using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Net.Sockets;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;

namespace Jellyfin.Plugin.CinemaTrailers4Jellyfins.Services
{
    public record TmdbVideo(string Key, string Name, string Language, bool Official, int Size);

    public record TmdbMediaResult(int Id, string Title, string ReleaseDate)
    {
        public int? Year => DateTime.TryParse(ReleaseDate, out var d) ? d.Year : (int?)null;
    }

    public record TmdbMediaMetadata(IReadOnlyList<string> Genres, string? Certification);

    public class TmdbService : IDisposable
    {
        private readonly HttpClient _httpClient;
        private readonly ILogger<TmdbService> _logger;
        private const string BaseUrl = "https://api.themoviedb.org/3";

        public TmdbService(ILogger<TmdbService> logger)
        {
            _logger = logger;

            // Force IPv4 to avoid ~80s delay when IPv6 is unreachable (Happy Eyeballs fallback).
            var handler = new SocketsHttpHandler
            {
                ConnectCallback = async (ctx, ct) =>
                {
                    var entry = await Dns.GetHostEntryAsync(ctx.DnsEndPoint.Host, AddressFamily.InterNetwork, ct).ConfigureAwait(false);
                    var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                    socket.NoDelay = true;
                    try
                    {
                        await socket.ConnectAsync(entry.AddressList[0], ctx.DnsEndPoint.Port, ct).ConfigureAwait(false);
                        return new NetworkStream(socket, ownsSocket: true);
                    }
                    catch
                    {
                        socket.Dispose();
                        throw;
                    }
                }
            };
            _httpClient = new HttpClient(handler) { Timeout = TimeSpan.FromSeconds(30) };
        }

        public void Dispose() => _httpClient.Dispose();

        // JWT Read Access Tokens start with "eyJ"; v3 short keys (32 hex chars) use ?api_key=.
        private static void ApplyAuth(HttpRequestMessage request, string apiKey)
        {
            if (apiKey.StartsWith("eyJ", StringComparison.Ordinal))
            {
                request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", apiKey);
            }
            else
            {
                var uri = request.RequestUri!.ToString();
                var separator = uri.Contains('?') ? "&" : "?";
                request.RequestUri = new Uri($"{uri}{separator}api_key={apiKey}");
            }
        }

        /// <summary>
        /// Fetches candidate movies from the configured TMDB sources, optionally filtered
        /// by a minimum release date. Deduplicates across sources by TMDB ID.
        /// </summary>
        public Task<List<TmdbMediaResult>> GetCandidateMoviesAsync(
            Configuration.PluginConfiguration config,
            CancellationToken ct)
        {
            var sources = new List<string>();
            if (config.SourceNowPlaying) sources.Add("now_playing");
            if (config.SourceUpcoming)   sources.Add("upcoming");
            if (config.SourcePopular)    sources.Add("popular");
            if (config.SourceTopRated)   sources.Add("top_rated");

            return GetCandidatesAsync("movie", sources, config, ct);
        }

        /// <summary>
        /// Fetches candidate TV shows from the configured TMDB sources, optionally filtered
        /// by a minimum first-air date. Deduplicates across sources by TMDB ID.
        /// </summary>
        public Task<List<TmdbMediaResult>> GetCandidateTvShowsAsync(
            Configuration.PluginConfiguration config,
            CancellationToken ct)
        {
            var sources = new List<string>();
            if (config.SourceTvAiringToday) sources.Add("airing_today");
            if (config.SourceTvOnTheAir)    sources.Add("on_the_air");
            if (config.SourceTvPopular)     sources.Add("popular");
            if (config.SourceTvTopRated)    sources.Add("top_rated");

            return GetCandidatesAsync("tv", sources, config, ct);
        }

        private async Task<List<TmdbMediaResult>> GetCandidatesAsync(
            string mediaType,
            List<string> sourceEndpoints,
            Configuration.PluginConfiguration config,
            CancellationToken ct)
        {
            DateTime? releasedAfter = config.ReleaseDateRangeMonths > 0
                ? DateTime.UtcNow.AddMonths(-config.ReleaseDateRangeMonths)
                : null;

            var seen = new HashSet<int>();
            var results = new List<TmdbMediaResult>();

            foreach (var endpoint in sourceEndpoints)
            {
                var items = await FetchSourcePagesAsync(mediaType, endpoint, config.TmdbApiKey, releasedAfter, config.MaxPagesPerSource, ct)
                    .ConfigureAwait(false);

                foreach (var item in items)
                {
                    if (seen.Add(item.Id))
                        results.Add(item);
                }
            }

            return results;
        }

        private async Task<List<TmdbMediaResult>> FetchSourcePagesAsync(
            string mediaType,
            string endpoint,
            string apiKey,
            DateTime? releasedAfter,
            int maxPages,
            CancellationToken ct)
        {
            var results = new List<TmdbMediaResult>();

            // Movies use "title"/"release_date"; TV shows use "name"/"first_air_date".
            var titleField = mediaType == "movie" ? "title" : "name";
            var dateField = mediaType == "movie" ? "release_date" : "first_air_date";

            for (int page = 1; page <= maxPages; page++)
            {
                ct.ThrowIfCancellationRequested();

                try
                {
                    var url = $"{BaseUrl}/{mediaType}/{endpoint}?language=en-US&page={page}";
                    using var request = new HttpRequestMessage(HttpMethod.Get, url);
                    ApplyAuth(request, apiKey);
                    using var response = await _httpClient.SendAsync(request, ct).ConfigureAwait(false);
                    response.EnsureSuccessStatusCode();
                    var json = await response.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
                    using var doc = JsonDocument.Parse(json);

                    var pageResults = doc.RootElement.GetProperty("results");
                    int totalPages = doc.RootElement.GetProperty("total_pages").GetInt32();
                    bool anyInRange = false;

                    foreach (var entry in pageResults.EnumerateArray())
                    {
                        var releaseDate = entry.TryGetProperty(dateField, out var rd) ? rd.GetString() ?? string.Empty : string.Empty;
                        var title = entry.TryGetProperty(titleField, out var t) ? t.GetString() ?? string.Empty : string.Empty;
                        var id = entry.GetProperty("id").GetInt32();

                        if (releasedAfter.HasValue && DateTime.TryParse(releaseDate, out var parsed))
                        {
                            if (parsed < releasedAfter.Value) continue;
                        }

                        anyInRange = true;
                        results.Add(new TmdbMediaResult(id, title, releaseDate));
                    }

                    if (page >= totalPages || (releasedAfter.HasValue && !anyInRange))
                        break;
                }
                catch (OperationCanceledException)
                {
                    throw;
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, "|CinemaTrailers4Jellyfins| Failed to fetch TMDB source '{MediaType}/{Endpoint}' page {Page}", mediaType, endpoint, page);
                    break;
                }
            }

            return results;
        }

        public async Task<string?> SearchMovieAsync(string title, int? year, string apiKey, CancellationToken ct)
        {
            try
            {
                var url = $"{BaseUrl}/search/movie?query={Uri.EscapeDataString(title)}&language=en-US";
                if (year.HasValue) url += $"&year={year.Value}";
                using var request = new HttpRequestMessage(HttpMethod.Get, url);
                ApplyAuth(request, apiKey);
                using var response = await _httpClient.SendAsync(request, ct).ConfigureAwait(false);
                response.EnsureSuccessStatusCode();
                var json = await response.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
                using var doc = JsonDocument.Parse(json);
                var res = doc.RootElement.GetProperty("results");
                if (res.GetArrayLength() > 0)
                    return res[0].GetProperty("id").GetInt32().ToString();
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                _logger.LogError(ex, "|CinemaTrailers4Jellyfins| TMDB search failed for '{Title}'", title);
            }
            return null;
        }

        /// <summary>
        /// Returns the genre names and US certification for a movie or TV show
        /// (e.g. PG-13 for movies, TV-14 for TV shows). Movies use a single
        /// /movie/{id}?append_to_response=release_dates call; TV shows use
        /// /tv/{id}?append_to_response=content_ratings.
        /// </summary>
        public async Task<TmdbMediaMetadata> GetMediaMetadataAsync(
            string mediaType,
            string tmdbId,
            string apiKey,
            CancellationToken ct)
        {
            try
            {
                var appendField = mediaType == "movie" ? "release_dates" : "content_ratings";
                var url = $"{BaseUrl}/{mediaType}/{tmdbId}?append_to_response={appendField}&language=en-US";
                using var request = new HttpRequestMessage(HttpMethod.Get, url);
                ApplyAuth(request, apiKey);
                using var response = await _httpClient.SendAsync(request, ct).ConfigureAwait(false);
                response.EnsureSuccessStatusCode();
                var json = await response.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
                using var doc = JsonDocument.Parse(json);

                var genres = new List<string>();
                if (doc.RootElement.TryGetProperty("genres", out var genreArr))
                {
                    foreach (var g in genreArr.EnumerateArray())
                    {
                        if (g.TryGetProperty("name", out var name))
                        {
                            var genreName = name.GetString();
                            if (!string.IsNullOrEmpty(genreName))
                                genres.Add(genreName);
                        }
                    }
                }

                string? certification = mediaType == "movie"
                    ? GetMovieCertification(doc)
                    : GetTvCertification(doc);

                return new TmdbMediaMetadata(genres.AsReadOnly(), certification);
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                _logger.LogError(ex, "|CinemaTrailers4Jellyfins| GetMediaMetadata failed for {MediaType} TMDB ID {Id}", mediaType, tmdbId);
                return new TmdbMediaMetadata(Array.Empty<string>(), null);
            }
        }

        // Finds the US theatrical certification (G, PG, PG-13, R, NC-17) from release_dates.
        private static string? GetMovieCertification(JsonDocument doc)
        {
            if (!doc.RootElement.TryGetProperty("release_dates", out var releaseDates)
                || !releaseDates.TryGetProperty("results", out var rdResults))
                return null;

            foreach (var country in rdResults.EnumerateArray())
            {
                if (!country.TryGetProperty("iso_3166_1", out var iso)
                    || !string.Equals(iso.GetString(), "US", StringComparison.OrdinalIgnoreCase))
                    continue;

                if (!country.TryGetProperty("release_dates", out var dates))
                    return null;

                foreach (var date in dates.EnumerateArray())
                {
                    if (!date.TryGetProperty("certification", out var cert))
                        continue;
                    var certStr = cert.GetString();
                    if (!string.IsNullOrWhiteSpace(certStr))
                        return certStr;
                }

                return null;
            }

            return null;
        }

        // Finds the US TV content rating (TV-Y, TV-PG, TV-14, TV-MA, etc.) from content_ratings.
        private static string? GetTvCertification(JsonDocument doc)
        {
            if (!doc.RootElement.TryGetProperty("content_ratings", out var contentRatings)
                || !contentRatings.TryGetProperty("results", out var crResults))
                return null;

            foreach (var country in crResults.EnumerateArray())
            {
                if (!country.TryGetProperty("iso_3166_1", out var iso)
                    || !string.Equals(iso.GetString(), "US", StringComparison.OrdinalIgnoreCase))
                    continue;

                if (!country.TryGetProperty("rating", out var rating))
                    return null;

                var ratingStr = rating.GetString();
                return string.IsNullOrWhiteSpace(ratingStr) ? null : ratingStr;
            }

            return null;
        }

        public async Task<List<TmdbVideo>> GetTrailersAsync(
            string mediaType,
            string tmdbId,
            string apiKey,
            IReadOnlySet<string>? allowedLanguages,
            CancellationToken ct)
        {
            try
            {
                // No language filter on the URL — we want all available trailers so we can
                // filter by iso_639_1 ourselves based on the user's language preference.
                var url = $"{BaseUrl}/{mediaType}/{tmdbId}/videos";
                using var request = new HttpRequestMessage(HttpMethod.Get, url);
                ApplyAuth(request, apiKey);
                using var response = await _httpClient.SendAsync(request, ct).ConfigureAwait(false);
                response.EnsureSuccessStatusCode();
                var json = await response.Content.ReadAsStringAsync(ct).ConfigureAwait(false);
                using var doc = JsonDocument.Parse(json);

                var videos = new List<TmdbVideo>();
                foreach (var result in doc.RootElement.GetProperty("results").EnumerateArray())
                {
                    var type = result.GetProperty("type").GetString();
                    var site = result.GetProperty("site").GetString();
                    if (!string.Equals(type, "Trailer", StringComparison.OrdinalIgnoreCase)
                        || !string.Equals(site, "YouTube", StringComparison.OrdinalIgnoreCase))
                        continue;

                    var key = result.GetProperty("key").GetString();
                    if (string.IsNullOrEmpty(key)) continue;

                    var lang = result.TryGetProperty("iso_639_1", out var l) ? (l.GetString() ?? string.Empty) : string.Empty;

                    if (allowedLanguages != null && allowedLanguages.Count > 0 && !allowedLanguages.Contains(lang))
                        continue;

                    videos.Add(new TmdbVideo(
                        key,
                        result.GetProperty("name").GetString() ?? "Trailer",
                        lang,
                        result.GetProperty("official").GetBoolean(),
                        result.GetProperty("size").GetInt32()));
                }

                return videos
                    .OrderByDescending(v => v.Official)
                    .ThenByDescending(v => v.Size)
                    .ToList();
            }
            catch (OperationCanceledException) { throw; }
            catch (Exception ex)
            {
                _logger.LogError(ex, "|CinemaTrailers4Jellyfins| GetTrailers failed for {MediaType} TMDB ID {Id}", mediaType, tmdbId);
                return new List<TmdbVideo>();
            }
        }
    }
}