package org.warp.commonutils.locks;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

public class TransitLockTest {

	@Test
	public void testTransit() {
		var lock = new TransitLock();
		lock.transit();
		lock.transit();
		lock.transit();
	}

	@Test
	public void testPartialTransit() {
		var lock = new TransitLock();
		lock.startTransit();
		lock.endTransit();
		lock.startTransit();
		lock.endTransit();
		lock.startTransit();
		lock.endTransit();
	}

	@Test
	public void testAllowTransit() {
		var lock = new TransitLock();
		lock.disallowTransit();
		lock.allowTransit();
		lock.transit();
	}

	@Test
	public void testMultiAllowTransit() {
		Assertions.assertThrows(IllegalStateException.class, () -> {
			var lock = new TransitLock();
			lock.allowTransit();
			lock.allowTransit();
			lock.allowTransit();
			lock.transit();
		});
	}

	@Test
	public void testMultiDisallowAllowTransit() {
		var lock = new TransitLock();
		lock.disallowTransit();
		lock.allowTransit();
		lock.disallowTransit();
		lock.disallowTransit();
		lock.allowTransit();
		lock.allowTransit();
		lock.transit();
	}

	@Test
	public void testDisallowTransit() {
		var lock = new TransitLock();
		lock.disallowTransit();
		for (int i = 0; i < 10; i++) {
			Assertions.assertThrows(TimeoutException.class, () -> {
				CompletableFuture.runAsync(lock::transit).get(5, TimeUnit.MILLISECONDS);
			}, "Disallowed transit didn't block a transit");
		}
	}

	@Test
	public void testMultiDisallowTransit() {
		var lock = new TransitLock();
		lock.disallowTransit();
		lock.disallowTransit();
		lock.disallowTransit();
		for (int i = 0; i < 10; i++) {
			Assertions.assertThrows(TimeoutException.class, () -> {
				CompletableFuture.runAsync(lock::transit).get(5, TimeUnit.MILLISECONDS);
			}, "Disallowed transit didn't block a transit");
		}
	}

	@Test
	public void testDeadlocks() {
		var lock = new TransitLock();
		AtomicInteger alreadyRunningTransits = new AtomicInteger();

		var pool = Executors.newFixedThreadPool(500);
		AtomicReference<Exception> failure = new AtomicReference<>();
		for (int i = 0; i < 100; i++) {
			int iF = i;
			pool.submit(() -> {
				try {
					for (int j = 0; j < 500; j++) {
						if (iF % 2 == 0) {
							lock.startTransit();
							alreadyRunningTransits.getAndIncrement();
							alreadyRunningTransits.decrementAndGet();
							lock.endTransit();
						} else {
							lock.disallowTransit();
							Assertions.assertEquals(0, alreadyRunningTransits.get());
							lock.allowTransit();
						}
					}
				} catch (Exception e) {
					e.printStackTrace();
					failure.set(e);
				}
			});
		}
		pool.shutdown();
		if (failure.get() != null) throw new AssertionError(failure.get());
		Assertions.assertDoesNotThrow(() -> pool.awaitTermination(10, TimeUnit.SECONDS));
		Assertions.assertTrue(pool.isTerminated());
	}

	@Test
	public void testParallelTransit() {
		var lock = new TransitLock();
		AtomicInteger alreadyRunningTransits = new AtomicInteger();

		var pool = Executors.newFixedThreadPool(100);
		AtomicReference<AssertionError> failure = new AtomicReference<>();
		for (int i = 0; i < 100; i++) {
			pool.submit(() -> {
				try {
					lock.startTransit();
					alreadyRunningTransits.getAndIncrement();
					try {
						Thread.sleep(20);
					} catch (InterruptedException e) {
						Assertions.fail(e);
					}
					alreadyRunningTransits.decrementAndGet();
					lock.endTransit();
				} catch (AssertionError e) {
					e.printStackTrace();
					failure.set(e);
				}
			});
		}
		lock.disallowTransit();
		Assertions.assertEquals(0, alreadyRunningTransits.get());
		lock.allowTransit();
		pool.shutdown();
		if (failure.get() != null) throw failure.get();
		Assertions.assertDoesNotThrow(() -> pool.awaitTermination(10, TimeUnit.SECONDS));
		Assertions.assertTrue(pool.isTerminated());
	}
}