using System;
using System.Text.Json;
using System.Threading;
using System.Threading.Tasks;
using System.Timers;
using Jellyfin.Plugin.SmartNotify.Services;
using MediaBrowser.Controller.Entities;
using MediaBrowser.Controller.Entities.Movies;
using MediaBrowser.Controller.Entities.TV;
using MediaBrowser.Controller.Library;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Timer = System.Timers.Timer;

namespace Jellyfin.Plugin.SmartNotify.Notifiers;

/// <summary>
/// Background service that monitors library changes and sends smart notifications.
/// </summary>
public class SmartNotifyBackgroundService : IHostedService, IDisposable
{
    private readonly ILogger<SmartNotifyBackgroundService> _logger;
    private readonly ILibraryManager _libraryManager;
    private readonly ItemHistoryService _historyService;
    private readonly DiscordNotificationService _discordService;
    private Timer? _processTimer;
    private bool _disposed;

    /// <summary>
    /// Initializes a new instance of the <see cref="SmartNotifyBackgroundService"/> class.
    /// </summary>
    public SmartNotifyBackgroundService(
        ILogger<SmartNotifyBackgroundService> logger,
        ILibraryManager libraryManager,
        ItemHistoryService historyService,
        DiscordNotificationService discordService)
    {
        _logger = logger;
        _libraryManager = libraryManager;
        _historyService = historyService;
        _discordService = discordService;
    }

    /// <inheritdoc />
    public Task StartAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("SmartNotify background service starting");

        // Subscribe to library events
        _libraryManager.ItemAdded += OnItemAdded;
        _libraryManager.ItemRemoved += OnItemRemoved;

        // Start the notification processing timer (runs every minute)
        _processTimer = new Timer(60_000);
        _processTimer.Elapsed += ProcessPendingNotifications;
        _processTimer.AutoReset = true;
        _processTimer.Start();

        _logger.LogInformation("SmartNotify is now monitoring library changes");

        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public Task StopAsync(CancellationToken cancellationToken)
    {
        _logger.LogInformation("SmartNotify background service stopping");

        _libraryManager.ItemAdded -= OnItemAdded;
        _libraryManager.ItemRemoved -= OnItemRemoved;

        _processTimer?.Stop();

        return Task.CompletedTask;
    }

    /// <summary>
    /// Called when an item is added to the library.
    /// </summary>
    private void OnItemAdded(object? sender, ItemChangeEventArgs e)
    {
        var item = e.Item;

        // Only process Episodes and Movies
        if (item is not Episode && item is not Movie)
        {
            return;
        }

        _logger.LogDebug("Item added: {Name} (Type: {Type}, ID: {Id})", item.Name, item.GetType().Name, item.Id);

        var config = Plugin.Instance?.Configuration;
        if (config == null)
        {
            return;
        }

        // Check if this type of notification is enabled
        if (item is Episode && !config.EnableEpisodeNotifications)
        {
            return;
        }

        if (item is Movie && !config.EnableMovieNotifications)
        {
            return;
        }

        try
        {
            ProcessNewItem(item);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error processing new item {Name}", item.Name);
        }
    }

    /// <summary>
    /// Processes a newly added item.
    /// </summary>
    private void ProcessNewItem(BaseItem item)
    {
        var config = Plugin.Instance?.Configuration;
        if (config == null)
        {
            return;
        }

        // Check 1: Is this a quality upgrade? (Same content, different file)
        var isUpgrade = _historyService.IsQualityUpgrade(item);

        // Check 2: Is there duplicate content currently in the library?
        // This catches the case where the new file arrives BEFORE the old one is deleted
        var hasDuplicate = _historyService.HasDuplicateContent(item, _libraryManager);

        if (isUpgrade || hasDuplicate)
        {
            _logger.LogInformation(
                "Suppressing notification for {Name} - IsUpgrade: {IsUpgrade}, HasDuplicate: {HasDuplicate}",
                item.Name,
                isUpgrade,
                hasDuplicate);

            if (config.SuppressUpgrades)
            {
                // Just record the item and don't notify
                _historyService.RecordItem(item);
                return;
            }
            // If not suppressing, we could send an "upgrade" notification instead
            // For now, just fall through and send as normal
        }

        // Record this item in our database
        _historyService.RecordItem(item);

        // Create pending notification
        var notification = CreateNotification(item);
        if (notification == null)
        {
            return;
        }

        _historyService.QueueNotification(notification);
        _logger.LogInformation("Queued notification for {Name}", item.Name);
    }

    /// <summary>
    /// Creates a pending notification from a base item.
    /// </summary>
    private PendingNotification? CreateNotification(BaseItem item)
    {
        var config = Plugin.Instance?.Configuration;
        var serverUrl = config?.ServerUrl?.TrimEnd('/') ?? string.Empty;

        var notification = new PendingNotification
        {
            JellyfinItemId = item.Id.ToString(),
            ItemType = item.GetType().Name,
            Name = item.Name,
            QueuedAt = DateTime.UtcNow,
            Type = NotificationType.NewContent,
            ProviderIdsJson = JsonSerializer.Serialize(item.ProviderIds ?? new Dictionary<string, string>()),
            Overview = item.Overview
        };

        // Set image URL
        if (!string.IsNullOrEmpty(serverUrl))
        {
            notification.ImageUrl = $"{serverUrl}/Items/{item.Id}/Images/Primary";
        }

        if (item is Episode episode)
        {
            notification.SeriesName = episode.SeriesName;
            notification.SeriesId = episode.SeriesId.ToString();
            notification.SeasonNumber = episode.ParentIndexNumber;
            notification.EpisodeNumber = episode.IndexNumber;
            notification.Year = episode.ProductionYear;

            // Use series image if episode doesn't have one
            if (!string.IsNullOrEmpty(serverUrl) && episode.SeriesId != Guid.Empty)
            {
                notification.ImageUrl = $"{serverUrl}/Items/{episode.SeriesId}/Images/Primary";
            }
        }
        else if (item is Movie movie)
        {
            notification.Year = movie.ProductionYear;
        }

        return notification;
    }

    /// <summary>
    /// Called when an item is removed from the library.
    /// </summary>
    private void OnItemRemoved(object? sender, ItemChangeEventArgs e)
    {
        // We keep the history record! This is important for detecting upgrades.
        // When old file is deleted after new one is added, we don't want to
        // remove our knowledge of this content.
        _logger.LogDebug("Item removed: {Name} (ID: {Id})", e.Item.Name, e.Item.Id);
    }

    /// <summary>
    /// Processes pending notifications (called by timer).
    /// </summary>
    private async void ProcessPendingNotifications(object? sender, ElapsedEventArgs e)
    {
        try
        {
            var config = Plugin.Instance?.Configuration;
            if (config == null || string.IsNullOrEmpty(config.DiscordWebhookUrl))
            {
                return;
            }

            var delayMinutes = config.NotificationDelayMinutes;
            var groupingWindowMinutes = config.GroupingWindowMinutes;
            var cutoff = DateTime.UtcNow.AddMinutes(-delayMinutes);

            var pendingNotifications = _historyService.GetPendingNotifications(cutoff).ToList();
            if (pendingNotifications.Count == 0)
            {
                return;
            }

            _logger.LogDebug("Processing {Count} pending notifications", pendingNotifications.Count);

            // Group episodes by series
            var episodesBySeries = pendingNotifications
                .Where(n => n.ItemType == "Episode" && !string.IsNullOrEmpty(n.SeriesId))
                .GroupBy(n => n.SeriesId!)
                .ToList();

            // Process each series group
            foreach (var seriesGroup in episodesBySeries)
            {
                var oldestInGroup = seriesGroup.Min(n => n.QueuedAt);
                var groupingCutoff = DateTime.UtcNow.AddMinutes(-groupingWindowMinutes);

                // Only process if the oldest notification is outside the grouping window
                if (oldestInGroup > groupingCutoff)
                {
                    _logger.LogDebug(
                        "Waiting for grouping window for series {SeriesId}, oldest: {Oldest}",
                        seriesGroup.Key,
                        oldestInGroup);
                    continue;
                }

                await _discordService.SendGroupedEpisodeNotificationAsync(
                    seriesGroup,
                    CancellationToken.None);

                var idsToRemove = seriesGroup.Select(n => n.Id).ToList();
                _historyService.RemoveNotifications(idsToRemove);
            }

            // Process movies
            var movies = pendingNotifications
                .Where(n => n.ItemType == "Movie")
                .ToList();

            foreach (var movie in movies)
            {
                await _discordService.SendMovieNotificationAsync(movie, CancellationToken.None);
                _historyService.RemoveNotifications(new[] { movie.Id });
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error processing pending notifications");
        }
    }

    /// <inheritdoc />
    public void Dispose()
    {
        if (!_disposed)
        {
            _processTimer?.Dispose();
            _disposed = true;
        }
    }
}