using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using ErsatzTV.Core;
using ErsatzTV.Core.Domain;
using ErsatzTV.Core.Interfaces.Metadata;
using ErsatzTV.Core.Interfaces.Repositories;
using ErsatzTV.Core.Interfaces.Search;
using ErsatzTV.Core.Search;
using LanguageExt;
using LanguageExt.UnsafeValueAccess;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Documents;
using Lucene.Net.Index;
using Lucene.Net.QueryParsers.Classic;
using Lucene.Net.Sandbox.Queries;
using Lucene.Net.Search;
using Lucene.Net.Store;
using Lucene.Net.Util;
using Microsoft.Extensions.Logging;
using Query = Lucene.Net.Search.Query;

namespace ErsatzTV.Infrastructure.Search
{
    public sealed class SearchIndex : ISearchIndex
    {
        private const LuceneVersion AppLuceneVersion = LuceneVersion.LUCENE_48;

        private const string IdField = "id";
        private const string TypeField = "type";
        private const string ArtistField = "artist";
        private const string TitleField = "title";
        private const string SortTitleField = "sort_title";
        private const string GenreField = "genre";
        private const string TagField = "tag";
        private const string PlotField = "plot";
        private const string LibraryNameField = "library_name";
        private const string TitleAndYearField = "title_and_year";
        private const string JumpLetterField = "jump_letter";
        private const string ReleaseDateField = "release_date";
        private const string StudioField = "studio";
        private const string LanguageField = "language";

        private const string MovieType = "movie";
        private const string ShowType = "show";
        private const string MusicVideoType = "music_video";

        private readonly ILogger<SearchIndex> _logger;

        private FSDirectory _directory;
        private IndexWriter _writer;

        public SearchIndex(ILogger<SearchIndex> logger) => _logger = logger;

        public int Version => 3;

        public Task<bool> Initialize(ILocalFileSystem localFileSystem)
        {
            localFileSystem.EnsureFolderExists(FileSystemLayout.SearchIndexFolder);

            _directory = FSDirectory.Open(FileSystemLayout.SearchIndexFolder);
            var analyzer = new StandardAnalyzer(AppLuceneVersion);
            var indexConfig = new IndexWriterConfig(AppLuceneVersion, analyzer)
                { OpenMode = OpenMode.CREATE_OR_APPEND };
            _writer = new IndexWriter(_directory, indexConfig);

            return Task.FromResult(true);
        }

        public async Task<Unit> Rebuild(ISearchRepository searchRepository, List<int> itemIds)
        {
            foreach (int id in itemIds)
            {
                Option<MediaItem> maybeMediaItem = await searchRepository.GetItemToIndex(id);
                if (maybeMediaItem.IsSome)
                {
                    MediaItem mediaItem = maybeMediaItem.ValueUnsafe();
                    switch (mediaItem)
                    {
                        case Movie movie:
                            UpdateMovie(movie);
                            break;
                        case Show show:
                            UpdateShow(show);
                            break;
                        case MusicVideo musicVideo:
                            UpdateMusicVideo(musicVideo);
                            break;
                    }
                }
            }

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

        public Task<Unit> AddItems(List<MediaItem> items) => UpdateItems(items);

        public Task<Unit> UpdateItems(List<MediaItem> items)
        {
            foreach (MediaItem item in items)
            {
                switch (item)
                {
                    case Movie movie:
                        UpdateMovie(movie);
                        break;
                    case Show show:
                        UpdateShow(show);
                        break;
                    case MusicVideo musicVideo:
                        UpdateMusicVideo(musicVideo);
                        break;
                }
            }

            return Task.FromResult(Unit.Default);
        }

        public Task<Unit> RemoveItems(List<int> ids)
        {
            foreach (int id in ids)
            {
                _writer.DeleteDocuments(new Term(IdField, id.ToString()));
            }

            return Task.FromResult(Unit.Default);
        }

        public Task<SearchResult> Search(string searchQuery, int skip, int limit, string searchField = "")
        {
            if (string.IsNullOrWhiteSpace(searchQuery.Replace("*", string.Empty).Replace("?", string.Empty)))
            {
                return new SearchResult(new List<SearchItem>(), 0).AsTask();
            }

            using DirectoryReader reader = _writer.GetReader(true);
            var searcher = new IndexSearcher(reader);
            int hitsLimit = skip + limit;
            using var analyzer = new StandardAnalyzer(AppLuceneVersion);
            QueryParser parser = !string.IsNullOrWhiteSpace(searchField)
                ? new QueryParser(AppLuceneVersion, searchField, analyzer)
                : new MultiFieldQueryParser(AppLuceneVersion, new[] { TitleField }, analyzer);
            parser.AllowLeadingWildcard = true;
            Query query = ParseQuery(searchQuery, parser);
            var filter = new DuplicateFilter(TitleAndYearField);
            var sort = new Sort(new SortField(SortTitleField, SortFieldType.STRING));
            TopFieldDocs topDocs = searcher.Search(query, filter, hitsLimit, sort, true, true);
            IEnumerable<ScoreDoc> selectedHits = topDocs.ScoreDocs.Skip(skip).Take(limit);

            var searchResult = new SearchResult(
                selectedHits.Map(d => ProjectToSearchItem(searcher.Doc(d.Doc))).ToList(),
                topDocs.TotalHits);

            searchResult.PageMap = GetSearchPageMap(searcher, query, filter, sort, limit);

            return searchResult.AsTask();
        }

        public void Commit() => _writer.Commit();

        public void Dispose()
        {
            _writer?.Dispose();
            _directory?.Dispose();
        }

        private static Option<SearchPageMap> GetSearchPageMap(
            IndexSearcher searcher,
            Query query,
            DuplicateFilter filter,
            Sort sort,
            int limit)
        {
            ScoreDoc[] allDocs = searcher.Search(query, filter, int.MaxValue, sort, true, true).ScoreDocs;
            var letters = new List<char>
            {
                '#', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
                'u', 'v', 'w', 'x', 'y', 'z'
            };
            var map = letters.ToDictionary(letter => letter, _ => 0);

            var current = 0;
            var page = 0;
            while (current < allDocs.Length)
            {
                // walk up by page size (limit)
                page++;
                current += limit;
                if (current > allDocs.Length)
                {
                    current = allDocs.Length;
                }

                char jumpLetter = searcher.Doc(allDocs[current - 1].Doc).Get(JumpLetterField).Head();
                foreach (char letter in letters.Where(l => letters.IndexOf(l) <= letters.IndexOf(jumpLetter)))
                {
                    if (map[letter] == 0)
                    {
                        map[letter] = page;
                    }
                }
            }

            int max = map.Values.Max();
            foreach (char letter in letters.Where(letter => map[letter] == 0))
            {
                map[letter] = max;
            }

            return new SearchPageMap(map);
        }

        private void UpdateMovie(Movie movie)
        {
            Option<MovieMetadata> maybeMetadata = movie.MovieMetadata.HeadOrNone();
            if (maybeMetadata.IsSome)
            {
                MovieMetadata metadata = maybeMetadata.ValueUnsafe();

                try
                {
                    var doc = new Document
                    {
                        new StringField(IdField, movie.Id.ToString(), Field.Store.YES),
                        new StringField(TypeField, MovieType, Field.Store.NO),
                        new TextField(TitleField, metadata.Title, Field.Store.NO),
                        new StringField(SortTitleField, metadata.SortTitle.ToLowerInvariant(), Field.Store.NO),
                        new TextField(LibraryNameField, movie.LibraryPath.Library.Name, Field.Store.NO),
                        new StringField(TitleAndYearField, GetTitleAndYear(metadata), Field.Store.NO),
                        new StringField(JumpLetterField, GetJumpLetter(metadata), Field.Store.YES)
                    };

                    AddLanguages(doc, movie.MediaVersions);

                    if (metadata.ReleaseDate.HasValue)
                    {
                        doc.Add(
                            new StringField(
                                ReleaseDateField,
                                metadata.ReleaseDate.Value.ToString("yyyyMMdd"),
                                Field.Store.NO));
                    }

                    if (!string.IsNullOrWhiteSpace(metadata.Plot))
                    {
                        doc.Add(new TextField(PlotField, metadata.Plot ?? string.Empty, Field.Store.NO));
                    }

                    foreach (Genre genre in metadata.Genres)
                    {
                        doc.Add(new TextField(GenreField, genre.Name, Field.Store.NO));
                    }

                    foreach (Tag tag in metadata.Tags)
                    {
                        doc.Add(new TextField(TagField, tag.Name, Field.Store.NO));
                    }

                    foreach (Studio studio in metadata.Studios)
                    {
                        doc.Add(new TextField(StudioField, studio.Name, Field.Store.NO));
                    }

                    _writer.UpdateDocument(new Term(IdField, movie.Id.ToString()), doc);
                }
                catch (Exception ex)
                {
                    metadata.Movie = null;
                    _logger.LogWarning(ex, "Error indexing movie with metadata {@Metadata}", metadata);
                }
            }
        }

        private void AddLanguages(Document doc, List<MediaVersion> mediaVersions)
        {
            Option<MediaVersion> maybeVersion = mediaVersions.HeadOrNone();
            if (maybeVersion.IsSome)
            {
                MediaVersion version = maybeVersion.ValueUnsafe();
                foreach (string lang in version.Streams.Map(ms => ms.Language).Distinct()
                    .Filter(s => !string.IsNullOrWhiteSpace(s)))
                {
                    doc.Add(new StringField(LanguageField, lang, Field.Store.NO));
                }
            }
        }

        private void UpdateShow(Show show)
        {
            Option<ShowMetadata> maybeMetadata = show.ShowMetadata.HeadOrNone();
            if (maybeMetadata.IsSome)
            {
                ShowMetadata metadata = maybeMetadata.ValueUnsafe();

                try
                {
                    var doc = new Document
                    {
                        new StringField(IdField, show.Id.ToString(), Field.Store.YES),
                        new StringField(TypeField, ShowType, Field.Store.NO),
                        new TextField(TitleField, metadata.Title, Field.Store.NO),
                        new StringField(SortTitleField, metadata.SortTitle.ToLowerInvariant(), Field.Store.NO),
                        new TextField(LibraryNameField, show.LibraryPath.Library.Name, Field.Store.NO),
                        new StringField(TitleAndYearField, GetTitleAndYear(metadata), Field.Store.NO),
                        new StringField(JumpLetterField, GetJumpLetter(metadata), Field.Store.YES)
                    };

                    if (metadata.ReleaseDate.HasValue)
                    {
                        doc.Add(
                            new StringField(
                                ReleaseDateField,
                                metadata.ReleaseDate.Value.ToString("yyyyMMdd"),
                                Field.Store.NO));
                    }

                    if (!string.IsNullOrWhiteSpace(metadata.Plot))
                    {
                        doc.Add(new TextField(PlotField, metadata.Plot ?? string.Empty, Field.Store.NO));
                    }

                    foreach (Genre genre in metadata.Genres)
                    {
                        doc.Add(new TextField(GenreField, genre.Name, Field.Store.NO));
                    }

                    foreach (Tag tag in metadata.Tags)
                    {
                        doc.Add(new TextField(TagField, tag.Name, Field.Store.NO));
                    }

                    foreach (Studio studio in metadata.Studios)
                    {
                        doc.Add(new TextField(StudioField, studio.Name, Field.Store.NO));
                    }

                    _writer.UpdateDocument(new Term(IdField, show.Id.ToString()), doc);
                }
                catch (Exception ex)
                {
                    metadata.Show = null;
                    _logger.LogWarning(ex, "Error indexing show with metadata {@Metadata}", metadata);
                }
            }
        }

        private void UpdateMusicVideo(MusicVideo musicVideo)
        {
            Option<MusicVideoMetadata> maybeMetadata = musicVideo.MusicVideoMetadata.HeadOrNone();
            if (maybeMetadata.IsSome)
            {
                MusicVideoMetadata metadata = maybeMetadata.ValueUnsafe();

                try
                {
                    var doc = new Document
                    {
                        new StringField(IdField, musicVideo.Id.ToString(), Field.Store.YES),
                        new StringField(TypeField, MusicVideoType, Field.Store.NO),
                        new TextField(ArtistField, metadata.Artist, Field.Store.NO),
                        new TextField(TitleField, metadata.Title, Field.Store.NO),
                        new StringField(SortTitleField, metadata.SortTitle.ToLowerInvariant(), Field.Store.NO),
                        new TextField(LibraryNameField, musicVideo.LibraryPath.Library.Name, Field.Store.NO),
                        new StringField(TitleAndYearField, GetTitleAndYear(metadata), Field.Store.NO),
                        new StringField(JumpLetterField, GetJumpLetter(metadata), Field.Store.YES)
                    };

                    AddLanguages(doc, musicVideo.MediaVersions);

                    if (metadata.ReleaseDate.HasValue)
                    {
                        doc.Add(
                            new StringField(
                                ReleaseDateField,
                                metadata.ReleaseDate.Value.ToString("yyyyMMdd"),
                                Field.Store.NO));
                    }

                    if (!string.IsNullOrWhiteSpace(metadata.Plot))
                    {
                        doc.Add(new TextField(PlotField, metadata.Plot ?? string.Empty, Field.Store.NO));
                    }

                    foreach (Genre genre in metadata.Genres)
                    {
                        doc.Add(new TextField(GenreField, genre.Name, Field.Store.NO));
                    }

                    foreach (Tag tag in metadata.Tags)
                    {
                        doc.Add(new TextField(TagField, tag.Name, Field.Store.NO));
                    }

                    foreach (Studio studio in metadata.Studios)
                    {
                        doc.Add(new TextField(StudioField, studio.Name, Field.Store.NO));
                    }

                    _writer.UpdateDocument(new Term(IdField, musicVideo.Id.ToString()), doc);
                }
                catch (Exception ex)
                {
                    metadata.MusicVideo = null;
                    _logger.LogWarning(ex, "Error indexing music video with metadata {@Metadata}", metadata);
                }
            }
        }

        private SearchItem ProjectToSearchItem(Document doc) => new(Convert.ToInt32(doc.Get(IdField)));

        private Query ParseQuery(string searchQuery, QueryParser parser)
        {
            Query query;
            try
            {
                query = parser.Parse(searchQuery.Trim());
            }
            catch (ParseException)
            {
                query = parser.Parse(QueryParserBase.Escape(searchQuery.Trim()));
            }

            return query;
        }

        private static string GetTitleAndYear(Metadata metadata) =>
            $"{metadata.Title}_{metadata.Year}";

        private static string GetJumpLetter(Metadata metadata)
        {
            char c = metadata.SortTitle.ToLowerInvariant().Head();
            return c switch
            {
                (>= 'a' and <= 'z') => c.ToString(),
                _ => "#"
            };
        }
    }
}