedSleepUntilNanos(nanoTime() + nanos);
      } else {
        LockSupport.parkNanos(nanos);
      }
    }
  }

  public static void sleepSecs(long secs) throws InterruptedException {
    if (secs > 0) {
      sleep(secs * 1000);
    }
  }

  public static long nanoTime() {
    if (SIMULATING.get()) {
      return SIMULATED_CURR_TIME_NANOS.get();
    } else {
      return System.nanoTime();
    }
  }

  public static long currentTimeMillis() {
    if (SIMULATING.get()) {
      return nanosToMillis(SIMULATED_CURR_TIME_NANOS.get());
    } else {
      return System.currentTimeMillis();
    }
  }

  public static long nanosToMillis(long nanos) {
    return nanos / 1_000_000;
  }

  public static long millisToNanos(long millis) {
    return millis * 1_000_000;
  }

  public static long secsToMillis(int secs) {
    return 1000 * (long) secs;
  }

  public static long secsToMillisLong(double secs) {
    return (long) (1000 * secs);
  }

  public static int currentTimeSecs() {
    return (int) (currentTimeMillis() / 1000);
  }

  public static int deltaSecs(int timeInSeconds) {
    return Time.currentTimeSecs() - timeInSeconds;
  }

  public static long deltaMs(long timeInMilliseconds) {
    return Time.currentTimeMillis() - timeInMilliseconds;
  }

  public static void advanceTime(long ms) {
    advanceTimeNanos(millisToNanos(ms));
  }

  public static void advanceTimeNanos(long nanos) {
    if (!SIMULATING.get()) {
      throw new IllegalStateException("Cannot simulate time unless in simulation mode");
    }
    if (nanos < 0) {
      throw new IllegalArgumentException("advanceTime only accepts positive time as an argument");
    }
    synchronized (SLEEP_TIMES_LOCK) {
      long newTime = SIMULATED_CURR_TIME_NANOS.addAndGet(nanos);
      Iterator<AtomicLong> sleepTimesIter = THREAD_SLEEP_TIMES_NANOS.values().iterator();
      while (sleepTimesIter.hasNext()) {
        AtomicLong curr = sleepTimesIter.next();
        if (SIMULATED_CURR_TIME_NANOS.get() >= curr.get()) {
          sleepTimesIter.remove();
        }
      }
      LOG.log(Level.FINER, "Advanced simulated time to " + newTime);
    }
  }

  public static void advanceTimeSecs(long secs) {
    advanceTime(secs * 1_000);
  }

  public static boolean isThreadWaiting(Thread t) {
    if (!SIMULATING.get()) {
      throw new IllegalStateException("Must be in simulation mode");
    }
    AtomicLong time = THREAD_SLEEP_TIMES_NANOS.get(t);
    return !t.isAlive() || time != null && nanoTime() < time.longValue();
  }

  public static class SimulatedTime implements AutoCloseable {

    public SimulatedTime() {
      this(null);
    }

    public SimulatedTime(Number advanceTimeMs) {
      synchronized (Time.SLEEP_TIMES_LOCK) {
        Time.SIMULATING.set(true);
        Time.SIMULATED_CURR_TIME_NANOS.set(0);
        Time.THREAD_SLEEP_TIMES_NANOS.clear();
        if (advanceTimeMs != null) {
          Time.AUTO_ADVANCE_NANOS_ON_SLEEP.set(millisToNanos(advanceTimeMs.longValue()));
        } else {
          Time.AUTO_ADVANCE_NANOS_ON_SLEEP.set(0);
        }
        LOG.warning("AutoCloseable Simulated Time Starting...");
      }
    }

    @Override
    public void close() {
      synchronized (Time.SLEEP_TIMES_LOCK) {
        Time.SIMULATING.set(false);
        LOG.warning("AutoCloseable Simulated Time Ending...");
      }
    }
  }
}