package org.example;

import org.openjdk.jmh.annotations.*;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class LockTest {

  private static final Object intrinsicLock = new Object();
  private static final Lock explicitLock = new ReentrantLock(false);
  private static int seed = 0;

  @Benchmark
  @Measurement(iterations = 3)
  @Threads(10)
  @Fork(1)
  @Warmup(iterations = 5, time = 10)
  public long testWithoutLock() {
    return doSomething(100);
  }

  @Benchmark
  @Measurement(iterations = 3)
  @Threads(10)
  @Fork(1)
  @Warmup(iterations = 5, time = 10)
  public long testReentrantLock() {
    explicitLock.lock();
    try {
      return doSomething(100);
    } finally {
      explicitLock.unlock();
    }
  }

  @Benchmark
  @Measurement(iterations = 3)
  @Threads(10)
  @Fork(1)
  @Warmup(iterations = 5, time = 10)
  public long testSynchronized() {
    synchronized (intrinsicLock) {
      return doSomething(100);
    }
  }

  static int calculateNext(int y) {
    y ^= (y << 6);
    y ^= (y >>> 21);
    y ^= (y << 7);
    return y;
  }

  private long doSomething(int n) {
    int s = seed;
    seed = calculateNext(s);
    int remainder = s % n;
    return remainder > 0 ? remainder : remainder + n;
  }
}