namespace Nonemm.Recorder.Tests;

public class OpusFileWriterTests : IDisposable
{
    private readonly string path = Path.Combine(Path.GetTempPath(), $"recorder-{Guid.NewGuid():N}.opus");

    public void Dispose() => File.Delete(path);

    private void Write(int channels, int frames, Func<int, int, float> sample)
    {
        using OpusFileWriter writer = new(File.Create(path), channels, 32);
        for (int frame = 0; frame < frames; frame++)
        {
            float[] interleaved = new float[OpusFileWriter.FrameSamples * channels];
            for (int i = 0; i < OpusFileWriter.FrameSamples; i++)
            {
                for (int channel = 0; channel < channels; channel++)
                {
                    interleaved[i * channels + channel] = sample(channel, frame * OpusFileWriter.FrameSamples + i);
                }
            }
            writer.WriteFrame(interleaved);
        }
    }

    private static float Tone(int hertz, int index) =>
        0.5f * (float)Math.Sin(2 * Math.PI * hertz * index / RecorderEngine.SampleRate);

    [Fact]
    public void Each_channel_comes_back_on_its_own_channel()
    {
        Write(3, 10, (channel, index) => channel == 1 ? 0 : Tone(channel == 0 ? 440 : 1000, index));

        OggOpusReader file = OggOpusReader.Read(path);

        Assert.Equal(3, file.Channels);
        Assert.Equal(255, file.MappingFamily);
        Assert.True(OggOpusReader.Rms(file.Pcm[0], 4800, 9600) > 0.25f);
        Assert.True(OggOpusReader.Rms(file.Pcm[1], 4800, 9600) < 0.01f);
        Assert.True(OggOpusReader.Rms(file.Pcm[2], 4800, 9600) > 0.25f);
    }

    [Fact]
    public void The_end_granule_is_the_length_of_the_audio_plus_the_pre_skip()
    {
        Write(2, 10, (_, index) => Tone(440, index));

        OggOpusReader file = OggOpusReader.Read(path);

        Assert.True(file.HasEndMark);
        Assert.Equal(10L * OpusFileWriter.FrameSamples + file.PreSkip, file.FinalGranule);
    }

    [Fact]
    public void One_channel_is_written_as_a_plain_mono_file()
    {
        Write(1, 5, (_, index) => Tone(440, index));

        OggOpusReader file = OggOpusReader.Read(path);

        Assert.Equal(1, file.Channels);
        Assert.Equal(0, file.MappingFamily);
        Assert.True(OggOpusReader.Rms(file.Pcm[0], 4800, 9600) > 0.25f);
    }
}