using System.Text;
using DeepDrftContent.Constants;
using DeepDrftContent.Processors;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using FileDb = DeepDrftContent.FileDatabase.Services.FileDatabase;

namespace DeepDrftTests;

/// <summary>
/// Wave 2 parity tests for the streaming waveform compute. The single most important property: the
/// streaming path (bounded reads, never the whole file in a managed byte[]) must store bytes IDENTICAL
/// to the prior whole-buffer path for the same WAV — for both the 512-bucket profile and the
/// duration-derived high-res datum. These tests compute the profile both ways over the same WAV and
/// assert byte-equality, then cover the bounded-memory guarantee, the mp3/flac graceful-null, and the
/// sample-alignment edges (fewer samples than buckets; a data region whose length is not a whole
/// multiple of the frame size).
/// </summary>
[TestFixture]
public class WaveformStreamingParityTests
{
    private string _testDir = string.Empty;

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

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

    private static WaveformProfileService CreateService(FileDb fileDatabase) =>
        new(
            fileDatabase,
            new AudioProcessor(),
            new RmsLoudnessAlgorithm(),
            Options.Create(new WaveformProfileOptions()),
            NullLogger<WaveformProfileService>.Instance);

    // ----- Parity: 512-bucket profile -----

    [Test]
    public async Task ProfileStreaming_16BitStereo_ByteIdenticalToWholeBuffer()
    {
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        var wav = BuildPcmWav(sampleRate: 44100, channels: 2, bitsPerSample: 16, frames: 50_000);

        var (reference, streaming) = await ComputeProfileBothWaysAsync(service, wav);

        Assert.That(streaming, Is.Not.Null);
        Assert.That(streaming, Is.EqualTo(reference).AsCollection,
            "Streaming 512-bucket profile must be byte-identical to the whole-buffer computation");
    }

    [Test]
    public async Task ProfileStreaming_24BitStereo_NormalizedShape_ByteIdenticalToWholeBuffer()
    {
        // 24-bit standard PCM is exactly what the store path emits when it normalizes a 24-in-32 / float
        // EXTENSIBLE source. bytesPerFrame = 6 exercises odd alignment across the bounded read boundary.
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        var wav = BuildPcmWav(sampleRate: 48000, channels: 2, bitsPerSample: 24, frames: 40_000);

        var (reference, streaming) = await ComputeProfileBothWaysAsync(service, wav);

        Assert.That(streaming, Is.EqualTo(reference).AsCollection,
            "Streaming profile for a 24-bit normalized-shape WAV must be byte-identical");
    }

    // ----- Parity: high-res datum -----

    [Test]
    public async Task HighResStreaming_16BitStereo_ByteIdenticalToWholeBuffer()
    {
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        const double duration = 7.0; // > floor so the bucket count is genuinely duration-derived
        var wav = BuildPcmWav(sampleRate: 44100, channels: 2, bitsPerSample: 16, frames: (int)(44100 * duration));

        await service.ComputeAndStoreHighResAsync(wav, "ref", duration);
        var reference = await service.GetProfileAsync("ref", VaultConstants.TrackWaveforms);

        var stored = await service.ComputeAndStoreHighResStreamingAsync(
            _ => Task.FromResult<Stream?>(new MemoryStream(wav)), "stream", duration);
        var streaming = await service.GetProfileAsync("stream", VaultConstants.TrackWaveforms);

        Assert.That(stored, Is.True);
        Assert.That(streaming, Is.EqualTo(reference).AsCollection,
            "Streaming high-res datum must be byte-identical to the whole-buffer computation");
    }

    [Test]
    public async Task AllStreaming_HotPath_BothDatumsByteIdenticalToWholeBuffer()
    {
        // The upload/replace hot path computes BOTH datums in one streaming pass. Each must match its
        // whole-buffer counterpart exactly.
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        const double duration = 5.0;
        var wav = BuildPcmWav(sampleRate: 44100, channels: 2, bitsPerSample: 16, frames: (int)(44100 * duration));

        await service.ComputeAndStoreAsync(wav, "ref");
        await service.ComputeAndStoreHighResAsync(wav, "ref", duration);
        var refProfile = await service.GetProfileAsync("ref");
        var refHighRes = await service.GetProfileAsync("ref", VaultConstants.TrackWaveforms);

        var stored = await service.ComputeAndStoreAllStreamingAsync(
            _ => Task.FromResult<Stream?>(new MemoryStream(wav)), "stream", duration);
        var streamProfile = await service.GetProfileAsync("stream");
        var streamHighRes = await service.GetProfileAsync("stream", VaultConstants.TrackWaveforms);

        Assert.Multiple(() =>
        {
            Assert.That(stored, Is.True);
            Assert.That(streamProfile, Is.EqualTo(refProfile).AsCollection, "512-bucket profile parity");
            Assert.That(streamHighRes, Is.EqualTo(refHighRes).AsCollection, "high-res datum parity");
        });
    }

    // ----- Bounded memory -----

    [Test]
    public async Task ProfileStreaming_LargeWav_ReadsInBoundedChunks_NeverWholeFile()
    {
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        // ~1.4 MB of PCM — well past any single bounded read, so the consumer is forced to chunk.
        var wav = BuildPcmWav(sampleRate: 44100, channels: 2, bitsPerSample: 16, frames: 180_000);

        var counter = new MaxReadTrackingStream(wav);
        var stored = await service.ComputeAndStoreProfileStreamingAsync(_ => Task.FromResult<Stream?>(counter), "big");

        Assert.Multiple(() =>
        {
            Assert.That(stored, Is.True, "A large, only-chunk-readable WAV must compute successfully");
            Assert.That(counter.MaxSingleRead, Is.LessThanOrEqualTo(81920),
                "No single read may request the whole file — peak buffer is bounded, not O(filesize)");
            Assert.That(counter.ReadCallCount, Is.GreaterThan(1),
                "A file larger than one buffer must be drained across multiple bounded reads");
        });
    }

    // ----- mp3 / flac graceful-null -----

    [Test]
    public async Task ProfileStreaming_NonWavBytes_WritesNoProfile_ReturnsFalse()
    {
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        // Stand-in for mp3/flac: present audio bytes that are not a RIFF/WAVE container.
        var notWav = Encoding.ASCII.GetBytes("ID3 not-a-wav-file-payload-goes-here-and-on-and-on");

        var stored = await service.ComputeAndStoreProfileStreamingAsync(
            _ => Task.FromResult<Stream?>(new MemoryStream(notWav)), "mp3-like");

        Assert.Multiple(() =>
        {
            Assert.That(stored, Is.False, "Non-WAV audio yields no profile (graceful), not a crash");
            Assert.That(service.GetProfileAsync("mp3-like").Result, Is.Null, "No profile must be stored");
        });
    }

    [Test]
    public async Task ProfileStreaming_NoAudioStream_ReturnsNull()
    {
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);

        var stored = await service.ComputeAndStoreProfileStreamingAsync(
            _ => Task.FromResult<Stream?>(null), "missing");

        Assert.That(stored, Is.Null, "No backing audio stream is the tri-state null (maps to 404 upstream)");
    }

    // ----- Sample-alignment edges -----

    [Test]
    public async Task ProfileStreaming_FewerSamplesThanBuckets_ByteIdenticalToWholeBuffer()
    {
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        // 200 frames into 512 buckets — most buckets get zero or one frame; exercises the empty-bucket
        // and single-frame branches identically on both paths.
        var wav = BuildPcmWav(sampleRate: 44100, channels: 2, bitsPerSample: 16, frames: 200);

        var (reference, streaming) = await ComputeProfileBothWaysAsync(service, wav);

        Assert.That(streaming, Is.EqualTo(reference).AsCollection,
            "A WAV with fewer frames than buckets must produce byte-identical output");
    }

    [Test]
    public async Task ProfileStreaming_DataNotWholeMultipleOfFrame_DropsPartialFrameIdentically()
    {
        var db = await FileDb.FromAsync(_testDir);
        var service = CreateService(db!);
        // Declare a data region with a trailing partial frame (blockAlign-1 extra bytes). Both paths must
        // clamp/drop the partial frame the same way, leaving identical output.
        var wav = BuildPcmWav(
            sampleRate: 44100, channels: 2, bitsPerSample: 16, frames: 12_345,
            trailingPartialBytes: 3 /* blockAlign for 16-bit stereo is 4 → a 3-byte partial frame */);

        var (reference, streaming) = await ComputeProfileBothWaysAsync(service, wav);

        Assert.That(streaming, Is.EqualTo(reference).AsCollection,
            "A non-frame-aligned data length must drop the trailing partial frame identically on both paths");
    }

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

    private static async Task<(byte[]? Reference, byte[]? Streaming)> ComputeProfileBothWaysAsync(
        WaveformProfileService service, byte[] wav)
    {
        await service.ComputeAndStoreAsync(wav, "ref");
        var reference = await service.GetProfileAsync("ref");

        var stored = await service.ComputeAndStoreProfileStreamingAsync(
            _ => Task.FromResult<Stream?>(new MemoryStream(wav)), "stream");
        Assert.That(stored, Is.True, "Streaming compute should succeed for a decodable WAV");
        var streaming = await service.GetProfileAsync("stream");

        return (reference, streaming);
    }

    /// <summary>
    /// Builds a standard-PCM WAV with a deterministic broadband (non-silent) data region so the loudness
    /// reduction and peak-normalization are genuinely exercised. <paramref name="trailingPartialBytes"/>
    /// appends bytes that do not complete a frame and includes them in the declared data size, to force
    /// the partial-frame-drop path.
    /// </summary>
    private static byte[] BuildPcmWav(
        int sampleRate, ushort channels, ushort bitsPerSample, int frames, int trailingPartialBytes = 0)
    {
        var blockAlign = (ushort)(channels * (bitsPerSample / 8));
        var byteRate = (uint)(sampleRate * blockAlign);
        var dataLength = frames * blockAlign + trailingPartialBytes;

        var data = new byte[dataLength];
        // Deterministic LCG fill — a broadband signal, identical on every run, non-degenerate per bucket.
        uint state = 0x12345678u;
        for (var i = 0; i < data.Length; i++)
        {
            state = state * 1664525u + 1013904223u;
            data[i] = (byte)(state >> 24);
        }

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

        w.Write(Encoding.ASCII.GetBytes("fmt "));
        w.Write(16u);
        w.Write((ushort)1); // PCM
        w.Write(channels);
        w.Write((uint)sampleRate);
        w.Write(byteRate);
        w.Write(blockAlign);
        w.Write(bitsPerSample);

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

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

    /// <summary>
    /// A seekable read-only stream over a byte buffer that records the largest single read length
    /// requested and how many reads occurred — the assertion mechanism for "the consumer drains in
    /// bounded chunks, never asking for the whole file at once".
    /// </summary>
    private sealed class MaxReadTrackingStream : Stream
    {
        private readonly MemoryStream _inner;

        public MaxReadTrackingStream(byte[] bytes) => _inner = new MemoryStream(bytes, writable: false);

        public int MaxSingleRead { get; private set; }
        public int ReadCallCount { get; private set; }

        private void Track(int count)
        {
            ReadCallCount++;
            if (count > MaxSingleRead) MaxSingleRead = count;
        }

        public override int Read(byte[] buffer, int offset, int count)
        {
            Track(count);
            return _inner.Read(buffer, offset, count);
        }

        public override int Read(Span<byte> buffer)
        {
            Track(buffer.Length);
            return _inner.Read(buffer);
        }

        public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default)
        {
            Track(buffer.Length);
            return _inner.ReadAsync(buffer, cancellationToken);
        }

        public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
        {
            Track(count);
            return _inner.ReadAsync(buffer, offset, count, cancellationToken);
        }

        public override bool CanRead => true;
        public override bool CanSeek => true;
        public override bool CanWrite => false;
        public override long Length => _inner.Length;
        public override long Position { get => _inner.Position; set => _inner.Position = value; }
        public override long Seek(long offset, SeekOrigin origin) => _inner.Seek(offset, origin);
        public override void Flush() { }
        public override void SetLength(long value) => throw new NotSupportedException();
        public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();

        protected override void Dispose(bool disposing)
        {
            if (disposing) _inner.Dispose();
            base.Dispose(disposing);
        }
    }
}