using System.Diagnostics;
using SpdUp.Core;
using SpdUp.Models;

namespace SpdUp.Services;

/// <summary>
/// Detects running games and known launchers.
/// </summary>
public sealed class GameDetectionService : IDisposable
{
    private readonly Timer _pollTimer;
    private readonly AppSettings _settings;
    private readonly HashSet<string> _knownGameProcesses = new(StringComparer.OrdinalIgnoreCase);
    private string? _detectedGameProcess;

    public event Action<string>? GameStarted;
    public event Action<string>? GameStopped;

    /// <summary>
    /// Well-known launcher processes that indicate a game may launch.
    /// </summary>
    private static readonly HashSet<string> LauncherProcesses = new(StringComparer.OrdinalIgnoreCase)
    {
        "steam", "steamwebhelper",
        "EpicGamesLauncher",
        "Battle.net", "Agent"
    };

    /// <summary>
    /// Heuristic: processes that look like games (high-memory GPU-using apps not in system dirs).
    /// </summary>
    private static readonly HashSet<string> ExcludedProcessNames = new(StringComparer.OrdinalIgnoreCase)
    {
        "explorer", "svchost", "System", "Idle", "csrss", "smss", "lsass",
        "services", "wininit", "winlogon", "dwm", "taskhostw", "RuntimeBroker",
        "ShellExperienceHost", "SearchHost", "SearchIndexer", "fontdrvhost",
        "conhost", "dllhost", "sihost", "ctfmon", "TextInputHost",
        "SecurityHealthSystray", "SecurityHealthService",
        "devenv", "Code", "chrome", "msedge", "firefox", "Discord",
        "Spotify", "slack", "Teams"
    };

    public GameDetectionService(AppSettings settings)
    {
        _settings = settings;

        // Build known game process name set from settings.
        foreach (var g in _settings.Games)
        {
            if (!string.IsNullOrWhiteSpace(g.ProcessName))
                _knownGameProcesses.Add(g.ProcessName);
        }

        _pollTimer = new Timer(PollForGames, null, Timeout.Infinite, Timeout.Infinite);
    }

    public string? CurrentGameProcess => _detectedGameProcess;

    public void Start(int intervalMs = 3000)
    {
        _pollTimer.Change(0, intervalMs);
        Logger.Info("Game detection started.");
    }

    public void Stop()
    {
        _pollTimer.Change(Timeout.Infinite, Timeout.Infinite);
        Logger.Info("Game detection stopped.");
    }

    public void AddGameProcess(string processName)
    {
        _knownGameProcesses.Add(processName);
    }

    private void PollForGames(object? state)
    {
        try
        {
            var running = Process.GetProcesses();
            string? foundGame = null;

            // First: check known game processes
            foreach (var proc in running)
            {
                try
                {
                    if (_knownGameProcesses.Contains(proc.ProcessName))
                    {
                        foundGame = proc.ProcessName;
                        break;
                    }
                }
                catch { /* access denied */ }
                finally { proc.Dispose(); }
            }

            // Second: heuristic – detect GPU-heavy, non-system, non-launcher processes
            if (foundGame is null)
            {
                foreach (var proc in Process.GetProcesses())
                {
                    try
                    {
                        if (ExcludedProcessNames.Contains(proc.ProcessName)) continue;
                        if (LauncherProcesses.Contains(proc.ProcessName)) continue;
                        if (proc.Id <= 4) continue;

                        // Heuristic: >300 MB working set and has a main window => likely a game
                        if (proc.WorkingSet64 > 300_000_000 && proc.MainWindowHandle != IntPtr.Zero)
                        {
                            // Check it's not from system folders
                            try
                            {
                                var path = proc.MainModule?.FileName;
                                if (path is not null &&
                                    !path.StartsWith(Environment.GetFolderPath(Environment.SpecialFolder.Windows), StringComparison.OrdinalIgnoreCase))
                                {
                                    foundGame = proc.ProcessName;
                                    break;
                                }
                            }
                            catch { /* access denied */ }
                        }
                    }
                    catch { }
                    finally { proc.Dispose(); }
                }
            }

            // State machine: detect start / stop
            if (foundGame is not null && _detectedGameProcess is null)
            {
                _detectedGameProcess = foundGame;
                Logger.Info($"Game detected: {foundGame}");
                GameStarted?.Invoke(foundGame);
            }
            else if (foundGame is null && _detectedGameProcess is not null)
            {
                var prev = _detectedGameProcess;
                _detectedGameProcess = null;
                Logger.Info($"Game stopped: {prev}");
                GameStopped?.Invoke(prev);
            }
        }
        catch (Exception ex)
        {
            Logger.Error("Game detection poll error", ex);
        }
    }

    public void Dispose()
    {
        _pollTimer.Dispose();
    }
}