using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using System.Timers;
using ConfusedPolarBear.Plugin.IntroSkipper.Configuration;
using MediaBrowser.Common.Extensions;
using MediaBrowser.Controller.Library;
using MediaBrowser.Controller.Session;
using MediaBrowser.Model.Entities;
using MediaBrowser.Model.Plugins;
using MediaBrowser.Model.Session;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Timer = System.Timers.Timer;

namespace ConfusedPolarBear.Plugin.IntroSkipper;

/// <summary>
/// Automatically skip past credit sequences.
/// Commands clients to seek to the end of the credits as soon as they start playing it.
/// </summary>
public class AutoSkipCredits : IHostedService, IDisposable
{
    private readonly object _sentSeekCommandLock = new();

    private ILogger<AutoSkipCredits> _logger;
    private IUserDataManager _userDataManager;
    private ISessionManager _sessionManager;
    private Timer _playbackTimer = new(1000);
    private Dictionary<string, bool> _sentSeekCommand;

    /// <summary>
    /// Initializes a new instance of the <see cref="AutoSkipCredits"/> class.
    /// </summary>
    /// <param name="userDataManager">User data manager.</param>
    /// <param name="sessionManager">Session manager.</param>
    /// <param name="logger">Logger.</param>
    public AutoSkipCredits(
        IUserDataManager userDataManager,
        ISessionManager sessionManager,
        ILogger<AutoSkipCredits> logger)
    {
        _userDataManager = userDataManager;
        _sessionManager = sessionManager;
        _logger = logger;
        _sentSeekCommand = new Dictionary<string, bool>();
    }

    private void AutoSkipCreditChanged(object? sender, BasePluginConfiguration e)
    {
        var configuration = (PluginConfiguration)e;
        var newState = configuration.AutoSkipCredits;
        _logger.LogDebug("Setting playback timer enabled to {NewState}", newState);
        _playbackTimer.Enabled = newState;
    }

    private void UserDataManager_UserDataSaved(object? sender, UserDataSaveEventArgs e)
    {
        var itemId = e.Item.Id;
        var newState = false;
        var episodeNumber = e.Item.IndexNumber.GetValueOrDefault(-1);

        // Ignore all events except playback start & end
        if (e.SaveReason != UserDataSaveReason.PlaybackStart && e.SaveReason != UserDataSaveReason.PlaybackFinished)
        {
            return;
        }

        // Lookup the session for this item.
        SessionInfo? session = null;

        try
        {
            foreach (var needle in _sessionManager.Sessions)
            {
                if (needle.UserId == e.UserId && needle.NowPlayingItem.Id == itemId)
                {
                    session = needle;
                    break;
                }
            }

            if (session == null)
            {
                _logger.LogInformation("Unable to find session for {Item}", itemId);
                return;
            }
        }
        catch (Exception ex) when (ex is NullReferenceException || ex is ResourceNotFoundException)
        {
            return;
        }

        // If this is the first episode in the season, and SkipFirstEpisode is false, pretend that we've already sent the seek command for this playback session.
        if (Plugin.Instance!.Configuration.SkipFirstEpisode && episodeNumber == 1)
        {
            newState = true;
        }

        // Reset the seek command state for this device.
        lock (_sentSeekCommandLock)
        {
            var device = session.DeviceId;

            _logger.LogDebug("Resetting seek command state for session {Session}", device);
            _sentSeekCommand[device] = newState;
        }
    }

    private void PlaybackTimer_Elapsed(object? sender, ElapsedEventArgs e)
    {
        foreach (var session in _sessionManager.Sessions)
        {
            var deviceId = session.DeviceId;
            var itemId = session.NowPlayingItem.Id;
            var position = session.PlayState.PositionTicks / TimeSpan.TicksPerSecond;

            // Don't send the seek command more than once in the same session.
            lock (_sentSeekCommandLock)
            {
                if (_sentSeekCommand.TryGetValue(deviceId, out var sent) && sent)
                {
                    _logger.LogTrace("Already sent seek command for session {Session}", deviceId);
                    continue;
                }
            }

            // Assert that credits were detected for this item.
            if (!Plugin.Instance!.Credits.TryGetValue(itemId, out var credit) || !credit.Valid)
            {
                continue;
            }

            // Seek is unreliable if called at the very end of an episode.
            var adjustedStart = credit.IntroStart + Plugin.Instance.Configuration.SecondsOfCreditsStartToPlay;
            var adjustedEnd = credit.IntroEnd - Plugin.Instance.Configuration.RemainingSecondsOfIntro;

            _logger.LogTrace(
                "Playback position is {Position}, credits run from {Start} to {End}",
                position,
                adjustedStart,
                adjustedEnd);

            if (position < adjustedStart || position > adjustedEnd)
            {
                continue;
            }

            // Notify the user that credits are being skipped for them.
            var notificationText = Plugin.Instance!.Configuration.AutoSkipCreditsNotificationText;
            if (!string.IsNullOrWhiteSpace(notificationText))
            {
                _sessionManager.SendMessageCommand(
                session.Id,
                session.Id,
                new MessageCommand
                {
                    Header = string.Empty,      // some clients require header to be a string instead of null
                    Text = notificationText,
                    TimeoutMs = 2000,
                },
                CancellationToken.None);
            }

            _logger.LogDebug("Sending seek command to {Session}", deviceId);

            _sessionManager.SendPlaystateCommand(
                session.Id,
                session.Id,
                new PlaystateRequest
                {
                    Command = PlaystateCommand.Seek,
                    ControllingUserId = session.UserId.ToString(),
                    SeekPositionTicks = (long)adjustedEnd * TimeSpan.TicksPerSecond,
                },
                CancellationToken.None);

            // Flag that we've sent the seek command so that it's not sent repeatedly
            lock (_sentSeekCommandLock)
            {
                _logger.LogTrace("Setting seek command state for session {Session}", deviceId);
                _sentSeekCommand[deviceId] = true;
            }
        }
    }

    /// <summary>
    /// Dispose.
    /// </summary>
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    /// <summary>
    /// Protected dispose.
    /// </summary>
    /// <param name="disposing">Dispose.</param>
    protected virtual void Dispose(bool disposing)
    {
        if (!disposing)
        {
            return;
        }

        _playbackTimer.Stop();
        _playbackTimer.Dispose();
    }

    /// <inheritdoc />
    public Task StartAsync(CancellationToken cancellationToken)
    {
        _logger.LogDebug("Setting up automatic credit skipping");

        _userDataManager.UserDataSaved += UserDataManager_UserDataSaved;
        Plugin.Instance!.ConfigurationChanged += AutoSkipCreditChanged;

        // Make the timer restart automatically and set enabled to match the configuration value.
        _playbackTimer.AutoReset = true;
        _playbackTimer.Elapsed += PlaybackTimer_Elapsed;

        AutoSkipCreditChanged(null, Plugin.Instance.Configuration);

        return Task.CompletedTask;
    }

    /// <inheritdoc />
    public Task StopAsync(CancellationToken cancellationToken)
    {
        _userDataManager.UserDataSaved -= UserDataManager_UserDataSaved;
        return Task.CompletedTask;
    }
}