using System;
using System.Threading;
using System.Threading.Tasks;

namespace AMWD.Common.Tests.Extensions
{
	[TestClass]
	public class ReaderWriterLockSlimExtensionsTest
	{
		[TestMethod]
		public void ShouldEnterReadLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();

			// act
			using var disposable = rwLock.GetReadLock();

			// assert
			Assert.IsNotNull(disposable);
			Assert.IsTrue(rwLock.IsReadLockHeld);
			Assert.IsFalse(rwLock.IsUpgradeableReadLockHeld);
			Assert.IsFalse(rwLock.IsWriteLockHeld);
		}

		[TestMethod]
		public void ShouldEnterUpgradeableReadLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();

			// act
			using var disposable = rwLock.GetUpgradeableReadLock();

			// assert
			Assert.IsNotNull(disposable);
			Assert.IsFalse(rwLock.IsReadLockHeld);
			Assert.IsTrue(rwLock.IsUpgradeableReadLockHeld);
			Assert.IsFalse(rwLock.IsWriteLockHeld);
		}

		[TestMethod]
		public void ShouldAllowWriteLockAfterUpgradableReadLock()
		{
			// arrange
			var rwLockUsing = new ReaderWriterLockSlim();
			var rwLockClassic = new ReaderWriterLockSlim();

			// act
			using var disposableReadUsing = rwLockUsing.GetUpgradeableReadLock();
			using (rwLockUsing.GetWriteLock())
			{
				// assert
				Assert.IsTrue(rwLockUsing.IsUpgradeableReadLockHeld);
				Assert.IsTrue(rwLockUsing.IsWriteLockHeld);
			}
			// assert
			Assert.IsTrue(rwLockUsing.IsUpgradeableReadLockHeld);
			Assert.IsFalse(rwLockUsing.IsWriteLockHeld);

			// act
			using (rwLockClassic.GetUpgradeableReadLock())
			{
				rwLockClassic.EnterWriteLock();

				// assert
				Assert.IsTrue(rwLockClassic.IsUpgradeableReadLockHeld);
				Assert.IsTrue(rwLockClassic.IsWriteLockHeld);
			}
			// assert
			Assert.IsFalse(rwLockClassic.IsUpgradeableReadLockHeld);
			Assert.IsFalse(rwLockClassic.IsWriteLockHeld);
		}

		[TestMethod]
		public void ShouldEnterWriteLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();

			// act
			using var disposable = rwLock.GetWriteLock();

			// assert
			Assert.IsNotNull(disposable);
			Assert.IsFalse(rwLock.IsReadLockHeld);
			Assert.IsFalse(rwLock.IsUpgradeableReadLockHeld);
			Assert.IsTrue(rwLock.IsWriteLockHeld);
		}

		[TestMethod]
		public void ShouldNotAllowWriteLockAfterReadLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();

			// act
			using var disposableRead = rwLock.GetReadLock();
			try
			{
				using var disposaleWrite = rwLock.GetWriteLock();
				Assert.Fail();
			}
			catch (LockRecursionException)
			{ }

			// assert
			Assert.IsNotNull(disposableRead);
			Assert.IsTrue(rwLock.IsReadLockHeld);
			Assert.IsFalse(rwLock.IsUpgradeableReadLockHeld);
			Assert.IsFalse(rwLock.IsWriteLockHeld);
		}

		[TestMethod]
		public void ShouldAllowWriteLockAfterUpgradeableReadLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();

			// act
			using var disposableRead = rwLock.GetUpgradeableReadLock();
			using var disposableWrite = rwLock.GetWriteLock();

			// assert
			Assert.IsNotNull(disposableRead);
			Assert.IsNotNull(disposableWrite);
			Assert.IsFalse(rwLock.IsReadLockHeld);
			Assert.IsTrue(rwLock.IsUpgradeableReadLockHeld);
			Assert.IsTrue(rwLock.IsWriteLockHeld);
		}

		[TestMethod]
		public void ShouldGetTimeoutOnReadLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();
			bool isTimeout = false;

			// act
			using var disposableRead = rwLock.GetWriteLock();
			var awaitableTask = Task.Run(() =>
			{
				try
				{
					using var disposableRead = rwLock.GetReadLock(10);
					Assert.Fail();
				}
				catch (TimeoutException)
				{
					isTimeout = true;
				}
				catch (Exception)
				{ /* keep it quiet */ }
			});
			awaitableTask.Wait();

			// assert
			Assert.IsTrue(isTimeout);
		}

		[TestMethod]
		public void ShouldGetTimeoutOnUpgradeableReadLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();
			bool isTimeout = false;

			// act
			using var disposableRead = rwLock.GetWriteLock();
			var awaitableTask = Task.Run(() =>
			{
				try
				{
					using var disposableRead = rwLock.GetUpgradeableReadLock(10);
					Assert.Fail();
				}
				catch (TimeoutException)
				{
					isTimeout = true;
				}
				catch (Exception)
				{ /* keep it quiet */ }
			});
			awaitableTask.Wait();

			// assert
			Assert.IsTrue(isTimeout);
		}

		[TestMethod]
		public void ShouldGetTimeoutOnWriteLock()
		{
			// arrange
			var rwLock = new ReaderWriterLockSlim();
			bool isTimeout = false;

			// act
			using var disposableRead = rwLock.GetReadLock();
			var awaitableTask = Task.Run(() =>
			{
				try
				{
					using var disposableRead = rwLock.GetWriteLock(10);
					Assert.Fail();
				}
				catch (TimeoutException)
				{
					isTimeout = true;
				}
				catch (Exception)
				{ /* keep it quiet */ }
			});
			awaitableTask.Wait();

			// assert
			Assert.IsTrue(isTimeout);
		}
	}
}