using DeepDrftContent.Constants;
using DeepDrftContent.FileDatabase.Models;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using FileDb = DeepDrftContent.FileDatabase.Services.FileDatabase;

namespace DeepDrftContent.Processors;

/// <summary>
/// Computes a track's waveform loudness profile from its WAV bytes and persists it as a sidecar
/// in the <see cref="VaultConstants.WaveformProfiles"/> vault, keyed by the track's EntryKey.
/// The profile is the upload-time, off-the-playback-path representation the frontend fetches to
/// render the WaveformSeeker. The loudness measure is injected (<see cref="ILoudnessAlgorithm"/>)
/// so it can be swapped without changing storage or the wire format.
/// </summary>
public class WaveformProfileService
{
    private const string ProfileExtension = ".wfp";

    /// <summary>Bounded read-buffer size for the streaming PCM pass — the only filesize-independent
    /// allocation on the streaming path (matches the store path's 80 KB copy buffer).</summary>
    private const int StreamReadBufferSize = 81920;

    private readonly FileDb _fileDatabase;
    private readonly AudioProcessor _audioProcessor;
    private readonly ILoudnessAlgorithm _loudnessAlgorithm;
    private readonly WaveformProfileOptions _options;
    private readonly ILogger<WaveformProfileService> _logger;

    public WaveformProfileService(
        FileDb fileDatabase,
        AudioProcessor audioProcessor,
        ILoudnessAlgorithm loudnessAlgorithm,
        IOptions<WaveformProfileOptions> options,
        ILogger<WaveformProfileService> logger)
    {
        _fileDatabase = fileDatabase;
        _audioProcessor = audioProcessor;
        _loudnessAlgorithm = loudnessAlgorithm;
        _options = options.Value;
        _logger = logger;
    }

    /// <summary>
    /// Computes the loudness profile from <paramref name="wavBytes"/> and stores it under
    /// <paramref name="entryKey"/> in <paramref name="vaultName"/> (defaults to
    /// <see cref="VaultConstants.WaveformProfiles"/> when null). Bucket resolution defaults to
    /// <see cref="WaveformProfileOptions.BucketCount"/> (512) when <paramref name="bucketCount"/> is null;
    /// callers pass an explicit count for higher-resolution data — e.g. the per-track high-res datum
    /// derives its count from the audio duration (≈333 samples/sec, see <c>WaveformResolution</c>) so long
    /// tracks are not under-sampled. This service is content-agnostic: it captures however many buckets it is told to and
    /// does not itself decide the count. Returns false (and logs) on any
    /// failure — a missing profile is handled gracefully downstream, so callers on the upload path
    /// log-and-continue rather than failing the upload. Does not throw for expected failure modes.
    /// </summary>
    public async Task<bool> ComputeAndStoreAsync(
        ReadOnlyMemory<byte> wavBytes,
        string entryKey,
        int? bucketCount = null,
        string? vaultName = null)
    {
        var effectiveBucketCount = bucketCount ?? _options.BucketCount;
        var effectiveVaultName = vaultName ?? VaultConstants.WaveformProfiles;

        try
        {
            var pcm = _audioProcessor.TryExtractPcm(wavBytes.Span);
            if (pcm is null)
            {
                _logger.LogWarning(
                    "Waveform profile not computed for {EntryKey}: WAV PCM could not be extracted.",
                    entryKey);
                return false;
            }

            var value = pcm.Value;
            var profile = _loudnessAlgorithm.Compute(
                value.Pcm.Span,
                value.Channels,
                value.SampleRate,
                value.BitsPerSample,
                effectiveBucketCount);

            var quantized = Quantize(profile);

            await EnsureVaultAsync(effectiveVaultName);

            var binary = new MediaBinary(new MediaBinaryParams(quantized, quantized.Length, ProfileExtension));
            var stored = await _fileDatabase.RegisterResourceAsync(effectiveVaultName, entryKey, binary);

            if (!stored)
            {
                _logger.LogWarning("Waveform profile vault write failed for {EntryKey}.", entryKey);
                return false;
            }

            return true;
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            _logger.LogError(ex, "Waveform profile computation failed for {EntryKey}.", entryKey);
            return false;
        }
    }

    /// <summary>
    /// Computes a track's high-resolution loudness datum and stores it in the
    /// <see cref="VaultConstants.TrackWaveforms"/> vault keyed by <paramref name="entryKey"/>. The bucket
    /// count is duration-derived (≈333 samples/sec, clamped — see <see cref="WaveformResolution"/>) so the
    /// datum captures at a constant time resolution regardless of track length. This is the single home
    /// for "the high-res per-track datum" — the upload path, the CMS generate action, and the Mix trigger
    /// all funnel through it, so every track (Mix, Session, Cut) gets an identical datum keyed the same way.
    /// Returns false (logged) on any failure, per the content-agnostic contract above.
    /// </summary>
    public Task<bool> ComputeAndStoreHighResAsync(
        ReadOnlyMemory<byte> wavBytes,
        string entryKey,
        double durationSeconds)
    {
        var bucketCount = WaveformResolution.BucketCountForDuration(durationSeconds);
        return ComputeAndStoreAsync(wavBytes, entryKey, bucketCount, VaultConstants.TrackWaveforms);
    }

    /// <summary>
    /// Streaming counterpart of <see cref="ComputeAndStoreAsync"/>: computes and stores the fixed
    /// 512-bucket player-bar profile by reading the WAV from <paramref name="openWavStream"/> in bounded
    /// chunks, never materializing the whole file in a managed <c>byte[]</c>. Tri-state result matches
    /// the <c>RemoveResourceAsync</c> idiom so callers can map outcomes precisely: <c>null</c> = no audio
    /// stream available (the entry has no backing audio); <c>false</c> = audio present but no profile
    /// computable (non-WAV / float / padded) or the vault write failed; <c>true</c> = stored. Output is
    /// byte-identical to the whole-buffer path for the same WAV.
    /// </summary>
    public Task<bool?> ComputeAndStoreProfileStreamingAsync(
        Func<CancellationToken, Task<Stream?>> openWavStream,
        string entryKey,
        CancellationToken ct = default) =>
        RunStreamingAsync(
            openWavStream, entryKey,
            [(_options.BucketCount, VaultConstants.WaveformProfiles)], ct);

    /// <summary>
    /// Streaming counterpart of <see cref="ComputeAndStoreHighResAsync"/>: computes and stores the
    /// duration-derived high-res datum (<see cref="VaultConstants.TrackWaveforms"/>) by streaming the WAV
    /// from <paramref name="openWavStream"/>. <paramref name="durationSeconds"/> drives the bucket count
    /// exactly as the whole-buffer path's <c>audio.Duration</c> did — pass the same vault-metadata
    /// duration to keep the stored bytes identical. Tri-state result as in
    /// <see cref="ComputeAndStoreProfileStreamingAsync"/>.
    /// </summary>
    public Task<bool?> ComputeAndStoreHighResStreamingAsync(
        Func<CancellationToken, Task<Stream?>> openWavStream,
        string entryKey,
        double durationSeconds,
        CancellationToken ct = default) =>
        RunStreamingAsync(
            openWavStream, entryKey,
            [(WaveformResolution.BucketCountForDuration(durationSeconds), VaultConstants.TrackWaveforms)], ct);

    /// <summary>
    /// Computes and stores BOTH datums a track carries — the 512-bucket profile and the duration-derived
    /// high-res datum — from a SINGLE streaming pass over the WAV. One sequential read of the (possibly
    /// ~GB) audio feeds two independent accumulators, so memory stays O(bucket arrays + read buffer) and
    /// disk I/O is halved versus two separate passes. This is the upload / replace-audio hot path. Each
    /// datum's stored bytes are byte-identical to its whole-buffer counterpart. Tri-state: <c>null</c> =
    /// no audio stream; <c>false</c> = not WAV-decodable or a vault write failed; <c>true</c> = both
    /// datums stored. Best-effort callers ignore the result.
    /// </summary>
    public Task<bool?> ComputeAndStoreAllStreamingAsync(
        Func<CancellationToken, Task<Stream?>> openWavStream,
        string entryKey,
        double durationSeconds,
        CancellationToken ct = default) =>
        RunStreamingAsync(
            openWavStream, entryKey,
            [
                (_options.BucketCount, VaultConstants.WaveformProfiles),
                (WaveformResolution.BucketCountForDuration(durationSeconds), VaultConstants.TrackWaveforms),
            ],
            ct);

    /// <summary>
    /// Core streaming reduction: opens the WAV once, parses its header (bounded), then streams the PCM
    /// data region through one loudness accumulator per requested target, storing each datum. All
    /// targets are computed in the single pass. See the tri-state contract on the public wrappers.
    /// </summary>
    private async Task<bool?> RunStreamingAsync(
        Func<CancellationToken, Task<Stream?>> openWavStream,
        string entryKey,
        IReadOnlyList<(int BucketCount, string VaultName)> targets,
        CancellationToken ct)
    {
        try
        {
            await using var stream = await openWavStream(ct);
            if (stream is null)
            {
                // No backing audio for this entry — distinct from "present but undecodable".
                return null;
            }

            var info = await _audioProcessor.TryReadPcmStreamInfoAsync(stream, stream.Length, ct);
            if (info is null)
            {
                _logger.LogWarning(
                    "Waveform profile not computed for {EntryKey}: WAV PCM could not be extracted (streaming).",
                    entryKey);
                return false;
            }

            var v = info.Value;
            var accumulators = new ILoudnessAccumulator[targets.Count];
            for (var i = 0; i < targets.Count; i++)
            {
                accumulators[i] = _loudnessAlgorithm.CreateAccumulator(
                    v.DataLength, v.Channels, v.SampleRate, v.BitsPerSample, targets[i].BucketCount);
            }

            await StreamPcmThroughAsync(stream, v.DataStart, v.DataLength, accumulators, ct);

            _logger.LogInformation(
                "Streaming waveform compute for {EntryKey}: {DataLength} PCM bytes, {TargetCount} datum(s), " +
                "{BufferSize}B read buffer — no whole-file load.",
                entryKey, v.DataLength, targets.Count, StreamReadBufferSize);

            var allStored = true;
            for (var i = 0; i < targets.Count; i++)
            {
                var profile = accumulators[i].Finish();
                var quantized = Quantize(profile);

                await EnsureVaultAsync(targets[i].VaultName);
                var binary = new MediaBinary(new MediaBinaryParams(quantized, quantized.Length, ProfileExtension));
                var stored = await _fileDatabase.RegisterResourceAsync(targets[i].VaultName, entryKey, binary);
                if (!stored)
                {
                    _logger.LogWarning(
                        "Waveform vault write failed for {EntryKey} in {VaultName}.", entryKey, targets[i].VaultName);
                    allStored = false;
                }
            }

            return allStored;
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            _logger.LogError(ex, "Streaming waveform computation failed for {EntryKey}.", entryKey);
            return false;
        }
    }

    /// <summary>
    /// Seeks to the PCM data region and streams exactly <paramref name="dataLength"/> bytes through each
    /// accumulator in bounded reads. The accumulators carry partial frames internally, so the read
    /// boundaries need not align to frames. Peak memory is one read buffer — independent of file size.
    /// </summary>
    private static async Task StreamPcmThroughAsync(
        Stream stream, long dataStart, long dataLength, ILoudnessAccumulator[] accumulators, CancellationToken ct)
    {
        stream.Seek(dataStart, SeekOrigin.Begin);

        var buffer = new byte[StreamReadBufferSize];
        var remaining = dataLength;
        while (remaining > 0)
        {
            var want = (int)Math.Min(buffer.Length, remaining);
            var read = await stream.ReadAsync(buffer.AsMemory(0, want), ct);
            if (read == 0)
                break;

            var span = buffer.AsSpan(0, read);
            foreach (var accumulator in accumulators)
            {
                accumulator.Add(span);
            }

            remaining -= read;
        }
    }

    /// <summary>
    /// Returns the stored quantized profile bytes for a track from <paramref name="vaultName"/>
    /// (defaults to <see cref="VaultConstants.WaveformProfiles"/> when null), or null if no profile
    /// is stored (existing tracks predate profiling, and computation may have failed). Each byte is
    /// a peak-normalized loudness value in [0, 255].
    /// </summary>
    public async Task<byte[]?> GetProfileAsync(string entryKey, string? vaultName = null)
    {
        var binary = await _fileDatabase.LoadResourceAsync<MediaBinary>(
            vaultName ?? VaultConstants.WaveformProfiles, entryKey);
        return binary?.Buffer;
    }

    /// <summary>
    /// Maps each [0, 1] bucket to a [0, 255] byte. 1.0 maps to 255; the multiply-by-255 with a
    /// truncating cast keeps every in-range value within a byte without a clamp branch.
    /// </summary>
    private static byte[] Quantize(double[] profile)
    {
        var bytes = new byte[profile.Length];
        for (var i = 0; i < profile.Length; i++)
        {
            bytes[i] = (byte)(profile[i] * 255);
        }
        return bytes;
    }

    private async Task EnsureVaultAsync(string vaultName)
    {
        if (!_fileDatabase.HasVault(vaultName))
        {
            await _fileDatabase.CreateVaultAsync(vaultName, MediaVaultType.Media);
        }
    }
}