using System.IO;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
using System.Windows.Threading;
using Microsoft.Extensions.Logging;
using TeamsISO.App.ViewModels;
using TeamsISO.Engine.Controller;
using TeamsISO.Engine.Interop;
using TeamsISO.Engine.Logging;
using TeamsISO.Engine.NdiInterop;
using TeamsISO.Engine.Persistence;
using TeamsISO.Engine.Pipeline;

namespace TeamsISO.App;

public partial class App : Application
{
    /// <summary>
    /// Per-user mutex name. Including the SID-equivalent (the username) ensures two
    /// different Windows users can each run TeamsISO on the same machine, while one
    /// user can't spawn duplicate instances that would contend over the NDI runtime
    /// and the shared %APPDATA%\TeamsISO\config.json.
    /// </summary>
    private static readonly string SingleInstanceMutexName =
        $"Local\\WildDragon.TeamsISO.SingleInstance.{Environment.UserName}";

    private System.Threading.Mutex? _singleInstanceMutex;
    private ILoggerFactory? _loggerFactory;
    private NdiInteropPInvoke? _interop;
    private IsoController? _controller;
    private MainViewModel? _viewModel;

    [DllImport("user32.dll")]
    private static extern uint RegisterWindowMessageW(string lpString);
    [DllImport("user32.dll")]
    private static extern int PostMessageW(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
    [DllImport("user32.dll")]
    private static extern int SendNotifyMessageW(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
    private const IntPtr HWND_BROADCAST = -1;

    protected override async void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        // Single-instance gate: if another TeamsISO is already running for this user,
        // broadcast the bring-to-front message and exit silently. This prevents the
        // NDI/config contention seen during testing where two finders, two senders
        // with the same default name, and two writers to config.json all raced.
        bool createdNew;
        _singleInstanceMutex = new System.Threading.Mutex(initiallyOwned: true, SingleInstanceMutexName, out createdNew);
        if (!createdNew)
        {
            var bringToFront = RegisterWindowMessageW("WildDragon.TeamsISO.BringToFront");
            if (bringToFront != 0)
                SendNotifyMessageW(HWND_BROADCAST, bringToFront, IntPtr.Zero, IntPtr.Zero);
            Shutdown(0);
            return;
        }

        // Listen for the broadcast — if a *new* instance launches and finds us already
        // running, it'll send this message; we surface our window in response.
        var bringToFrontMsg = RegisterWindowMessageW("WildDragon.TeamsISO.BringToFront");
        ComponentDispatcher.ThreadFilterMessage += (ref System.Windows.Interop.MSG msg, ref bool handled) =>
        {
            if (msg.message == (int)bringToFrontMsg && MainWindow is not null)
            {
                if (MainWindow.WindowState == WindowState.Minimized) MainWindow.WindowState = WindowState.Normal;
                MainWindow.Activate();
                MainWindow.Topmost = true;
                MainWindow.Topmost = false;
                handled = true;
            }
        };

        try
        {
            // WPF host: write to both console (visible if attached) and a rolling daily
            // file under %LOCALAPPDATA%\TeamsISO\Logs so users have something to grab when
            // they file an issue.
            _loggerFactory = EngineLogging.CreateDefault(LogLevel.Information);
            var logger = _loggerFactory.CreateLogger<App>();
            logger.LogInformation(
                "TeamsISO.App starting up. Build: {Version}. Process: {Pid}.",
                typeof(App).Assembly.GetName().Version,
                Environment.ProcessId);

            // ---- Preflight: NDI runtime ----
            try
            {
                _interop = new NdiInteropPInvoke(_loggerFactory.CreateLogger<NdiInteropPInvoke>());
            }
            catch (Exception ex)
            {
                MessageBox.Show(
                    "TeamsISO could not initialize the NDI runtime.\n\n" +
                    "Install the NDI Runtime from https://ndi.video/tools/ and try again.\n\n" +
                    "Details: " + ex.Message,
                    "TeamsISO — NDI runtime missing",
                    MessageBoxButton.OK,
                    MessageBoxImage.Error);
                Shutdown(2);
                return;
            }

            // ---- Engine wiring ----
            var configPath = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
                "TeamsISO", "config.json");
            var configStore = new ConfigStore(configPath, _loggerFactory.CreateLogger<ConfigStore>());

            var probe = new NdiRuntimeProbe(_interop, NdiVersion.ExpectedRuntimeVersionPrefix);
            var scaler = new ManagedNearestNeighborFrameScaler();

            var loggerFactoryRef = _loggerFactory;
            var interopRef = _interop;
            IsoPipeline PipelineFactory(IsoPipelineConfig config)
            {
                var clock = new PeriodicTimerFrameClock(config.Settings.FramerateHz);
                return new IsoPipeline(
                    config, interopRef, scaler, clock,
                    ExponentialBackoff.Default,
                    (delay, ct) => Task.Delay(delay, ct),
                    loggerFactoryRef);
            }

            _controller = new IsoController(
                _interop, PipelineFactory, configStore, probe, _loggerFactory);

            _viewModel = new MainViewModel(_controller, Dispatcher);
            var window = new MainWindow(_viewModel);
            window.Show();
            MainWindow = window;

            await _viewModel.InitializeAsync(CancellationToken.None);
        }
        catch (Exception ex)
        {
            MessageBox.Show(
                "TeamsISO failed to start.\n\nDetails: " + ex,
                "TeamsISO — startup error",
                MessageBoxButton.OK,
                MessageBoxImage.Error);
            Shutdown(1);
        }
    }

    protected override async void OnExit(ExitEventArgs e)
    {
        try
        {
            _viewModel?.Dispose();
            if (_controller is not null)
                await _controller.DisposeAsync();
            _interop?.Dispose();
            _loggerFactory?.Dispose();
        }
        catch
        {
            // Best-effort shutdown
        }
        finally
        {
            try { _singleInstanceMutex?.ReleaseMutex(); } catch { /* not owned */ }
            _singleInstanceMutex?.Dispose();
        }
        base.OnExit(e);
    }
}