using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;

[MemoryDiagnoser]
public class Program
{
    static void Main(string[] args) => BenchmarkSwitcher.FromAssemblies(new[] { typeof(Program).Assembly }).Run(args);

    private static readonly Task s_incompleteTask = new TaskCompletionSource<bool>().Task;
    private static readonly CancellationToken s_uncanceledToken = new CancellationTokenSource().Token;
    private static readonly SemaphoreSlim s_sem = new SemaphoreSlim(0);

    private const int Iterations = 1_000;

    [Benchmark(OperationsPerInvoke = Iterations)]
    public async Task SemaphoreWait()
    {
        for (int i = 0; i < Iterations; i++)
        {
            Task t = s_sem.WaitAsync(s_uncanceledToken);
            s_sem.Release();
            await t;
        }
    }

    [Benchmark(OperationsPerInvoke = Iterations)]
    public async Task WhenAny_Incomplete()
    {
        for (int i = 0; i < Iterations; i++)
        {
            AsyncTaskMethodBuilder atmb = default;
            Task t = Task.WhenAny(atmb.Task, s_incompleteTask);
            atmb.SetResult();
            await t;
        }
    }

    [Benchmark(OperationsPerInvoke = Iterations)]
    public async Task WhenAny_Complete()
    {
        for (int i = 0; i < Iterations; i++)
        {
            await Task.WhenAny(Task.CompletedTask, s_incompleteTask);
        }
    }
}