using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using System.Timers;
using MediaBrowser.Controller.Library;
using MediaBrowser.Controller.Plugins;
using MediaBrowser.Controller.Session;
using MediaBrowser.Model.Entities;
using MediaBrowser.Model.Session;
using Microsoft.Extensions.Logging;

namespace ConfusedPolarBear.Plugin.IntroSkipper;

/// <summary>
/// Automatically skip past introduction sequences.
/// Commands clients to seek to the end of the intro as soon as they start playing it.
/// </summary>
public class AutoSkip : IServerEntryPoint
{
    private readonly object _sentSeekCommandLock = new();

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

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

    /// <summary>
    /// If introduction auto skipping is enabled, set it up.
    /// </summary>
    /// <returns>Task.</returns>
    public Task RunAsync()
    {
        if (!Plugin.Instance!.Configuration.AutoSkip)
        {
            _logger.LogDebug("Not setting up automatic skipping");
            return Task.CompletedTask;
        }

        _logger.LogDebug("Setting up automatic skipping");

        _userDataManager.UserDataSaved += UserDataManager_UserDataSaved;

        _playbackTimer.AutoReset = true;
        _playbackTimer.Elapsed += PlaybackTimer_Elapsed;
        _playbackTimer.Start();

        return Task.CompletedTask;
    }

    private void UserDataManager_UserDataSaved(object? sender, UserDataSaveEventArgs e)
    {
        var itemId = e.Item.Id;

        // 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 (NullReferenceException)
        {
            return;
        }

        // 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] = false;
        }
    }

    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[deviceId])
                {
                    _logger.LogTrace("Already sent seek command for session {Session}", deviceId);
                    continue;
                }
            }

            // Assert that an intro was detected for this item.
            if (!Plugin.Instance!.Intros.TryGetValue(itemId, out var intro) || !intro.Valid)
            {
                continue;
            }

            // Seek is unreliable if called at the very start of an episode.
            var adjustedStart = Math.Max(5, intro.IntroStart);

            _logger.LogTrace(
                "Playback position is {Position}, intro runs from {Start} to {End}",
                position,
                adjustedStart,
                intro.IntroEnd);

            if (position < adjustedStart || position > intro.IntroEnd)
            {
                continue;
            }

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

            var seekCommand = new PlaystateRequest
            {
                Command = PlaystateCommand.Seek,
                ControllingUserId = session.UserId.ToString("N"),
                SeekPositionTicks = (long)intro.IntroEnd * TimeSpan.TicksPerSecond,
            };

            _sessionManager.SendPlaystateCommand(session.Id, session.Id, seekCommand, 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;
        }

        _userDataManager.UserDataSaved -= UserDataManager_UserDataSaved;
        _playbackTimer.Stop();
        _playbackTimer.Dispose();
    }
}