﻿/*
 * Licensed 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
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * 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.
 */

namespace DotPulsar.Tests.Internal
{
    using DotPulsar.Internal;
    using DotPulsar.Internal.Exceptions;
    using FluentAssertions;
    using System.Threading;
    using System.Threading.Tasks;
    using Xunit;

    public class AsyncLockTests
    {
        [Fact]
        public async Task Lock_GivenLockIsFree_ShouldReturnCompletedTask()
        {
            //Arrange
            var sut = new AsyncLock();

            //Act
            var actual = sut.Lock(CancellationToken.None);

            //Assert
            actual.IsCompleted.Should().BeTrue();

            //Annihilate 
            actual.Result.Dispose();
            await sut.DisposeAsync().ConfigureAwait(false);
        }

        [Fact]
        public async Task Lock_GivenLockIsTaken_ShouldReturnIncompletedTask()
        {
            //Arrange
            var sut = new AsyncLock();
            var alreadyTaken = await sut.Lock(CancellationToken.None).ConfigureAwait(false);

            //Act
            var actual = sut.Lock(CancellationToken.None);

            //Assert
            actual.IsCompleted.Should().BeFalse();

            //Annihilate
            alreadyTaken.Dispose();
            actual.Result.Dispose();
            await sut.DisposeAsync().ConfigureAwait(false);
        }

        [Fact]
        public async Task Lock_GivenLockIsDisposed_ShouldThrowAsyncLockDisposedException()
        {
            //Arrange
            var sut = new AsyncLock();
            await sut.DisposeAsync().ConfigureAwait(false);

            //Act
            var exception = await Record.ExceptionAsync(() => sut.Lock(CancellationToken.None)).ConfigureAwait(false);

            //Assert
            exception.Should().BeOfType<AsyncLockDisposedException>();
        }

        [Fact]
        public async Task Lock_GivenLockIsDisposedWhileAwaitingLock_ShouldThrowTaskCanceledException()
        {
            //Arrange
            var sut = new AsyncLock();
            var gotLock = await sut.Lock(CancellationToken.None).ConfigureAwait(false);
            var awaiting = sut.Lock(CancellationToken.None);
            _ = Task.Run(async () => await sut.DisposeAsync().ConfigureAwait(false));

            //Act
            var exception = await Record.ExceptionAsync(() => awaiting).ConfigureAwait(false);

            //Assert
            exception.Should().BeOfType<TaskCanceledException>();

            //Annihilate
            await sut.DisposeAsync().ConfigureAwait(false);
            gotLock.Dispose();
        }

        [Fact]
        public async Task Lock_GivenLockIsTakenAndCancellationTokenIsActivated_ShouldThrowTaskCanceledException()
        {
            //Arrange
            var cts = new CancellationTokenSource();
            var sut = new AsyncLock();
            var gotLock = await sut.Lock(CancellationToken.None).ConfigureAwait(false);
            var awaiting = sut.Lock(cts.Token);

            //Act
            cts.Cancel();
            var exception = await Record.ExceptionAsync(() => awaiting).ConfigureAwait(false);

            //Assert
            exception.Should().BeOfType<TaskCanceledException>();

            //Annihilate
            cts.Dispose();
            gotLock.Dispose();
            await sut.DisposeAsync().ConfigureAwait(false);
        }

        [Fact]
        public async Task Dispose_GivenLockIsDisposedWhileItIsTaken_ShouldNotCompleteBeforeItIsReleased()
        {
            //Arrange
            var sut = new AsyncLock();
            var gotLock = await sut.Lock(CancellationToken.None).ConfigureAwait(false);
            var disposeTask = Task.Run(async () => await sut.DisposeAsync().ConfigureAwait(false));
            Assert.False(disposeTask.IsCompleted);

            //Act
            gotLock.Dispose();
            await disposeTask.ConfigureAwait(false);

            //Assert
            disposeTask.IsCompleted.Should().BeTrue();

            //Annihilate
            await sut.DisposeAsync().ConfigureAwait(false);
        }

        [Fact]
        public async Task Dispose_WhenCalledMultipleTimes_ShouldBeSafeToDoSo()
        {
            //Arrange
            var sut = new AsyncLock();

            //Act
            await sut.DisposeAsync().ConfigureAwait(false);
            var exception = await Record.ExceptionAsync(() => sut.DisposeAsync().AsTask()).ConfigureAwait(false); // xUnit can't record ValueTask yet

            //Assert
            exception.Should().BeNull();
        }
    }
}