using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Interfaces.Emby;
using ErsatzTV.Core.Interfaces.Metadata;
using ErsatzTV.Core.Interfaces.Repositories;
using ErsatzTV.Core.Interfaces.Search;
using ErsatzTV.Core.Metadata;
using LanguageExt;
using LanguageExt.UnsafeValueAccess;
using MediatR;
using Microsoft.Extensions.Logging;
using Unit = LanguageExt.Unit;

namespace ErsatzTV.Core.Emby
{
    public class EmbyMovieLibraryScanner : IEmbyMovieLibraryScanner
    {
        private readonly IEmbyApiClient _embyApiClient;
        private readonly ILocalFileSystem _localFileSystem;
        private readonly ILocalStatisticsProvider _localStatisticsProvider;
        private readonly ILogger<EmbyMovieLibraryScanner> _logger;
        private readonly IMediaSourceRepository _mediaSourceRepository;
        private readonly IMediator _mediator;
        private readonly IMovieRepository _movieRepository;
        private readonly IEmbyPathReplacementService _pathReplacementService;
        private readonly ISearchIndex _searchIndex;
        private readonly ISearchRepository _searchRepository;

        public EmbyMovieLibraryScanner(
            IEmbyApiClient embyApiClient,
            ISearchIndex searchIndex,
            IMediator mediator,
            IMovieRepository movieRepository,
            ISearchRepository searchRepository,
            IEmbyPathReplacementService pathReplacementService,
            IMediaSourceRepository mediaSourceRepository,
            ILocalFileSystem localFileSystem,
            ILocalStatisticsProvider localStatisticsProvider,
            ILogger<EmbyMovieLibraryScanner> logger)
        {
            _embyApiClient = embyApiClient;
            _searchIndex = searchIndex;
            _mediator = mediator;
            _movieRepository = movieRepository;
            _searchRepository = searchRepository;
            _pathReplacementService = pathReplacementService;
            _mediaSourceRepository = mediaSourceRepository;
            _localFileSystem = localFileSystem;
            _localStatisticsProvider = localStatisticsProvider;
            _logger = logger;
        }

        public async Task<Either<BaseError, Unit>> ScanLibrary(
            string address,
            string apiKey,
            EmbyLibrary library,
            string ffprobePath)
        {
            List<EmbyItemEtag> existingMovies = await _movieRepository.GetExistingEmbyMovies(library);

            // TODO: maybe get quick list of item ids and etags from api to compare first
            // TODO: paging?

            List<EmbyPathReplacement> pathReplacements = await _mediaSourceRepository
                .GetEmbyPathReplacements(library.MediaSourceId);

            Either<BaseError, List<EmbyMovie>> maybeMovies = await _embyApiClient.GetMovieLibraryItems(
                address,
                apiKey,
                library.MediaSourceId,
                library.ItemId);

            await maybeMovies.Match(
                async movies =>
                {
                    var validMovies = new List<EmbyMovie>();
                    foreach (EmbyMovie movie in movies.OrderBy(m => m.MovieMetadata.Head().Title))
                    {
                        string localPath = _pathReplacementService.GetReplacementEmbyPath(
                            pathReplacements,
                            movie.MediaVersions.Head().MediaFiles.Head().Path,
                            false);

                        if (!_localFileSystem.FileExists(localPath))
                        {
                            _logger.LogWarning("Skipping emby movie that does not exist at {Path}", localPath);
                        }
                        else
                        {
                            validMovies.Add(movie);
                        }
                    }

                    foreach (EmbyMovie incoming in validMovies)
                    {
                        decimal percentCompletion = (decimal) validMovies.IndexOf(incoming) / validMovies.Count;
                        await _mediator.Publish(new LibraryScanProgress(library.Id, percentCompletion));

                        Option<EmbyItemEtag> maybeExisting =
                            existingMovies.Find(ie => ie.ItemId == incoming.ItemId);

                        var updateStatistics = false;

                        await maybeExisting.Match(
                            async existing =>
                            {
                                try
                                {
                                    if (existing.Etag == incoming.Etag)
                                    {
                                        // _logger.LogDebug(
                                        //     $"NOOP: Etag has not changed for movie {incoming.MovieMetadata.Head().Title}");
                                        return;
                                    }

                                    _logger.LogDebug(
                                        "UPDATE: Etag has changed for movie {Movie}",
                                        incoming.MovieMetadata.Head().Title);

                                    updateStatistics = true;
                                    incoming.LibraryPathId = library.Paths.Head().Id;
                                    Option<EmbyMovie> updated = await _movieRepository.UpdateEmby(incoming);
                                    if (updated.IsSome)
                                    {
                                        await _searchIndex.UpdateItems(
                                            _searchRepository,
                                            new List<MediaItem> { updated.ValueUnsafe() });
                                    }
                                }
                                catch (Exception ex)
                                {
                                    updateStatistics = false;
                                    _logger.LogError(
                                        ex,
                                        "Error updating movie {Movie}",
                                        incoming.MovieMetadata.Head().Title);
                                }
                            },
                            async () =>
                            {
                                try
                                {
                                    // _logger.LogDebug(
                                    //     $"INSERT: Item id is new for movie {incoming.MovieMetadata.Head().Title}");

                                    updateStatistics = true;
                                    incoming.LibraryPathId = library.Paths.Head().Id;
                                    if (await _movieRepository.AddEmby(incoming))
                                    {
                                        await _searchIndex.AddItems(
                                            _searchRepository,
                                            new List<MediaItem> { incoming });
                                    }
                                }
                                catch (Exception ex)
                                {
                                    updateStatistics = false;
                                    _logger.LogError(
                                        ex,
                                        "Error adding movie {Movie}",
                                        incoming.MovieMetadata.Head().Title);
                                }
                            });

                        if (updateStatistics)
                        {
                            string localPath = _pathReplacementService.GetReplacementEmbyPath(
                                pathReplacements,
                                incoming.MediaVersions.Head().MediaFiles.Head().Path,
                                false);

                            _logger.LogDebug("Refreshing {Attribute} for {Path}", "Statistics", localPath);
                            Either<BaseError, bool> refreshResult =
                                await _localStatisticsProvider.RefreshStatistics(ffprobePath, incoming, localPath);

                            await refreshResult.Match(
                                async _ =>
                                {
                                    Option<MediaItem> updated = await _searchRepository.GetItemToIndex(incoming.Id);
                                    if (updated.IsSome)
                                    {
                                        await _searchIndex.UpdateItems(
                                            _searchRepository,
                                            new List<MediaItem> { updated.ValueUnsafe() });
                                    }
                                },
                                error =>
                                {
                                    _logger.LogWarning(
                                        "Unable to refresh {Attribute} for media item {Path}. Error: {Error}",
                                        "Statistics",
                                        localPath,
                                        error.Value);

                                    return Task.CompletedTask;
                                });
                        }

                        // TODO: figure out how to rebuild playlists
                    }

                    var incomingMovieIds = validMovies.Map(s => s.ItemId).ToList();
                    var movieIds = existingMovies
                        .Filter(i => !incomingMovieIds.Contains(i.ItemId))
                        .Map(m => m.ItemId)
                        .ToList();
                    List<int> ids = await _movieRepository.RemoveMissingEmbyMovies(library, movieIds);
                    await _searchIndex.RemoveItems(ids);

                    await _mediator.Publish(new LibraryScanProgress(library.Id, 0));
                    _searchIndex.Commit();
                },
                error =>
                {
                    _logger.LogWarning(
                        "Error synchronizing emby library {Path}: {Error}",
                        library.Name,
                        error.Value);

                    return Task.CompletedTask;
                });

            _searchIndex.Commit();
            return Unit.Default;
        }
    }
}