using System.Collections.Immutable;
using Bugsnag;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Errors;
using ErsatzTV.Core.Extensions;
using ErsatzTV.Core.Interfaces.FFmpeg;
using ErsatzTV.Core.Interfaces.Images;
using ErsatzTV.Core.Interfaces.Metadata;
using ErsatzTV.Core.Interfaces.Repositories;
using ErsatzTV.Core.MediaSources;
using ErsatzTV.Core.Metadata;
using ErsatzTV.Scanner.Core.Interfaces.FFmpeg;
using ErsatzTV.Scanner.Core.Interfaces.Metadata;
using Microsoft.Extensions.Logging;

namespace ErsatzTV.Scanner.Core.Metadata;

public class TelevisionFolderScanner : LocalFolderScanner, ITelevisionFolderScanner
{
    private readonly IClient _client;
    private readonly IFallbackMetadataProvider _fallbackMetadataProvider;
    private readonly ILibraryRepository _libraryRepository;
    private readonly ILocalFileSystem _localFileSystem;
    private readonly ILocalMetadataProvider _localMetadataProvider;
    private readonly ILocalSubtitlesProvider _localSubtitlesProvider;
    private readonly ILogger<TelevisionFolderScanner> _logger;
    private readonly IMediaItemRepository _mediaItemRepository;
    private readonly IMediator _mediator;
    private readonly IMetadataRepository _metadataRepository;
    private readonly ITelevisionRepository _televisionRepository;

    public TelevisionFolderScanner(
        ILocalFileSystem localFileSystem,
        ITelevisionRepository televisionRepository,
        ILocalStatisticsProvider localStatisticsProvider,
        ILocalMetadataProvider localMetadataProvider,
        ILocalSubtitlesProvider localSubtitlesProvider,
        IMetadataRepository metadataRepository,
        IImageCache imageCache,
        ILibraryRepository libraryRepository,
        IMediaItemRepository mediaItemRepository,
        IMediator mediator,
        IFFmpegPngService ffmpegPngService,
        ITempFilePool tempFilePool,
        IClient client,
        IFallbackMetadataProvider fallbackMetadataProvider,
        ILogger<TelevisionFolderScanner> logger) : base(
        localFileSystem,
        localStatisticsProvider,
        metadataRepository,
        mediaItemRepository,
        imageCache,
        ffmpegPngService,
        tempFilePool,
        client,
        logger)
    {
        _localFileSystem = localFileSystem;
        _televisionRepository = televisionRepository;
        _localMetadataProvider = localMetadataProvider;
        _localSubtitlesProvider = localSubtitlesProvider;
        _metadataRepository = metadataRepository;
        _libraryRepository = libraryRepository;
        _mediaItemRepository = mediaItemRepository;
        _mediator = mediator;
        _client = client;
        _fallbackMetadataProvider = fallbackMetadataProvider;
        _logger = logger;
    }

    public async Task<Either<BaseError, Unit>> ScanFolder(
        LibraryPath libraryPath,
        string ffmpegPath,
        string ffprobePath,
        decimal progressMin,
        decimal progressMax,
        CancellationToken cancellationToken)
    {
        try
        {
            decimal progressSpread = progressMax - progressMin;

            string normalizedLibraryPath = libraryPath.Path.TrimEnd(
                Path.DirectorySeparatorChar,
                Path.AltDirectorySeparatorChar);
            if (libraryPath.Path != normalizedLibraryPath)
            {
                await _libraryRepository.UpdatePath(libraryPath, normalizedLibraryPath);
            }

            ImmutableHashSet<string> allTrashedItems = await _mediaItemRepository.GetAllTrashedItems(libraryPath);

            var allShowFolders = _localFileSystem.ListSubdirectories(libraryPath.Path)
                .Filter(ShouldIncludeFolder)
                .OrderBy(identity)
                .ToList();

            foreach (string showFolder in allShowFolders)
            {
                if (cancellationToken.IsCancellationRequested)
                {
                    return new ScanCanceled();
                }

                decimal percentCompletion = (decimal)allShowFolders.IndexOf(showFolder) / allShowFolders.Count;
                await _mediator.Publish(
                    new ScannerProgressUpdate(
                        libraryPath.LibraryId,
                        null,
                        progressMin + percentCompletion * progressSpread,
                        Array.Empty<int>(),
                        Array.Empty<int>()),
                    cancellationToken);

                Option<int> maybeParentFolder = await _libraryRepository.GetParentFolderId(showFolder);

                // this folder is unused by the show, but will be used as parents of season folders
                LibraryFolder _ = await _libraryRepository.GetOrAddFolder(
                    libraryPath,
                    maybeParentFolder,
                    showFolder);

                Either<BaseError, MediaItemScanResult<Show>> maybeShow =
                    await FindOrCreateShow(libraryPath.Id, showFolder)
                        .BindT(show => UpdateMetadataForShow(show, showFolder))
                        .BindT(show => UpdateArtworkForShow(show, showFolder, ArtworkKind.Poster, cancellationToken))
                        .BindT(show => UpdateArtworkForShow(show, showFolder, ArtworkKind.FanArt, cancellationToken))
                        .BindT(
                            show => UpdateArtworkForShow(show, showFolder, ArtworkKind.Thumbnail, cancellationToken));

                foreach (BaseError error in maybeShow.LeftToSeq())
                {
                    _logger.LogWarning(
                        "Error processing show in folder {Folder}: {Error}",
                        showFolder,
                        error.Value);
                }

                foreach (MediaItemScanResult<Show> result in maybeShow.RightToSeq())
                {
                    // add show to search index right away
                    if (result.IsAdded || result.IsUpdated)
                    {
                        await _mediator.Publish(
                            new ScannerProgressUpdate(
                                libraryPath.LibraryId,
                                null,
                                null,
                                new[] { result.Item.Id },
                                Array.Empty<int>()),
                            cancellationToken);
                    }

                    Either<BaseError, Unit> scanResult = await ScanSeasons(
                        libraryPath,
                        ffmpegPath,
                        ffprobePath,
                        result.Item,
                        showFolder,
                        allTrashedItems,
                        cancellationToken);

                    foreach (ScanCanceled error in scanResult.LeftToSeq().OfType<ScanCanceled>())
                    {
                        return error;
                    }
                }
            }

            foreach (string path in await _televisionRepository.FindEpisodePaths(libraryPath))
            {
                if (!_localFileSystem.FileExists(path))
                {
                    _logger.LogInformation("Flagging missing episode at {Path}", path);

                    List<int> episodeIds = await FlagFileNotFound(libraryPath, path);
                    await _mediator.Publish(
                        new ScannerProgressUpdate(
                            libraryPath.LibraryId,
                            null,
                            null,
                            episodeIds.ToArray(),
                            Array.Empty<int>()),
                        cancellationToken);
                }
                else if (Path.GetFileName(path).StartsWith("._", StringComparison.OrdinalIgnoreCase))
                {
                    _logger.LogInformation("Removing dot underscore file at {Path}", path);
                    await _televisionRepository.DeleteByPath(libraryPath, path);
                }
            }

            await _libraryRepository.CleanEtagsForLibraryPath(libraryPath);

            await _televisionRepository.DeleteEmptySeasons(libraryPath);
            List<int> ids = await _televisionRepository.DeleteEmptyShows(libraryPath);
            await _mediator.Publish(
                new ScannerProgressUpdate(
                    libraryPath.LibraryId,
                    null,
                    null,
                    Array.Empty<int>(),
                    ids.ToArray()),
                cancellationToken);

            return Unit.Default;
        }
        catch (Exception ex) when (ex is TaskCanceledException or OperationCanceledException)
        {
            return new ScanCanceled();
        }
    }

    private async Task<Either<BaseError, MediaItemScanResult<Show>>> FindOrCreateShow(
        int libraryPathId,
        string showFolder)
    {
        ShowMetadata metadata = await _localMetadataProvider.GetMetadataForShow(showFolder);
        Option<Show> maybeShow = await _televisionRepository.GetShowByMetadata(libraryPathId, metadata, showFolder);

        foreach (Show show in maybeShow)
        {
            return new MediaItemScanResult<Show>(show);
        }

        return await _televisionRepository.AddShow(libraryPathId, metadata);
    }

    private async Task<Either<BaseError, Unit>> ScanSeasons(
        LibraryPath libraryPath,
        string ffmpegPath,
        string ffprobePath,
        Show show,
        string showFolder,
        ImmutableHashSet<string> allTrashedItems,
        CancellationToken cancellationToken)
    {
        foreach (string seasonFolder in _localFileSystem.ListSubdirectories(showFolder).Filter(ShouldIncludeFolder)
                     .OrderBy(identity))
        {
            if (cancellationToken.IsCancellationRequested)
            {
                return new ScanCanceled();
            }

            Option<int> maybeParentFolder = await _libraryRepository.GetParentFolderId(seasonFolder);

            string etag = FolderEtag.CalculateWithSubfolders(seasonFolder, _localFileSystem);
            LibraryFolder knownFolder = await _libraryRepository.GetOrAddFolder(
                libraryPath,
                maybeParentFolder,
                seasonFolder);

            // skip folder if etag matches
            if (knownFolder.Etag == etag)
            {
                if (allTrashedItems.Any(f => f.StartsWith(seasonFolder, StringComparison.OrdinalIgnoreCase)))
                {
                    _logger.LogDebug("Previously trashed items are now present in folder {Folder}", seasonFolder);
                }
                else
                {
                    // etag matches and no trashed items are now present, continue to next folder
                    continue;
                }
            }

            Option<int> maybeSeasonNumber = _fallbackMetadataProvider.GetSeasonNumberForFolder(seasonFolder);
            foreach (int seasonNumber in maybeSeasonNumber)
            {
                Either<BaseError, Season> maybeSeason = await _televisionRepository
                    .GetOrAddSeason(show, libraryPath.Id, seasonNumber)
                    .BindT(EnsureMetadataExists)
                    .BindT(season => UpdatePoster(season, seasonFolder, cancellationToken));

                foreach (BaseError error in maybeSeason.LeftToSeq())
                {
                    _logger.LogWarning(
                        "Error processing season in folder {Folder}: {Error}",
                        seasonFolder,
                        error.Value);
                }

                foreach (Season season in maybeSeason.RightToSeq())
                {
                    Either<BaseError, Unit> scanResult = await ScanEpisodes(
                        libraryPath,
                        knownFolder,
                        ffmpegPath,
                        ffprobePath,
                        season,
                        seasonFolder,
                        cancellationToken);

                    foreach (ScanCanceled error in scanResult.LeftToSeq().OfType<ScanCanceled>())
                    {
                        return error;
                    }

                    await _libraryRepository.SetEtag(libraryPath, knownFolder, seasonFolder, etag);

                    season.Show = show;

                    await _mediator.Publish(
                        new ScannerProgressUpdate(
                            libraryPath.LibraryId,
                            null,
                            null,
                            new[] { season.Id },
                            Array.Empty<int>()),
                        cancellationToken);
                }
            }
        }

        return Unit.Default;
    }

    private async Task<Either<BaseError, Unit>> ScanEpisodes(
        LibraryPath libraryPath,
        LibraryFolder seasonFolder,
        string ffmpegPath,
        string ffprobePath,
        Season season,
        string seasonPath,
        CancellationToken cancellationToken)
    {
        var allSeasonFiles = _localFileSystem.ListSubdirectories(seasonPath)
            .Map(_localFileSystem.ListFiles)
            .Flatten()
            .Append(_localFileSystem.ListFiles(seasonPath))
            .Filter(f => VideoFileExtensions.Contains(Path.GetExtension(f)))
            .Filter(f => !Path.GetFileName(f).StartsWith("._", StringComparison.OrdinalIgnoreCase))
            .OrderBy(identity)
            .ToList();

        foreach (string file in allSeasonFiles)
        {
            // TODO: figure out how to rebuild playlists
            Either<BaseError, Episode> maybeEpisode = await _televisionRepository
                .GetOrAddEpisode(season, libraryPath, seasonFolder, file)
                .BindT(
                    episode => UpdateStatistics(new MediaItemScanResult<Episode>(episode), ffmpegPath, ffprobePath)
                        .MapT(_ => episode))
                .BindT(video => UpdateLibraryFolderId(video, seasonFolder))
                .BindT(UpdateMetadata)
                .BindT(e => UpdateThumbnail(e, cancellationToken))
                .BindT(UpdateSubtitles)
                .BindT(e => FlagNormal(new MediaItemScanResult<Episode>(e)))
                .MapT(r => r.Item);

            foreach (BaseError error in maybeEpisode.LeftToSeq())
            {
                _logger.LogWarning("Error processing episode at {Path}: {Error}", file, error.Value);
            }

            foreach (Episode episode in maybeEpisode.RightToSeq())
            {
                await _mediator.Publish(
                    new ScannerProgressUpdate(
                        libraryPath.LibraryId,
                        null,
                        null,
                        new[] { episode.Id },
                        Array.Empty<int>()),
                    cancellationToken);
            }
        }

        // TODO: remove missing episodes?

        return Unit.Default;
    }

    private async Task<Either<BaseError, MediaItemScanResult<Show>>> UpdateMetadataForShow(
        MediaItemScanResult<Show> result,
        string showFolder)
    {
        try
        {
            Show show = result.Item;

            Option<string> maybeNfo = LocateNfoFileForShow(showFolder);
            if (maybeNfo.IsNone)
            {
                if (!Optional(show.ShowMetadata).Flatten().Any())
                {
                    _logger.LogDebug("Refreshing {Attribute} for {Path}", "Fallback Metadata", showFolder);
                    if (await _localMetadataProvider.RefreshFallbackMetadata(show, showFolder))
                    {
                        result.IsUpdated = true;
                    }
                }
            }

            foreach (string nfoFile in maybeNfo)
            {
                bool shouldUpdate = Optional(show.ShowMetadata).Flatten().HeadOrNone().Match(
                    m => m.MetadataKind == MetadataKind.Fallback ||
                         m.DateUpdated != _localFileSystem.GetLastWriteTime(nfoFile),
                    true);

                if (shouldUpdate)
                {
                    _logger.LogDebug("Refreshing {Attribute} from {Path}", "Sidecar Metadata", nfoFile);
                    if (await _localMetadataProvider.RefreshSidecarMetadata(show, nfoFile))
                    {
                        result.IsUpdated = true;
                    }
                }
            }

            return result;
        }
        catch (Exception ex)
        {
            _client.Notify(ex);
            return BaseError.New(ex.ToString());
        }
    }

    private async Task<Either<BaseError, Season>> EnsureMetadataExists(Season season)
    {
        season.SeasonMetadata ??= new List<SeasonMetadata>();

        if (season.SeasonMetadata.Count == 0)
        {
            var metadata = new SeasonMetadata
            {
                SeasonId = season.Id,
                Season = season,
                DateAdded = DateTime.UtcNow,
                Guids = new List<MetadataGuid>(),
                Tags = new List<Tag>()
            };

            season.SeasonMetadata.Add(metadata);
            await _metadataRepository.Add(metadata);
        }

        return season;
    }

    private async Task<Either<BaseError, Episode>> UpdateLibraryFolderId(Episode episode, LibraryFolder libraryFolder)
    {
        MediaFile mediaFile = episode.GetHeadVersion().MediaFiles.Head();
        if (mediaFile.LibraryFolderId != libraryFolder.Id)
        {
            await _libraryRepository.UpdateLibraryFolderId(mediaFile, libraryFolder.Id);
        }

        return episode;
    }

    private async Task<Either<BaseError, Episode>> UpdateMetadata(Episode episode)
    {
        try
        {
            Option<string> maybeNfo = LocateNfoFile(episode);
            if (maybeNfo.IsNone)
            {
                bool shouldUpdate = Optional(episode.EpisodeMetadata).Flatten().HeadOrNone().Match(
                    m => m.DateUpdated == SystemTime.MinValueUtc,
                    true);

                if (shouldUpdate)
                {
                    string path = episode.MediaVersions.Head().MediaFiles.Head().Path;
                    _logger.LogDebug("Refreshing {Attribute} for {Path}", "Fallback Metadata", path);
                    await _localMetadataProvider.RefreshFallbackMetadata(episode);
                }
            }

            foreach (string nfoFile in maybeNfo)
            {
                bool shouldUpdate = Optional(episode.EpisodeMetadata).Flatten().HeadOrNone().Match(
                    m => m.MetadataKind == MetadataKind.Fallback ||
                         m.DateUpdated != _localFileSystem.GetLastWriteTime(nfoFile),
                    true);

                if (shouldUpdate)
                {
                    _logger.LogDebug("Refreshing {Attribute} from {Path}", "Sidecar Metadata", nfoFile);
                    await _localMetadataProvider.RefreshSidecarMetadata(episode, nfoFile);
                }
            }

            return episode;
        }
        catch (Exception ex)
        {
            _client.Notify(ex);
            return BaseError.New(ex.ToString());
        }
    }

    private async Task<Either<BaseError, MediaItemScanResult<Show>>> UpdateArtworkForShow(
        MediaItemScanResult<Show> result,
        string showFolder,
        ArtworkKind artworkKind,
        CancellationToken cancellationToken)
    {
        try
        {
            Show show = result.Item;
            Option<string> maybeArtwork = LocateArtworkForShow(showFolder, artworkKind);
            foreach (string artworkFile in maybeArtwork)
            {
                ShowMetadata metadata = show.ShowMetadata.Head();
                await RefreshArtwork(artworkFile, metadata, artworkKind, None, None, cancellationToken);
            }

            return result;
        }
        catch (Exception ex)
        {
            _client.Notify(ex);
            return BaseError.New(ex.ToString());
        }
    }

    private async Task<Either<BaseError, Season>> UpdatePoster(
        Season season,
        string seasonFolder,
        CancellationToken cancellationToken)
    {
        try
        {
            Option<string> maybePoster = LocatePoster(season, seasonFolder);
            foreach (string posterFile in maybePoster)
            {
                SeasonMetadata metadata = season.SeasonMetadata.Head();
                await RefreshArtwork(posterFile, metadata, ArtworkKind.Poster, None, None, cancellationToken);
            }

            return season;
        }
        catch (Exception ex)
        {
            _client.Notify(ex);
            return BaseError.New(ex.ToString());
        }
    }

    private async Task<Either<BaseError, Episode>> UpdateThumbnail(Episode episode, CancellationToken cancellationToken)
    {
        try
        {
            Option<string> maybeThumbnail = LocateThumbnail(episode);
            foreach (string thumbnailFile in maybeThumbnail)
            {
                foreach (EpisodeMetadata metadata in episode.EpisodeMetadata)
                {
                    await RefreshArtwork(
                        thumbnailFile,
                        metadata,
                        ArtworkKind.Thumbnail,
                        None,
                        None,
                        cancellationToken);
                }
            }

            return episode;
        }
        catch (Exception ex)
        {
            _client.Notify(ex);
            return BaseError.New(ex.ToString());
        }
    }

    private async Task<Either<BaseError, Episode>> UpdateSubtitles(Episode episode)
    {
        try
        {
            await _localSubtitlesProvider.UpdateSubtitles(episode, None, true);
            return episode;
        }
        catch (Exception ex)
        {
            _client.Notify(ex);
            return BaseError.New(ex.ToString());
        }
    }

    private Option<string> LocateNfoFileForShow(string showFolder) =>
        Optional(Path.Combine(showFolder, "tvshow.nfo")).Filter(s => _localFileSystem.FileExists(s));

    private Option<string> LocateNfoFile(Episode episode)
    {
        string path = episode.MediaVersions.Head().MediaFiles.Head().Path;
        return Optional(Path.ChangeExtension(path, "nfo")).Filter(s => _localFileSystem.FileExists(s));
    }

    private Option<string> LocateArtworkForShow(string showFolder, ArtworkKind artworkKind)
    {
        string[] segments = artworkKind switch
        {
            ArtworkKind.Poster => new[] { "poster", "folder" },
            ArtworkKind.FanArt => new[] { "fanart" },
            ArtworkKind.Thumbnail => new[] { "thumb" },
            _ => throw new ArgumentOutOfRangeException(nameof(artworkKind))
        };

        return ImageFileExtensions
            .Map(ext => segments.Map(segment => $"{segment}.{ext}"))
            .Flatten()
            .Map(f => Path.Combine(showFolder, f))
            .Filter(s => _localFileSystem.FileExists(s))
            .HeadOrNone();
    }

    private Option<string> LocatePoster(Season season, string seasonFolder)
    {
        string folder = Path.GetDirectoryName(seasonFolder) ?? string.Empty;
        return ImageFileExtensions
            .Map(ext => Path.Combine(folder, $"season{season.SeasonNumber:00}-poster.{ext}"))
            .Filter(s => _localFileSystem.FileExists(s))
            .HeadOrNone();
    }

    private Option<string> LocateThumbnail(Episode episode)
    {
        string path = episode.MediaVersions.Head().MediaFiles.Head().Path;
        string folder = Path.GetDirectoryName(path) ?? string.Empty;
        return ImageFileExtensions
            .Map(ext => Path.GetFileNameWithoutExtension(path) + $"-thumb.{ext}")
            .Map(f => Path.Combine(folder, f))
            .Filter(f => _localFileSystem.FileExists(f))
            .HeadOrNone();
    }
}