using AcDream.App.Rendering;

namespace AcDream.App.Tests.Rendering;

public sealed class HostQuiescenceGateTests
{
    [Fact]
    public async Task ExternalStopWaitsForAdmittedCallbackToReturn()
    {
        var gate = new HostQuiescenceGate();
        using var callbackEntered = new ManualResetEventSlim(false);
        using var releaseCallback = new ManualResetEventSlim(false);
        int calls = 0;
        Task callback = Task.Run(() => gate.Invoke(() =>
        {
            callbackEntered.Set();
            Assert.True(releaseCallback.Wait(TimeSpan.FromSeconds(5)));
            calls++;
        }));
        Assert.True(callbackEntered.Wait(TimeSpan.FromSeconds(5)));

        using var stopStarted = new ManualResetEventSlim(false);
        Task stop = Task.Run(() =>
        {
            stopStarted.Set();
            gate.StopAccepting();
        });
        Assert.True(stopStarted.Wait(TimeSpan.FromSeconds(5)));
        await Task.Delay(50);
        Assert.False(stop.IsCompleted);

        releaseCallback.Set();
        await callback;
        await stop;
        gate.Invoke(() => calls++);

        Assert.Equal(1, calls);
        Assert.False(gate.IsAccepting);
    }

    [Fact]
    public void CallbackCanStopGateReentrantlyWithoutDeadlock()
    {
        var gate = new HostQuiescenceGate();
        int calls = 0;

        gate.Invoke(() =>
        {
            calls++;
            gate.StopAccepting();
        });
        gate.Invoke(() => calls++);

        Assert.Equal(1, calls);
        Assert.False(gate.IsAccepting);
    }
}