using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using MQTTnet.Internal;

namespace MQTTnet.Tests
{
    [TestClass]
    public class AsyncLock_Tests
    {
        [TestMethod]
        public async Task Lock_Serial_Calls()
        {
            var sum = 0;

            var @lock = new AsyncLock();
            for (var i = 0; i < 100; i++)
            {
                using (await @lock.WaitAsync(CancellationToken.None).ConfigureAwait(false))
                {
                    sum++;
                }
            }

            Assert.AreEqual(100, sum);
        }

        [TestMethod]
        [ExpectedException(typeof(TaskCanceledException))]
        public async Task Test_Cancellation()
        {
            var @lock = new AsyncLock();

            // This call will never "release" the lock due to missing _using_.
            await @lock.WaitAsync(CancellationToken.None).ConfigureAwait(false);

            using (var cts = new CancellationTokenSource(TimeSpan.FromSeconds(3)))
            {
                await @lock.WaitAsync(cts.Token).ConfigureAwait(false);
            }
        }

        //[TestMethod]
        //public async Task Test_Cancellation_With_Later_Access()
        //{
        //    var @lock = new AsyncLock();

        //    var releaser = await @lock.WaitAsync().ConfigureAwait(false);

        //    try
        //    {
        //        using (var cts = new CancellationTokenSource(TimeSpan.FromSeconds(3)))
        //        {
        //            await @lock.WaitAsync(cts.Token).ConfigureAwait(false);
        //        }
        //    }
        //    catch (OperationCanceledException)
        //    {
        //    }
            
        //    releaser.Dispose();

        //    using (await @lock.WaitAsync().ConfigureAwait(false))
        //    {
        //        // When the method finished, the thread got access.
        //    }
        //}

        [TestMethod]
        public void Lock_10_Parallel_Tasks()
        {
            const int ThreadsCount = 10;

            var threads = new Task[ThreadsCount];
            var @lock = new AsyncLock();
            var globalI = 0;
            for (var i = 0; i < ThreadsCount; i++)
            {
#pragma warning disable CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
                threads[i] = Task.Run(async () =>
                {
                    using (var releaser = await @lock.WaitAsync(CancellationToken.None))
                    {
                        var localI = globalI;
                        await Task.Delay(10); // Increase the chance for wrong data.
                        localI++;
                        globalI = localI;
                    }
                });
#pragma warning restore CS4014 // Because this call is not awaited, execution of the current method continues before the call is completed
            }

            Task.WaitAll(threads);
            Assert.AreEqual(ThreadsCount, globalI);
        }
    }
}