deepdrft/DeepDrftTests/AudioProcessorTests.cs

using System.Text;
using DeepDrftContent.Processors;

namespace DeepDrftTests;

/// <summary>
/// Tests for <see cref="AudioProcessor.ProcessWavFileAsync"/> WAV format handling — standard PCM,
/// EXTENSIBLE-PCM, EXTENSIBLE IEEE float, padded 24-in-32, and the default-fallback paths.
/// </summary>
[TestFixture]
public class AudioProcessorTests
{
    private const ushort WaveFormatPcm = 0x0001;
    private const ushort WaveFormatExtensible = 0xFFFE;

    private string _testDir = string.Empty;

    [SetUp]
    public void SetUp()
    {
        _testDir = Path.Combine(Path.GetTempPath(), "AudioProcessorTests", Guid.NewGuid().ToString());
        Directory.CreateDirectory(_testDir);
    }

    [TearDown]
    public void TearDown()
    {
        try { Directory.Delete(_testDir, recursive: true); }
        catch { /* Best-effort cleanup — ignore failures */ }
    }

    [Test]
    public async Task StandardPcm_RoundTripsUnchanged()
    {
        var path = await WriteWavAsync(BuildMinimalWav(channels: 2, sampleRate: 44100, bitsPerSample: 16, audioFormat: WaveFormatPcm));

        var audio = await new AudioProcessor().ProcessWavFileAsync(path);

        Assert.That(audio, Is.Not.Null);
        Assert.That(audio!.Duration, Is.GreaterThan(0.0));
        Assert.That(audio.Bitrate, Is.GreaterThan(0));
    }

    [Test]
    public async Task ExtensiblePcm_NormalizesToStandardHeader()
    {
        var subFormat = SubFormatGuid(WaveFormatPcm);
        var wav = BuildMinimalWav(channels: 2, sampleRate: 44100, bitsPerSample: 16, audioFormat: WaveFormatExtensible,
            subFormatGuid: subFormat, validBitsPerSample: 16);
        var path = await WriteWavAsync(wav);

        var audio = await new AudioProcessor().ProcessWavFileAsync(path);

        Assert.That(audio, Is.Not.Null);
        Assert.That(audio!.Duration, Is.GreaterThan(0.0));
        Assert.That(audio.Bitrate, Is.GreaterThan(0));
        Assert.That(ReadFmtAudioFormat(audio.Buffer), Is.EqualTo(WaveFormatPcm), "Stored buffer must be standard PCM");
    }

    [Test]
    public async Task ExtensibleIeeeFloat_AcceptedAndConverted()
    {
        // Two stereo frames of 32-bit float samples (range [-1.0, 1.0]).
        var samples = FloatBytes(0.5f, -0.5f, 1.0f, -1.0f);
        var subFormat = SubFormatGuid(0x0003); // WAVE_FORMAT_IEEE_FLOAT
        var wav = BuildMinimalWav(channels: 2, sampleRate: 44100, bitsPerSample: 32, audioFormat: WaveFormatExtensible,
            sampleData: samples, subFormatGuid: subFormat, validBitsPerSample: 32);
        var path = await WriteWavAsync(wav);

        var audio = await new AudioProcessor().ProcessWavFileAsync(path);

        Assert.That(audio, Is.Not.Null);
        Assert.That(ReadFmtBitsPerSample(audio!.Buffer), Is.EqualTo(16 + 8), "Float must convert to 24-bit PCM");
        Assert.That(ReadFmtAudioFormat(audio.Buffer), Is.EqualTo(WaveFormatPcm));
        // 4 float samples (4 bytes each) → 4 PCM samples (3 bytes each) = 12 data bytes after the 44-byte header.
        Assert.That(audio.Buffer.Length, Is.EqualTo(44 + 12));
    }

    [Test]
    public async Task ExtensiblePadded24in32_AcceptedAndRepacked()
    {
        // Two stereo frames; each sample is a 24-bit value stored in a 32-bit little-endian container.
        var samples = Padded24In32Bytes(0x123456, unchecked((int)0xFFEDCBA9), 0x000001, unchecked((int)0xFF800000));
        var subFormat = SubFormatGuid(WaveFormatPcm);
        var wav = BuildMinimalWav(channels: 2, sampleRate: 44100, bitsPerSample: 32, audioFormat: WaveFormatExtensible,
            sampleData: samples, subFormatGuid: subFormat, validBitsPerSample: 24);
        var path = await WriteWavAsync(wav);

        var audio = await new AudioProcessor().ProcessWavFileAsync(path);

        Assert.That(audio, Is.Not.Null);
        Assert.That(ReadFmtBitsPerSample(audio!.Buffer), Is.EqualTo(24), "Padded container must repack to 24-bit");
        Assert.That(ReadFmtAudioFormat(audio.Buffer), Is.EqualTo(WaveFormatPcm));
        // 4 container samples (4 bytes each) → 4 PCM samples (3 bytes each) = 12 data bytes.
        Assert.That(audio.Buffer.Length, Is.EqualTo(44 + 12));
    }

    [Test]
    public async Task ExtensibleUnsupportedSubFormat_FallsBackToDefaults()
    {
        var subFormat = SubFormatGuid(0x0005); // WAVE_FORMAT_DOLBY_AC3 — neither PCM nor float
        var wav = BuildMinimalWav(channels: 2, sampleRate: 44100, bitsPerSample: 16, audioFormat: WaveFormatExtensible,
            subFormatGuid: subFormat, validBitsPerSample: 16);
        var path = await WriteWavAsync(wav);

        var audio = await new AudioProcessor().ProcessWavFileAsync(path);

        Assert.That(audio, Is.Not.Null);
        Assert.That(audio!.Duration, Is.EqualTo(180.0), "Unsupported SubFormat must fall back to default metadata");
    }

    [Test]
    public async Task ExtensibleFmtTooSmall_FallsBackToDefaults()
    {
        // audioFormat=EXTENSIBLE but fmt chunk declares 16 bytes — too small for the extension.
        var wav = BuildMinimalWav(channels: 2, sampleRate: 44100, bitsPerSample: 16, audioFormat: WaveFormatExtensible,
            forceFmtChunkSize: 16);
        var path = await WriteWavAsync(wav);

        var audio = await new AudioProcessor().ProcessWavFileAsync(path);

        Assert.That(audio, Is.Not.Null);
        Assert.That(audio!.Duration, Is.EqualTo(180.0), "Undersized EXTENSIBLE fmt chunk must fall back to default metadata");
    }

    // -- helpers --------------------------------------------------------------------------------

    /// <summary>
    /// Synthesises a minimal valid WAV buffer. For EXTENSIBLE (audioFormat=0xFFFE) the fmt chunk is
    /// 40 bytes and includes cbSize, wValidBitsPerSample, channel mask, and the SubFormat GUID. For
    /// standard PCM (audioFormat=1) the fmt chunk is 16 bytes. When <paramref name="sampleData"/> is
    /// null a small block of silence sized to the block alignment is used.
    /// </summary>
    private static byte[] BuildMinimalWav(
        int channels,
        int sampleRate,
        int bitsPerSample,
        ushort audioFormat,
        byte[]? sampleData = null,
        byte[]? subFormatGuid = null,
        ushort validBitsPerSample = 0,
        uint? forceFmtChunkSize = null)
    {
        var isExtensible = audioFormat == WaveFormatExtensible;
        var fmtChunkSize = forceFmtChunkSize ?? (isExtensible ? 40u : 16u);

        var blockAlign = (ushort)(channels * (bitsPerSample / 8));
        var byteRate = (uint)(sampleRate * blockAlign);
        var data = sampleData ?? new byte[blockAlign * 2];

        using var ms = new MemoryStream();
        using var w = new BinaryWriter(ms, Encoding.ASCII, leaveOpen: true);

        w.Write(Encoding.ASCII.GetBytes("RIFF"));
        w.Write((uint)(36 + fmtChunkSize - 16 + data.Length)); // riff size adjusted for fmt extension
        w.Write(Encoding.ASCII.GetBytes("WAVE"));

        w.Write(Encoding.ASCII.GetBytes("fmt "));
        w.Write(fmtChunkSize);
        w.Write(audioFormat);
        w.Write((ushort)channels);
        w.Write((uint)sampleRate);
        w.Write(byteRate);
        w.Write(blockAlign);
        w.Write((ushort)bitsPerSample);

        // Only emit the EXTENSIBLE extension when the declared fmt size actually allows for it. A
        // forced-small size (fmt=16) leaves audioFormat=EXTENSIBLE but no extension, exercising the
        // "fmt too small" fallback.
        if (fmtChunkSize >= 40)
        {
            w.Write((ushort)22); // cbSize
            w.Write(validBitsPerSample);
            w.Write((uint)0); // channel mask
            w.Write(subFormatGuid ?? SubFormatGuid(WaveFormatPcm));
        }

        w.Write(Encoding.ASCII.GetBytes("data"));
        w.Write((uint)data.Length);
        w.Write(data);

        w.Flush();
        return ms.ToArray();
    }

    /// <summary>Builds a 16-byte SubFormat GUID whose leading 2 bytes are the format tag.</summary>
    private static byte[] SubFormatGuid(ushort formatTag)
    {
        var guid = new byte[16];
        guid[0] = (byte)(formatTag & 0xFF);
        guid[1] = (byte)((formatTag >> 8) & 0xFF);
        // Remaining 14 bytes are the fixed KSDATAFORMAT suffix; their value is irrelevant to parsing.
        return guid;
    }

    private static byte[] FloatBytes(params float[] samples)
    {
        var bytes = new byte[samples.Length * 4];
        for (int i = 0; i < samples.Length; i++)
        {
            BitConverter.GetBytes(samples[i]).CopyTo(bytes, i * 4);
        }
        return bytes;
    }

    /// <summary>Packs each 24-bit sample value into a 32-bit little-endian container.</summary>
    private static byte[] Padded24In32Bytes(params int[] samples)
    {
        var bytes = new byte[samples.Length * 4];
        for (int i = 0; i < samples.Length; i++)
        {
            BitConverter.GetBytes(samples[i]).CopyTo(bytes, i * 4);
        }
        return bytes;
    }

    private async Task<string> WriteWavAsync(byte[] wav)
    {
        var path = Path.Combine(_testDir, Guid.NewGuid() + ".wav");
        await File.WriteAllBytesAsync(path, wav);
        return path;
    }

    private static ushort ReadFmtAudioFormat(byte[] standardPcmWav) => BitConverter.ToUInt16(standardPcmWav, 20);

    private static ushort ReadFmtBitsPerSample(byte[] standardPcmWav) => BitConverter.ToUInt16(standardPcmWav, 34);
}