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

// Application + MessageBox aliases live in GlobalUsings.cs (project-wide).
// Don't redeclare here — Roslyn errors with CS1537 on duplicate alias.

namespace TeamsISO.App;

// Split across partial files by responsibility:
//   • App.xaml.cs              — class skeleton, OnStartup (the wiring
//                                pipeline that calls into the partials),
//                                OnExit, CLI arg parser.
//   • App.Bootstrap.cs         — the linear setup steps OnStartup walks
//                                (single-instance gate, NDI interop, engine,
//                                main window, control surface, tray icon,
//                                onboarding, Teams auto-launch).
//   • App.CrashHandlers.cs     — AppDomain / Dispatcher / Task exception
//                                handlers + crash dialog + LogDirectory.
//   • App.UpdateCheckBootstrap.cs — the background update-checker
//                                kickoff (24h-throttled).
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 bool _ownsSingleInstanceMutex;
    private ThreadMessageEventHandler? _bringToFrontHandler;
    private ILoggerFactory? _loggerFactory;
    private NdiInteropPInvoke? _interop;
    private IsoController? _controller;
    private MainViewModel? _viewModel;
    private TeamsISO.App.Services.ControlSurfaceServer? _controlSurface;
    private TeamsISO.App.Services.OscBridge? _oscBridge;
    // _diskSpaceWatcher removed — only existed to auto-disable recording at low free space.
    private TeamsISO.App.Services.TrayIconHost? _trayIcon;

    /// <summary>
    /// REST control surface lifetime. Lives on App so the settings VM can flip
    /// it on/off without us plumbing yet another DI dependency through MainViewModel.
    /// Null between process startup and the OnStartup wire-up, and after OnExit.
    /// </summary>
    internal TeamsISO.App.Services.ControlSurfaceServer? ControlSurface => _controlSurface;

    /// <summary>OSC bridge (UDP) lifetime — same lifecycle pattern as the REST surface.</summary>
    internal TeamsISO.App.Services.OscBridge? OscBridge => _oscBridge;

    /// <summary>Tray-icon host. Exposed so the settings VM can flip the minimize-to-tray toggle.</summary>
    internal TeamsISO.App.Services.TrayIconHost? TrayIcon => _trayIcon;

    [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);

        // Crash diagnostics — wire the three exception channels WPF leaves open by
        // default to a single handler that logs Fatal to Serilog (which has the
        // rolling-daily file sink at %LOCALAPPDATA%\TeamsISO\Logs) and then shows
        // the user a dialog with the log path so they can attach it to a bug
        // report. We deliberately don't catch StackOverflowException or
        // ExecutionEngineException — both are uncatchable in modern .NET; if one
        // fires the OS Watson dialog will take it from here.
        AppDomain.CurrentDomain.UnhandledException += OnAppDomainUnhandled;
        DispatcherUnhandledException += OnDispatcherUnhandled;
        System.Threading.Tasks.TaskScheduler.UnobservedTaskException += OnUnobservedTaskException;

        // Resolve and apply the theme BEFORE any window is shown so we don't
        // paint a dark frame for one tick then flip to light (or vice versa).
        // ThemeManager.Apply swaps Application.Resources.MergedDictionaries
        // in place; DynamicResource refs in WildDragonTheme.xaml re-bind.
        TeamsISO.App.Services.ThemeManager.Current.Apply();

        // Single-instance gate. Implementation in App.Bootstrap.cs; we
        // bail silently if another instance already owns the mutex (the
        // existing instance gets surfaced via the bring-to-front broadcast).
        if (!TryAcquireSingleInstance())
        {
            Shutdown(0);
            return;
        }

        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);

            if (!TryBootstrapNdiInterop())
            {
                Shutdown(2);
                return;
            }

            BootstrapEngine();
            var window = ConstructAndShowMainWindow();
            BootstrapControlSurfaceServices();
            BootstrapTrayIcon(window);
            TryShowOnboarding(window);

            // Parse CLI args BEFORE InitializeAsync so any --apply-preset
            // request overrides the persisted auto-apply preference cleanly.
            ApplyCommandLineArgs(e.Args);

            await _viewModel!.InitializeAsync(CancellationToken.None);

            TryAutoLaunchTeams(logger);
            StartBackgroundUpdateCheck(logger);
        }
        catch (Exception ex)
        {
            // Log the full exception (incl. stack + inner) to Serilog BEFORE the
            // modal MessageBox fires — diagnostic logs are far more useful than a
            // user-pasted "TeamsISO failed to start..." line when triaging a
            // startup crash. The logger may itself have been the failure target
            // so guard the call.
            try { _loggerFactory?.CreateLogger<App>().LogCritical(ex, "OnStartup failed before main loop"); }
            catch { /* defensive */ }
            MessageBox.Show(
                "TeamsISO failed to start.\n\nDetails: " + ex,
                "TeamsISO — startup error",
                MessageBoxButton.OK,
                MessageBoxImage.Error);
            Shutdown(1);
        }
    }

    /// <summary>
    /// Parse the supported CLI flags. Currently:
    ///   <c>--apply-preset NAME</c> — apply the named preset once participants
    ///   populate. Equivalent to running TeamsISO and clicking Presets → select →
    ///   Apply, but driven from a desktop shortcut.
    /// Unrecognized flags are silently ignored — operators using shortcut.lnk
    /// files don't need to fight argument parsers.
    /// </summary>
    private void ApplyCommandLineArgs(string[] args)
    {
        if (_viewModel is null) return;
        for (var i = 0; i < args.Length; i++)
        {
            switch (args[i])
            {
                case "--apply-preset":
                    if (i + 1 < args.Length && !string.IsNullOrEmpty(args[i + 1]))
                    {
                        _viewModel.RequestApplyPresetOnStartup(args[i + 1]);
                        i++; // consume the value
                    }
                    break;
            }
        }
    }

    // Crash handlers (OnAppDomainUnhandled / OnDispatcherUnhandled /
    // OnUnobservedTaskException / TryLogFatal / TryShowCrashDialog / LogDirectory)
    // live in App.CrashHandlers.cs.

    protected override async void OnExit(ExitEventArgs e)
    {
        try
        {
            _trayIcon?.Dispose();
            if (_controlSurface is not null)
                await _controlSurface.DisposeAsync();
            if (_oscBridge is not null)
                await _oscBridge.DisposeAsync();
            _viewModel?.Dispose();
            if (_controller is not null)
                await _controller.DisposeAsync();
            _interop?.Dispose();
            _loggerFactory?.Dispose();
        }
        catch
        {
            // Best-effort shutdown
        }
        finally
        {
            // Unsubscribe the bring-to-front filter so the delegate doesn't outlive
            // the App; ComponentDispatcher is process-static.
            if (_bringToFrontHandler is not null)
            {
                ComponentDispatcher.ThreadFilterMessage -= _bringToFrontHandler;
                _bringToFrontHandler = null;
            }
            // Release the Mutex iff we acquired it. The "lost the race" path above
            // sets _ownsSingleInstanceMutex=false and we skip ReleaseMutex (which
            // would throw ApplicationException on an unowned Mutex).
            try { if (_ownsSingleInstanceMutex) _singleInstanceMutex?.ReleaseMutex(); }
            catch { /* defensive: already-released or invalid handle */ }
            _singleInstanceMutex?.Dispose();
        }
        base.OnExit(e);
    }
}