using DeepDrftContent.Constants;
using DeepDrftContent.FileDatabase.Services;
using DeepDrftContent.FileDatabase.Models;
using DeepDrftContent.Processors;
using DeepDrftModels.Entities;

namespace DeepDrftContent;

/// <summary>
/// Service for managing tracks in both SQL and FileDatabase
/// </summary>
public class TrackContentService
{
    private readonly FileDatabase.Services.FileDatabase _fileDatabase;
    private readonly AudioProcessorRouter _audioProcessorRouter;

    public TrackContentService(FileDatabase.Services.FileDatabase fileDatabase, AudioProcessorRouter audioProcessorRouter)
    {
        _fileDatabase = fileDatabase;
        _audioProcessorRouter = audioProcessorRouter;
    }

    /// <summary>
    /// Adds a new track from a supported audio file (.wav, .mp3, .flac) to both databases. The
    /// router selects the processor by extension; original bytes are stored for mp3/flac (no
    /// transcoding), while EXTENSIBLE WAVs are normalized to standard PCM at storage time.
    /// </summary>
    /// <param name="audioFilePath">Path to the audio file</param>
    /// <param name="trackName">Name of the track</param>
    /// <param name="artist">Artist name</param>
    /// <param name="album">Optional album name</param>
    /// <param name="genre">Optional genre</param>
    /// <param name="releaseDate">Optional release date</param>
    /// <param name="originalFileName">Optional original browser filename captured at upload time</param>
    /// <returns>The track entity with generated ID and media path</returns>
    public async Task<TrackEntity?> AddTrackAsync(
        string audioFilePath,
        string trackName,
        string artist,
        string? album = null,
        string? genre = null,
        DateOnly? releaseDate = null,
        string? originalFileName = null,
        CancellationToken cancellationToken = default)
    {
        try
        {
            // Process the audio file (routed by extension). The returned plan carries metadata plus a
            // streamed writer — no whole-file buffer (the store-path OOM fix).
            var processed = await _audioProcessorRouter.ProcessAudioFileAsync(audioFilePath, cancellationToken);
            if (processed == null)
            {
                throw new InvalidOperationException("Failed to process audio file");
            }

            // Generate a unique track ID
            var trackId = Guid.NewGuid().ToString();

            // Ensure tracks vault exists
            if (!_fileDatabase.HasVault(VaultConstants.Tracks))
            {
                await _fileDatabase.CreateVaultAsync(VaultConstants.Tracks, MediaVaultType.Audio);
            }

            // Stream the audio into the vault. The metadata is supplied directly (there is no in-memory
            // AudioBinary on this path), and the bytes are written progressively from the staging file.
            var metaData = MetaDataFactory.CreateAudioMetaData(trackId, processed.Extension, processed.Duration, processed.Bitrate);
            var success = await _fileDatabase.RegisterResourceStreamingAsync(
                VaultConstants.Tracks, trackId, metaData, processed.WriteToAsync, cancellationToken);
            if (!success)
            {
                throw new InvalidOperationException("Failed to store audio in FileDatabase");
            }

            // Create the track entity for SQL database. Post Phase 8 §8.0 the entity holds only
            // track-cardinal fields; release-cardinal data (artist/album/genre/releaseDate) is
            // resolved into a ReleaseEntity by the caller (UnifiedTrackService) and linked via FK.
            var trackEntity = new TrackEntity
            {
                EntryKey = trackId, // FileDatabase entry ID
                TrackName = trackName,
                OriginalFileName = originalFileName,
                // Persist the processor-extracted runtime to SQL so aggregate queries (total mix runtime)
                // need not touch the vault. Same value the high-res waveform compute reads downstream.
                DurationSeconds = processed.Duration
            };

            return trackEntity;
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            Console.WriteLine($"TrackContentService.AddTrackAsync failed: {ex.Message}");
            return null;
        }
    }

    /// <summary>
    /// Backward-compatible shim — delegates to <see cref="AddTrackAsync"/>. The router accepts WAV
    /// alongside MP3 and FLAC, so this carries no WAV-specific logic of its own.
    /// </summary>
    public Task<TrackEntity?> AddTrackFromWavAsync(
        string wavFilePath,
        string trackName,
        string artist,
        string? album = null,
        string? genre = null,
        DateOnly? releaseDate = null,
        string? originalFileName = null,
        CancellationToken cancellationToken = default) =>
        AddTrackAsync(wavFilePath, trackName, artist, album, genre, releaseDate, originalFileName, cancellationToken);

    /// <summary>
    /// Swaps the audio bytes for an existing track in place: processes a new audio file and
    /// re-registers it under the SAME <paramref name="entryKey"/> in the tracks vault. The track's
    /// vault key — and therefore its SQL link, release membership, position, and metadata — is
    /// untouched; only the binary changes. The new audio is streamed to the vault first; only on
    /// confirmed success is a stale old backing file cleaned up. A cross-format replacement (e.g.
    /// .wav → .flac) leaves the old file on disk under its former filename once the index is updated;
    /// the post-success cleanup removes it. For a same-extension overwrite the register alone suffices.
    /// If the register fails the original audio is left intact and null is returned, so the track
    /// remains playable. Returns the freshly stored audio's <b>duration</b> on success (the caller
    /// re-reads the vault for waveform regen and uses this for the SQL duration write) — matching the
    /// FileDatabase swallow-and-return-null contract. The new bytes are never materialized in memory.
    /// </summary>
    public async Task<double?> ReplaceTrackAudioAsync(string entryKey, string audioFilePath, CancellationToken cancellationToken = default)
    {
        try
        {
            // Capture the old extension from the index metadata (not by loading the file — that would
            // pull the whole old audio into memory). After register the index points to the new
            // extension, so we need the old value now to detect a cross-format swap and clean up the
            // stale file post-success.
            var trackVault = _fileDatabase.GetVault(VaultConstants.Tracks);
            var existingMeta = trackVault is null ? null : await trackVault.GetEntryMetadata(entryKey);
            var oldExtension = existingMeta?.Extension;

            var processed = await _audioProcessorRouter.ProcessAudioFileAsync(audioFilePath, cancellationToken);
            if (processed == null)
            {
                Console.WriteLine($"TrackContentService.ReplaceTrackAudioAsync: processing returned null for {entryKey}");
                return null;
            }

            if (!_fileDatabase.HasVault(VaultConstants.Tracks))
            {
                await _fileDatabase.CreateVaultAsync(VaultConstants.Tracks, MediaVaultType.Audio);
            }

            // Stream the new audio in. This upserts the index entry (new extension recorded) and writes
            // the new file to disk. If this fails the original entry and file are untouched.
            var metaData = MetaDataFactory.CreateAudioMetaData(entryKey, processed.Extension, processed.Duration, processed.Bitrate);
            var success = await _fileDatabase.RegisterResourceStreamingAsync(
                VaultConstants.Tracks, entryKey, metaData, processed.WriteToAsync, cancellationToken);
            if (!success)
            {
                Console.WriteLine($"TrackContentService.ReplaceTrackAudioAsync: vault write failed for {entryKey}; original audio preserved");
                return null;
            }

            // Post-success stale-file cleanup for cross-format swaps. The register wrote the new
            // file (e.g. .flac) and updated the index to the new extension, but the old backing
            // file (e.g. .wav) is now unreferenced on disk. Delete it directly by constructing the
            // old path — RemoveResourceAsync would now resolve to the new extension and delete the
            // wrong file. Non-fatal: an orphaned old file is a disk-hygiene concern, not a
            // playback issue (the index no longer references it).
            if (oldExtension != null && oldExtension != processed.Extension)
            {
                var vault = _fileDatabase.GetVault(VaultConstants.Tracks);
                if (vault != null)
                {
                    var sanitizedKey = System.Text.RegularExpressions.Regex.Replace(entryKey, @"[^a-zA-Z0-9]", "-");
                    var staleFilePath = Path.Combine(vault.RootPath, $"{sanitizedKey}{oldExtension}");
                    try
                    {
                        if (File.Exists(staleFilePath))
                            File.Delete(staleFilePath);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine($"TrackContentService.ReplaceTrackAudioAsync: stale backing-file removal failed for {entryKey} ({staleFilePath}): {ex.Message} — new audio is live; orphaned file may remain on disk");
                    }
                }
            }

            return processed.Duration;
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            Console.WriteLine($"TrackContentService.ReplaceTrackAudioAsync failed: {ex.Message}");
            return null;
        }
    }

    /// <summary>
    /// Retrieves audio binary from FileDatabase
    /// </summary>
    /// <param name="trackId">Track ID (EntryKey)</param>
    /// <returns>Audio binary or null if not found</returns>
    public async Task<AudioBinary?> GetAudioBinaryAsync(string trackId)
    {
        return await _fileDatabase.LoadResourceAsync<AudioBinary>(VaultConstants.Tracks, trackId);
    }

    /// <summary>
    /// Opens a read-only, seekable stream over a track's vault audio, or null if the entry has no
    /// backing file. The caller owns the stream and must dispose it. Unlike <see cref="GetAudioBinaryAsync"/>
    /// this never buffers the whole file — it is the source for the streaming waveform compute. Follows
    /// the FileDatabase swallow-and-return-null contract.
    /// </summary>
    /// <param name="trackId">Track ID (EntryKey)</param>
    public async Task<Stream?> OpenAudioStreamAsync(string trackId)
    {
        var vault = _fileDatabase.GetVault(VaultConstants.Tracks);
        if (vault is null)
        {
            return null;
        }

        var media = await vault.GetEntryStreamAsync(trackId);
        return media?.Stream;
    }

    /// <summary>
    /// Reads a track's stored audio duration from the vault index metadata WITHOUT loading the audio
    /// body — the cheap counterpart of <c>GetAudioBinaryAsync(...).Duration</c>. Returns null if the
    /// entry is unknown or carries no audio metadata. The streaming high-res waveform path uses this to
    /// derive the duration-based bucket count, matching the value the whole-buffer path read off
    /// <see cref="AudioBinary.Duration"/> so the stored datum is byte-identical.
    /// </summary>
    /// <param name="trackId">Track ID (EntryKey)</param>
    public async Task<double?> GetAudioDurationAsync(string trackId)
    {
        var vault = _fileDatabase.GetVault(VaultConstants.Tracks);
        if (vault is null)
        {
            return null;
        }

        var metaData = await vault.GetEntryMetadata(trackId);
        return metaData is AudioMetaData audio ? audio.Duration : null;
    }

    /// <summary>
    /// Checks if FileDatabase is available and tracks vault exists
    /// </summary>
    public bool IsFileDatabaseReady()
    {
        return _fileDatabase.HasVault(VaultConstants.Tracks);
    }

    /// <summary>
    /// Initializes the tracks vault if it doesn't exist
    /// </summary>
    public async Task InitializeTracksVaultAsync()
    {
        if (!_fileDatabase.HasVault(VaultConstants.Tracks))
        {
            await _fileDatabase.CreateVaultAsync(VaultConstants.Tracks, MediaVaultType.Audio);
        }
    }
}