using System.Threading;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace AMWD.Common.Tests.Extensions
{
	[TestClass]
	public class ReaderWriterLockSlimExtensionsTests
	{
		[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 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 disposaleWrite = rwLock.GetWriteLock();

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