using System.IO;
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 username (acting as a SID proxy) 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.
    ///
    /// The "Global\" prefix puts the named object in the system-wide namespace
    /// (not session-local or integrity-isolated). This matters because when an
    /// admin user has UAC effectively disabled, launches from different parents
    /// (elevated File Explorer, non-elevated shell, etc.) can land in slightly
    /// different security contexts. A "Local\" mutex was being created in
    /// different views per integrity level on some boxes, letting two TeamsISO
    /// instances run concurrently — the second's REST surface couldn't bind port
    /// 9755 (already held) and its Serilog file sink couldn't open the daily log
    /// (already held with shared=false), producing a window that looked like
    /// the app but had no engine attached. Global\ closes that gap.
    /// </summary>
    private static readonly string SingleInstanceMutexName =
        $"Global\\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)
    {
        // RAW TRACE — captures startup BEFORE Serilog comes up. Helps diagnose
        // launches where the Serilog log stays empty (silent file-sink failure,
        // pre-logger crash, weird parent-spawn environment, etc.). Writes to
        // %LOCALAPPDATA%\TeamsISO\startup-trace.log.
        var parentName = "(unknown)";
        try { parentName = TryGetParentProcessName() ?? "(null)"; } catch { }
        StartupTrace.Write($"OnStartup ENTER. exe={Environment.ProcessPath} parent={parentName} args=[{string.Join(' ', e.Args)}]");
        try
        {
            using var id = System.Security.Principal.WindowsIdentity.GetCurrent();
            var pr = new System.Security.Principal.WindowsPrincipal(id);
            StartupTrace.Write($"identity user={id.Name} isAdmin={pr.IsInRole(System.Security.Principal.WindowsBuiltInRole.Administrator)} integrity-token={id.User}");
        }
        catch (Exception ex) { StartupTrace.Write($"identity probe FAILED: {ex}"); }

        base.OnStartup(e);
        StartupTrace.Write("base.OnStartup returned");

        // De-elevation check — see ShouldDeElevate doc. Trace records the decision.
        bool deElev = false;
        string[] relaunchArgs = e.Args;
        try { deElev = ShouldDeElevate(e.Args, out relaunchArgs); } catch (Exception ex) { StartupTrace.Write($"ShouldDeElevate THREW: {ex}"); }
        StartupTrace.Write($"ShouldDeElevate decision: {deElev}");
        if (deElev)
        {
            var didExit = TryDeElevateAndExit(relaunchArgs);
            if (didExit)
            {
                // Shutdown(0) was issued; let WPF tear us down. No more code runs.
                return;
            }
            // Spawn failed — fall through to normal startup as a fallback so the
            // operator at least sees a window. They may hit the elevated-launch
            // bug (no participants) but that's better than nothing.
            StartupTrace.Write("de-elevate spawn failed — falling through to normal startup as fallback");
        }

        // Crash diagnostics — wire the three exception channels WPF leaves open by
        // default to a single handler that logs Fatal to Serilog.
        AppDomain.CurrentDomain.UnhandledException += OnAppDomainUnhandled;
        DispatcherUnhandledException += OnDispatcherUnhandled;
        System.Threading.Tasks.TaskScheduler.UnobservedTaskException += OnUnobservedTaskException;
        StartupTrace.Write("crash handlers registered");

        try { TeamsISO.App.Services.ThemeManager.Current.Apply(); StartupTrace.Write("ThemeManager.Apply OK"); }
        catch (Exception ex) { StartupTrace.Write($"ThemeManager.Apply THREW: {ex}"); }

        // Single-instance gate. Trace the mutex acquisition.
        bool acquired = false;
        try { acquired = TryAcquireSingleInstance(); } catch (Exception ex) { StartupTrace.Write($"TryAcquireSingleInstance THREW: {ex}"); }
        StartupTrace.Write($"TryAcquireSingleInstance returned: {acquired}");
        if (!acquired)
        {
            StartupTrace.Write("not first instance — Shutdown(0)");
            Shutdown(0);
            return;
        }

        try
        {
            StartupTrace.Write("Bootstrap try-block ENTER");
            _loggerFactory = EngineLogging.CreateDefault(LogLevel.Information);
            StartupTrace.Write("EngineLogging.CreateDefault OK");
            var logger = _loggerFactory.CreateLogger<App>();
            logger.LogInformation(
                "TeamsISO.App starting up. Build: {Version}. Process: {Pid}.",
                typeof(App).Assembly.GetName().Version,
                Environment.ProcessId);
            StartupTrace.Write("Serilog first write attempted");

            if (!TryBootstrapNdiInterop())
            {
                StartupTrace.Write("TryBootstrapNdiInterop returned false — Shutdown(2)");
                Shutdown(2);
                return;
            }
            StartupTrace.Write("TryBootstrapNdiInterop OK");

            BootstrapEngine();
            StartupTrace.Write("BootstrapEngine OK");
            var window = ConstructAndShowMainWindow();
            StartupTrace.Write("ConstructAndShowMainWindow OK (window shown)");
            BootstrapControlSurfaceServices();
            StartupTrace.Write("BootstrapControlSurfaceServices OK");
            BootstrapTrayIcon(window);
            StartupTrace.Write("BootstrapTrayIcon OK");
            TryShowOnboarding(window);
            StartupTrace.Write("TryShowOnboarding returned");

            ApplyCommandLineArgs(e.Args);
            StartupTrace.Write("ApplyCommandLineArgs OK");

            StartupTrace.Write("about to await _viewModel.InitializeAsync");
            await _viewModel!.InitializeAsync(CancellationToken.None);
            StartupTrace.Write("_viewModel.InitializeAsync COMPLETED");

            TryAutoLaunchTeams(logger);
            StartBackgroundUpdateCheck(logger);
            StartupTrace.Write("OnStartup COMPLETE");

            // 5-second post-init participant probe — tells us whether discovery
            // is actually producing rows once the engine is up.
            _ = Task.Run(async () =>
            {
                await Task.Delay(5000);
                try
                {
                    var n = await Dispatcher.InvokeAsync(() => _viewModel?.Participants.Count ?? -1);
                    StartupTrace.Write($"+5s after init: vm.Participants.Count={n}");
                }
                catch (Exception ex) { StartupTrace.Write($"+5s probe THREW: {ex.Message}"); }
            });
        }
        catch (Exception ex)
        {
            StartupTrace.Write($"OnStartup CATCH: {ex}");
            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>
    /// Returns true when we need to re-spawn ourselves with a non-elevated
    /// medium-integrity token. Rule:
    /// <list type="number">
    ///   <item>If we've already been relaunched once (<c>--relaunched</c>
    ///         marker present in args), DO NOT demote again. Strip the
    ///         marker from forwardArgs so it doesn't leak further.</item>
    ///   <item>If our token is elevated (Administrators group active),
    ///         demote — full stop, regardless of parent.</item>
    /// </list>
    /// <para>
    /// The earlier "only if parent == explorer.exe" heuristic was too narrow:
    /// the operator's broken spawn path on this dev box is double-clicking
    /// TeamsISO.exe from an elevated File Explorer, which Windows turns into
    /// a CreateProcess where the parent record is not always explorer (it
    /// depends on Windows version, shell extension state, and whether the
    /// click went through the shell namespace cache). Demoting whenever we
    /// see an elevated token is safer and cheaper than trying to disambiguate
    /// the spawn chain. The cost is one extra millisecond on launch + a brief
    /// console flash from runas; the win is that NDI discovery actually works.
    /// </para>
    /// <para>
    /// If you ever need to run TeamsISO elevated on purpose (debugging some
    /// admin-only API path), pass <c>--keep-elevation</c> on the command line
    /// to bypass this check.
    /// </para>
    /// </summary>
    private const string RelaunchEnvVar = "TEAMSISO_RELAUNCHED";

    private static bool ShouldDeElevate(string[] args, out string[] forwardArgs)
    {
        forwardArgs = args;
        // Already relaunched once — don't loop. The marker is an env var
        // (NOT a CLI arg) because runas.exe /trustlevel:0x20000 fails with
        // exit code 1 when extra args follow the program path; the env var
        // is inherited cleanly across the runas boundary.
        if (string.Equals(Environment.GetEnvironmentVariable(RelaunchEnvVar), "1", StringComparison.Ordinal))
        {
            // Clear it so a future legitimately-elevated launch isn't suppressed.
            Environment.SetEnvironmentVariable(RelaunchEnvVar, null);
            return false;
        }
        // Explicit opt-out for power users.
        if (Array.IndexOf(args, "--keep-elevation") >= 0)
        {
            forwardArgs = args.Where(a => a != "--keep-elevation").ToArray();
            return false;
        }
        // The whole reason for the check — are we elevated?
        try
        {
            using var identity = System.Security.Principal.WindowsIdentity.GetCurrent();
            var principal = new System.Security.Principal.WindowsPrincipal(identity);
            return principal.IsInRole(System.Security.Principal.WindowsBuiltInRole.Administrator);
        }
        catch { return false; }
    }

    /// <summary>
    /// Look up our parent process's image name (without extension). Returns
    /// null if it can't be determined (PID gone, denied, etc.).
    /// </summary>
    private static string? TryGetParentProcessName()
    {
        try
        {
            var pid = Environment.ProcessId;
            using var search = new System.Management.ManagementObjectSearcher(
                $"SELECT ParentProcessId FROM Win32_Process WHERE ProcessId={pid}");
            foreach (var m in search.Get())
            {
                var ppid = Convert.ToInt32(m["ParentProcessId"]);
                using var parent = System.Diagnostics.Process.GetProcessById(ppid);
                return parent.ProcessName;
            }
        }
        catch { /* fall through */ }
        return null;
    }

    /// <summary>
    /// Re-launch TeamsISO via <c>runas.exe /trustlevel:0x20000</c>. The
    /// trustlevel argument requests a medium-integrity restricted token —
    /// even when the caller (us) is elevated, the spawned child runs at
    /// medium integrity. This sidesteps the elevation that was tripping
    /// NDI Find. After the spawn, <see cref="Application.Shutdown(int)"/>
    /// so only the medium-integrity child remains.
    /// </summary>
    /// <returns>true if a child was spawned and the caller should Shutdown;
    /// false if the spawn failed and the caller should fall through to
    /// normal (elevated) startup.</returns>
    private bool TryDeElevateAndExit(string[] forwardArgs)
    {
        try
        {
            var exePath = System.Diagnostics.Process.GetCurrentProcess().MainModule?.FileName;
            if (string.IsNullOrEmpty(exePath))
            {
                StartupTrace.Write("de-elevate: exePath empty, giving up");
                return false;
            }
            StartupTrace.Write($"de-elevate: spawning runas with target {exePath}");

            var quotedExe = "\"" + exePath + "\"";
            // runas /trustlevel:0x20000 rejects any args after the program
            // path (returns exit 1). Pass ONLY the path; relay re-launch
            // state via the TEAMSISO_RELAUNCHED env var, which runas
            // inherits and propagates to the spawned child.
            // Operator CLI args (e.g. --apply-preset NAME) are not
            // forwarded across de-elevation for the same reason; this is
            // an acceptable tradeoff because the elevated launch was
            // probably an Explorer double-click with no args anyway.

            // Find runas.exe explicitly under System32 (the native 64-bit path).
            var systemRunas = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "runas.exe");
            var runasPath = File.Exists(systemRunas) ? systemRunas : "runas.exe";

            var psi = new System.Diagnostics.ProcessStartInfo
            {
                FileName = runasPath,
                Arguments = "/trustlevel:0x20000 " + quotedExe,
                UseShellExecute = false,
                CreateNoWindow = true,
                WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden,
            };
            // Mark the env so the demoted child knows it's the relaunch and
            // won't loop. runas + CreateProcess passes the parent env block
            // to the new child by default.
            psi.EnvironmentVariables[RelaunchEnvVar] = "1";
            using var spawned = System.Diagnostics.Process.Start(psi);
            if (spawned is null)
            {
                StartupTrace.Write("de-elevate: Process.Start returned null");
                return false;
            }
            StartupTrace.Write($"de-elevate: runas spawned as PID {spawned.Id}");
        }
        catch (Exception ex)
        {
            StartupTrace.Write($"de-elevate: spawn THREW: {ex.GetType().Name}: {ex.Message}");
            return false;
        }
        // Spawn succeeded — shut ourselves down so only the medium child remains.
        // Use Shutdown(0) to signal a clean exit (NOT a startup error).
        StartupTrace.Write("de-elevate: calling Shutdown(0) to let runas child take over");
        Shutdown(0);
        return true;
    }

    /// <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);
    }
}