meeting-assistant/MeetingAssistant.Tests/MicrophoneAudioSourceTests.cs

using MeetingAssistant.Recording;
using Microsoft.Extensions.Logging.Abstractions;

namespace MeetingAssistant.Tests;

public sealed class MicrophoneAudioSourceTests
{
    [Fact]
    public async Task CaptureMovesToNewlyResolvedMicrophoneWhenCurrentCaptureFails()
    {
        var captureSources = new SequenceMicrophoneCaptureSourceFactory(
            new FailingAfterChunkAudioSource(Pcm16(1_000)),
            new ActiveAudioSource(Pcm16(2_000)));
        var source = new MicrophoneAudioSource(
            captureSources,
            NullLogger<MicrophoneAudioSource>.Instance,
            TimeSpan.Zero);
        using var cancellation = new CancellationTokenSource(TimeSpan.FromSeconds(5));
        await using var chunks = source
            .CaptureAsync(new MeetingAssistantOptions(), cancellation.Token)
            .GetAsyncEnumerator(cancellation.Token);

        Assert.True(await chunks.MoveNextAsync());
        Assert.Equal(1_000, BitConverter.ToInt16(chunks.Current.Pcm));
        Assert.True(await chunks.MoveNextAsync());
        Assert.Equal(2_000, BitConverter.ToInt16(chunks.Current.Pcm));
        Assert.Equal(2, captureSources.CaptureCreationCount);

        await cancellation.CancelAsync();
    }

    [Fact]
    public async Task CaptureWaitsForMicrophoneToBecomeAvailable()
    {
        var captureSources = new InitiallyUnavailableMicrophoneCaptureSourceFactory(
            new ActiveAudioSource(Pcm16(3_000)));
        var source = new MicrophoneAudioSource(
            captureSources,
            NullLogger<MicrophoneAudioSource>.Instance,
            TimeSpan.Zero);
        using var cancellation = new CancellationTokenSource(TimeSpan.FromSeconds(5));
        await using var chunks = source
            .CaptureAsync(new MeetingAssistantOptions(), cancellation.Token)
            .GetAsyncEnumerator(cancellation.Token);

        Assert.True(await chunks.MoveNextAsync());
        Assert.Equal(3_000, BitConverter.ToInt16(chunks.Current.Pcm));
        Assert.Equal(2, captureSources.CaptureCreationCount);

        await cancellation.CancelAsync();
    }

    [Fact]
    public async Task AcceptedNewMicrophoneReplacesCaptureWithinTheSameStream()
    {
        var selection = new MicrophoneDeviceSelection();
        var devices = new SelectableCaptureDevices(selection);
        var prompts = new AcceptingPrompt();
        var monitor = new MicrophoneSwitchMonitor(devices, prompts,
            NullLogger<MicrophoneSwitchMonitor>.Instance, TimeSpan.FromMilliseconds(10), TimeSpan.FromMinutes(1));
        var source = new MicrophoneAudioSource(devices, NullLogger<MicrophoneAudioSource>.Instance,
            TimeSpan.Zero, monitor, selection);
        using var lifetime = new CancellationTokenSource(TimeSpan.FromSeconds(5));
        await using var chunks = source.CaptureAsync(new MeetingAssistantOptions(), lifetime.Token).GetAsyncEnumerator();
        try
        {
            Assert.True(await chunks.MoveNextAsync());
            Assert.Equal(1_000, BitConverter.ToInt16(chunks.Current.Pcm));
            devices.Available = [new("old", "Built-in"), new("new", "USB headset")];
            Assert.Equal("new", (await prompts.Shown.Task.WaitAsync(TimeSpan.FromSeconds(2))).Id);
            var nextChunk = chunks.MoveNextAsync().AsTask();
            Assert.False(nextChunk.IsCompleted);
            Assert.Null(selection.SelectedDeviceId);

            prompts.Response.SetResult(true);

            Assert.True(await nextChunk.WaitAsync(TimeSpan.FromSeconds(2)));
            Assert.Equal(2_000, BitConverter.ToInt16(chunks.Current.Pcm));
            Assert.Equal("new", selection.SelectedDeviceId);
            Assert.False(lifetime.IsCancellationRequested);
        }
        finally
        {
            await lifetime.CancelAsync();
        }
    }

    [Fact]
    public async Task EndingMeetingDuringCreationDisposesAbandonedCapture()
    {
        using var lifetime = new CancellationTokenSource(TimeSpan.FromSeconds(5));
        var abandonedCapture = new DisposableAudioSource();
        var factory = new CallbackCaptureFactory(() =>
        {
            lifetime.Cancel();
            return abandonedCapture;
        });
        var source = new MicrophoneAudioSource(factory, NullLogger<MicrophoneAudioSource>.Instance);
        await using var chunks = source.CaptureAsync(lifetime.Token).GetAsyncEnumerator();

        Assert.False(await chunks.MoveNextAsync());
        Assert.True(abandonedCapture.Disposed);
    }

    private sealed class CallbackCaptureFactory(Func<IMeetingAudioSource> create) : IMicrophoneCaptureSourceFactory
    {
        public IMeetingAudioSource CreateCapture(MeetingAssistantOptions options) => create();
    }

    [Fact]
    public async Task AcceptedSwitchDuringCreationDisposesAbandonedCapture()
    {
        var selection = new MicrophoneDeviceSelection();
        var devices = new SwitchDuringCreationDevices(selection);
        var prompts = new AcceptingPrompt();
        prompts.Response.SetResult(true);
        var monitor = new MicrophoneSwitchMonitor(devices, prompts,
            NullLogger<MicrophoneSwitchMonitor>.Instance, TimeSpan.FromMilliseconds(10), TimeSpan.FromMinutes(1));
        var source = new MicrophoneAudioSource(devices, NullLogger<MicrophoneAudioSource>.Instance,
            TimeSpan.Zero, monitor, selection);
        using var lifetime = new CancellationTokenSource(TimeSpan.FromSeconds(5));
        await using var chunks = source.CaptureAsync(new MeetingAssistantOptions(), lifetime.Token).GetAsyncEnumerator();
        try
        {
            Assert.True(await chunks.MoveNextAsync());
            Assert.Equal("new", selection.SelectedDeviceId);
            Assert.Equal(2_000, BitConverter.ToInt16(chunks.Current.Pcm));
            Assert.True(devices.AbandonedCapture.Disposed);
        }
        finally
        {
            await lifetime.CancelAsync();
        }
    }

    private sealed class SwitchDuringCreationDevices(MicrophoneDeviceSelection selection)
        : IMicrophoneDeviceProvider, IMicrophoneCaptureSourceFactory
    {
        private MicrophoneDevice[] available = [new("old", "Built-in")];
        private int creations;
        private volatile bool switchObserved;
        public DisposableAudioSource AbandonedCapture { get; } = new();
        public IReadOnlyList<MicrophoneDevice> GetAvailableMicrophones()
        {
            if (selection.SelectedDeviceId == "new") switchObserved = true;
            return Volatile.Read(ref available);
        }
        public MicrophoneDeviceSnapshot GetMicrophoneSnapshot(MeetingAssistantOptions options)
            => new(GetAvailableMicrophones(), available[0]);

        public IMeetingAudioSource CreateCapture(MeetingAssistantOptions options)
        {
            if (++creations > 1) return new ActiveAudioSource(Pcm16(2_000));
            Volatile.Write(ref available, [new("old", "Built-in"), new("new", "USB headset")]);
            // Let the acceptance callback finish before returning the already-opened source.
            if (!SpinWait.SpinUntil(() => switchObserved, TimeSpan.FromSeconds(2)))
                throw new TimeoutException("The new microphone was not selected during capture creation.");
            return AbandonedCapture;
        }
    }

    private sealed class DisposableAudioSource : IMeetingAudioSource, IDisposable
    {
        public bool Disposed { get; private set; }
        public IAsyncEnumerable<AudioChunk> CaptureAsync(CancellationToken cancellationToken)
            => new ActiveAudioSource(Pcm16(1_000)).CaptureAsync(cancellationToken);
        public void Dispose() => Disposed = true;
    }

    private sealed class AcceptingPrompt : IMicrophoneSwitchPromptService
    {
        public TaskCompletionSource<MicrophoneDevice> Shown { get; } = new(TaskCreationOptions.RunContinuationsAsynchronously);
        public TaskCompletionSource<bool> Response { get; } = new(TaskCreationOptions.RunContinuationsAsynchronously);
        public Task<bool> ConfirmSwitchAsync(MicrophoneDevice microphone, CancellationToken cancellationToken)
        {
            Shown.TrySetResult(microphone);
            return Response.Task.WaitAsync(cancellationToken);
        }
    }

    private sealed class SelectableCaptureDevices(MicrophoneDeviceSelection selection)
        : IMicrophoneDeviceProvider, IMicrophoneCaptureSourceFactory
    {
        public volatile MicrophoneDevice[] Available = [new("old", "Built-in")];
        public IReadOnlyList<MicrophoneDevice> GetAvailableMicrophones() => Available;
        public MicrophoneDeviceSnapshot GetMicrophoneSnapshot(MeetingAssistantOptions options)
            => new(Available, selection.Resolve(options.Recording.MicrophoneDeviceId, Available[0], Available));
        public IMeetingAudioSource CreateCapture(MeetingAssistantOptions options)
            => new ActiveAudioSource(Pcm16(GetMicrophoneSnapshot(options).Current!.Id == "new" ? (short)2_000 : (short)1_000));
    }

    private static byte[] Pcm16(short sample)
    {
        return BitConverter.GetBytes(sample);
    }

    private sealed class SequenceMicrophoneCaptureSourceFactory(params IMeetingAudioSource[] sources)
        : IMicrophoneCaptureSourceFactory
    {
        private readonly Queue<IMeetingAudioSource> sources = new(sources);

        public int CaptureCreationCount { get; private set; }

        public IMeetingAudioSource CreateCapture(MeetingAssistantOptions options)
        {
            CaptureCreationCount++;
            return sources.Dequeue();
        }
    }

    private sealed class InitiallyUnavailableMicrophoneCaptureSourceFactory(IMeetingAudioSource availableSource)
        : IMicrophoneCaptureSourceFactory
    {
        public int CaptureCreationCount { get; private set; }

        public IMeetingAudioSource CreateCapture(MeetingAssistantOptions options)
        {
            CaptureCreationCount++;
            if (CaptureCreationCount == 1)
            {
                throw new InvalidOperationException("No microphone is currently available.");
            }

            return availableSource;
        }
    }

    private sealed class FailingAfterChunkAudioSource(byte[] pcm) : IMeetingAudioSource
    {
        public async IAsyncEnumerable<AudioChunk> CaptureAsync(
            [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
        {
            await Task.Yield();
            yield return new AudioChunk(pcm, 16000, 1);
            throw new InvalidOperationException("The active microphone was disconnected.");
        }
    }

    private sealed class ActiveAudioSource(byte[] pcm) : IMeetingAudioSource
    {
        public async IAsyncEnumerable<AudioChunk> CaptureAsync(
            [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken)
        {
            yield return new AudioChunk(pcm, 16000, 1);
            await Task.Delay(Timeout.InfiniteTimeSpan, cancellationToken);
        }
    }
}