namespace Nonemm.Recorder.Tests;

public class RecorderEngineTests : IDisposable
{
    private readonly string path = Path.Combine(Path.GetTempPath(), $"recorder-{Guid.NewGuid():N}.opus");
    private readonly FakeBackend backend = new();
    private readonly RecorderEngine engine;

    public RecorderEngineTests()
    {
        engine = new RecorderEngine(backend);
    }

    public void Dispose()
    {
        engine.Dispose();
        File.Delete(path);
    }

    [Fact]
    public void A_channel_of_a_missing_device_stays_in_the_list_as_unavailable()
    {
        RecorderChannel channel = engine.AddChannel(new ChannelSource("Gone", false, 0, 1));

        Assert.False(channel.IsAvailable);
        Assert.Single(engine.Channels);
        Assert.Equal("not connected", channel.Problem);
    }

    [Fact]
    public void A_device_that_appears_is_opened_and_its_channel_becomes_available()
    {
        RecorderChannel channel = engine.AddChannel(new ChannelSource("Mic", false, 0, 1));

        backend.Devices.Add(new AudioDeviceInfo("Mic", false, 1));
        engine.Refresh();

        Assert.True(channel.IsAvailable);
        Assert.True(backend.IsOpen("Mic"));
    }

    [Fact]
    public void A_device_that_is_unplugged_is_closed_and_its_channel_is_kept()
    {
        backend.Devices.Add(new AudioDeviceInfo("Mic", false, 1));
        RecorderChannel channel = engine.AddChannel(new ChannelSource("Mic", false, 0, 1));

        backend.Devices.Clear();
        engine.Refresh();

        Assert.False(channel.IsAvailable);
        Assert.False(backend.IsOpen("Mic"));
        Assert.Single(engine.Channels);
    }

    [Fact]
    public void A_channel_past_the_end_of_the_device_is_unavailable()
    {
        backend.Devices.Add(new AudioDeviceInfo("Line In", false, 2));

        RecorderChannel channel = engine.AddChannel(new ChannelSource("Line In", false, 5, 8));

        Assert.False(channel.IsAvailable);
    }

    [Fact]
    public void The_two_sides_of_a_stereo_device_are_two_channels()
    {
        backend.Devices.Add(new AudioDeviceInfo("Line In", false, 2));
        RecorderChannel left = engine.AddChannel(new ChannelSource("Line In", false, 0, 2));
        RecorderChannel right = engine.AddChannel(new ChannelSource("Line In", false, 1, 2));

        backend.Push("Line In", 2, 480, channel: 1, value: 0.5f);

        Assert.Equal(0f, left.TakePeak());
        Assert.Equal(0.5f, right.TakePeak());
    }

    [Fact]
    public void An_unavailable_channel_is_recorded_as_silence_and_picks_up_when_it_appears()
    {
        backend.Devices.Add(new AudioDeviceInfo("Mic", false, 1));
        engine.AddChannel(new ChannelSource("Mic", false, 0, 1));
        engine.AddChannel(new ChannelSource("Radio", false, 0, 1));

        engine.StartRecording(path, 32);
        Feed(seconds: 1, "Mic");
        backend.Devices.Add(new AudioDeviceInfo("Radio", false, 1));
        engine.Refresh();
        Feed(seconds: 1, "Mic", "Radio");
        engine.StopRecording();

        OggOpusReader file = OggOpusReader.Read(path);
        Assert.Equal(2, file.Channels);
        int second = RecorderEngine.SampleRate;
        Assert.True(OggOpusReader.Rms(file.Pcm[0], second / 4, second / 2) > 0.2f);
        Assert.True(OggOpusReader.Rms(file.Pcm[1], second / 4, second / 2) < 0.01f);
        Assert.True(OggOpusReader.Rms(file.Pcm[1], second + second / 4, second / 2) > 0.2f);
    }

    [Fact]
    public void The_channels_cannot_change_during_a_recording()
    {
        backend.Devices.Add(new AudioDeviceInfo("Mic", false, 1));
        engine.AddChannel(new ChannelSource("Mic", false, 0, 1));
        engine.StartRecording(path, 32);

        Assert.Throws<InvalidOperationException>(() => engine.AddChannel(new ChannelSource("Mic", false, 0, 1)));
    }

    [Fact]
    public void Monitoring_opens_the_playback_device_once_and_closes_it_with_the_last_channel()
    {
        backend.Devices.Add(new AudioDeviceInfo("Mic", false, 1));
        RecorderChannel first = engine.AddChannel(new ChannelSource("Mic", false, 0, 1));
        RecorderChannel second = engine.AddChannel(new ChannelSource("Mic", false, 0, 1));

        engine.SetMonitored(first, true);
        engine.SetMonitored(second, true);
        engine.SetMonitored(first, false);

        Assert.Equal(1, backend.PlaybackOpened);
        engine.SetMonitored(second, false);
        engine.SetMonitored(first, true);
        Assert.Equal(2, backend.PlaybackOpened);
    }

    // a tone in real time, 10 ms at a time, as a device delivers it
    private void Feed(int seconds, params string[] names)
    {
        for (int step = 0; step < seconds * 100; step++)
        {
            foreach (string name in names)
            {
                backend.Push(name, 1, 480, channel: 0, value: step % 2 == 0 ? 0.4f : -0.4f);
            }
            Thread.Sleep(10);
        }
    }
}