using System;
using Godosa.Core.Audio;
using Xunit;

namespace Godosa.Core.Tests.Audio;

/// <summary>Fixtures: our own sine tones (ffmpeg lavfi sine, amplitude 1/8, 0.25 s) encoded with lame 3.100: mono
/// 440 Hz at 22050 Hz (64 kbit/s, --resample 22.05); stereo 440 Hz left / 880 Hz right at 44100 Hz (128 kbit/s,
/// --resample 44.1). Oracle: a sine of f Hz crosses zero 2·f times a second; counted in a 0.1 s window inside the tone
/// (lame's encoder delay, ≈ 1105 samples, and frame padding are near-silent and cross zero at random).</summary>
public class Mp3Tests
{
    private static readonly byte[] Mono = Convert.FromBase64String("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");
    private static readonly byte[] Stereo = Convert.FromBase64String("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");

    private static (float[] Left, float[] Right) Render(Mp3Stream s, int frames)
    {
        var buf = new float[2 * frames];
        s.Render(buf, frames);
        var (l, r) = (new float[frames], new float[frames]);
        for (var i = 0; i < frames; i++)
            (l[i], r[i]) = (buf[2 * i], buf[2 * i + 1]);
        return (l, r);
    }

    [Fact]
    public void Reader_decodes_mono_at_the_file_rate()
    {
        var clip = Mp3Reader.Read(Mono)!.Value;
        Assert.Equal(22050, clip.SampleRate);
        Assert.InRange(clip.Samples.Length, 5512, 5512 + 3 * 1152);
        var f = Array.ConvertAll(clip.Samples, s => s / 32767f);
        Assert.InRange(SignalStats.ZeroCrossings(f, 2400, 2400 + 2205), 86, 90);   // 0.1 s of 440 Hz → 88
    }

    [Fact]
    public void Reader_downmixes_stereo_to_mono()
    {
        var clip = Mp3Reader.Read(Stereo)!.Value;
        Assert.Equal(44100, clip.SampleRate);
        Assert.InRange(clip.Samples.Length, 11025, 11025 + 3 * 1152);
    }

    [Fact]
    public void Reader_rejects_garbage() => Assert.Null(Mp3Reader.Read(new byte[300]));

    /// <summary>Oracle: both tones are 0.25 s; the LAME tag's encoder delay and padding are not counted (the Info header's
    /// 12 and 11 whole frames would be 0.313 and 0.287 s). Within 1 sample of rounding.</summary>
    [Fact]
    public void Seconds_come_from_the_headers_without_encoder_delay()
    {
        Assert.InRange(Mp3Reader.Seconds(Mono)!.Value, 0.25, 0.25 + 1 / 22050.0);
        Assert.InRange(Mp3Reader.Seconds(Stereo)!.Value, 0.25, 0.25 + 1 / 44100.0);
        Assert.Null(Mp3Reader.Seconds(new byte[300]));
    }

    [Fact]
    public void Stream_keeps_channels_apart()
    {
        using var s = new Mp3Stream(Stereo, loop: false);
        var (l, r) = Render(s, 11025);
        Assert.InRange(SignalStats.ZeroCrossings(l, 4000, 4000 + 4410), 86, 90);     // 440 Hz → 88 in 0.1 s
        Assert.InRange(SignalStats.ZeroCrossings(r, 4000, 4000 + 4410), 174, 178);   // 880 Hz → 176
    }

    [Fact]
    public void Stream_resamples_mono_to_44100_and_duplicates_it()
    {
        using var s = new Mp3Stream(Mono, loop: false);
        var (l, r) = Render(s, 11025);
        Assert.InRange(SignalStats.ZeroCrossings(l, 4000, 4000 + 4410), 86, 90);   // still 440 Hz (176 if played as 44.1 kHz)
        Assert.Equal(l, r);
    }

    [Fact]
    public void Once_only_goes_silent_and_finishes_looping_does_not()
    {
        using var once = new Mp3Stream(Mono, loop: false);
        Render(once, 44100);   // 1 s, past the 0.25 s file
        Assert.True(once.Finished);
        var tail = new float[200];
        Array.Fill(tail, 1f);   // the stream must write the silence, not rely on a cleared buffer
        once.Render(tail, 100);
        Assert.All(tail, x => Assert.Equal(0f, x));
        using var loop = new Mp3Stream(Mono, loop: true);
        var (l, _) = Render(loop, 44100);
        Assert.False(loop.Finished);
        Assert.InRange(SignalStats.Rms(l, 22050), 0.05f, 0.1f);   // second half still sounding (sine 1/8: RMS 0.088 less gaps)
    }
}