using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Interop;
using System.Windows.Media;

namespace DeskCore;

/// <summary>
/// Auswahl nach dem Aufziehen einer Box: Welche Kategorie (oder welcher Ordner) soll hinein?
/// Ein eigenes Fenster statt eines Kontextmenüs – ein Menü ohne aktives Fenster schließt sich sonst gelegentlich von selbst.
/// </summary>
public sealed class BoxPicker : Window
{
    private static BoxPicker? _open;
    private readonly long _shownAt = Environment.TickCount64;
    private bool _done;

    private static AppSettings S => AppSettings.Current;

    /// <param name="area">Fläche der neuen Box in WPF-Einheiten.</param>
    /// <param name="create">Legt die Box mit dem gewählten Tab an.</param>
    public static void Show(Rect area, Action<FenceTab> create)
    {
        _open?.Finish(null);
        _open = new BoxPicker(area, create);
        _open.Show();
    }

    private readonly Action<FenceTab> _create;

    private BoxPicker(Rect area, Action<FenceTab> create)
    {
        _create = create;
        WindowStyle = WindowStyle.None;
        AllowsTransparency = true;
        Background = Brushes.Transparent;
        ResizeMode = ResizeMode.NoResize;
        ShowInTaskbar = false;
        Topmost = true;
        SizeToContent = SizeToContent.WidthAndHeight;
        Title = "Neue Box";

        var res = Application.Current.Resources;
        var list = new StackPanel();

        list.Children.Add(new TextBlock
        {
            Text = "Neue Box hier", FontSize = 14, FontWeight = FontWeights.SemiBold, Margin = new Thickness(12, 8, 12, 0),
            Foreground = (Brush)res["TextBrush"],
        });
        list.Children.Add(new TextBlock
        {
            Text = "Was soll hinein?", FontSize = 12, Margin = new Thickness(12, 2, 12, 6),
            Foreground = (Brush)res["TextSecondaryBrush"],
        });

        var cats = Storage.Categories();
        var catPanel = new StackPanel();
        foreach (var c in cats)
        {
            var meta = S.Categories.GetValueOrDefault(c);
            // Pro Seite steht eine Kategorie nur in einer Box – andere Seiten behalten ihre
            string? hint = S.HasFence(c) ? "wird aus ihrer Box auf dieser Seite hierher geholt" : null;
            catPanel.Children.Add(Row(meta?.Glyph ?? "", CategoryColors.Brush(meta?.Color), c, hint,
                () => Pick(new FenceTab { Value = c })));
        }
        if (cats.Count > 0)
        {
            list.Children.Add(new ScrollViewer
            {
                Content = catPanel, MaxHeight = 360, VerticalScrollBarVisibility = ScrollBarVisibility.Auto,
            });
            list.Children.Add(Divider());
        }
        list.Children.Add(Row("", null, "Zuletzt benutzt", "zeigt, was du zuletzt gestartet hast",
            () => Pick(new FenceTab { Kind = FenceTab.RecentKind })));
        list.Children.Add(Row("", null, "Neue Kategorie …", null, () => PickLater(() =>
            App.Win?.CreateCategoryInteractive() is { } name ? new FenceTab { Value = name } : null)));
        list.Children.Add(Row("", null, "Ordner-Portal …", null, () => PickLater(() =>
            FenceManager.PickFolder() is { } folder ? new FenceTab { Kind = FenceTab.FolderKind, Value = folder } : null)));
        list.Children.Add(Divider());
        list.Children.Add(Row("", null, "Abbrechen", null, () => Finish(null)));

        Content = new Border
        {
            Margin = new Thickness(14), Padding = new Thickness(4), MinWidth = 240, CornerRadius = new CornerRadius(8),
            Background = (Brush)res["FlyoutBrush"], BorderBrush = (Brush)res["FlyoutStrokeBrush"], BorderThickness = new Thickness(1),
            Effect = (System.Windows.Media.Effects.Effect)res["FlyoutShadow"],
            Child = list,
        };

        // Neben dem Mauszeiger öffnen, aber immer ganz auf dem Bildschirm
        Loaded += (_, _) =>
        {
            var mouse = GetCursorPos(out var p) ? new Point(p.X / Screens.Scale, p.Y / Screens.Scale) : area.BottomRight;
            var wa = Screens.WorkAreaAt(mouse);
            Left = Math.Clamp(mouse.X - 14, wa.Left, Math.Max(wa.Left, wa.Right - ActualWidth));
            Top = Math.Clamp(mouse.Y - 14, wa.Top, Math.Max(wa.Top, wa.Bottom - ActualHeight));
            BringToFront();
        };
        KeyDown += (_, e) => { if (e.Key == Key.Escape) Finish(null); };
        // Klick daneben schließt – aber nicht durch ein kurzes Flackern direkt nach dem Öffnen
        Deactivated += (_, _) =>
        {
            if (_done) return;
            if (Environment.TickCount64 - _shownAt < 400) BringToFront();
            else Finish(null);
        };
        Closed += (_, _) => { if (_open == this) _open = null; DrawBoxOverlay.Hide(); };
    }

    private Button Row(string glyph, Brush? glyphBrush, string text, string? hint, Action click)
    {
        var res = Application.Current.Resources;
        var content = new DockPanel();
        var icon = new TextBlock
        {
            Text = glyph, FontFamily = (FontFamily)res["IconFont"], FontSize = 15, Width = 20, Margin = new Thickness(0, 0, 12, 0),
            VerticalAlignment = VerticalAlignment.Center, Foreground = glyphBrush ?? (Brush)res["TextBrush"],
        };
        DockPanel.SetDock(icon, Dock.Left);
        content.Children.Add(icon);
        var texts = new StackPanel { VerticalAlignment = VerticalAlignment.Center };
        texts.Children.Add(new TextBlock { Text = text, Foreground = (Brush)res["TextBrush"] });
        if (hint is not null)
            texts.Children.Add(new TextBlock { Text = hint, FontSize = 11, Foreground = (Brush)res["TextTertiaryBrush"] });
        content.Children.Add(texts);

        var b = new Button
        {
            Style = (Style)res["SubtleButton"], Content = content, HorizontalContentAlignment = HorizontalAlignment.Stretch,
            Padding = new Thickness(10, 7, 10, 7), Focusable = true,
        };
        b.Click += (_, _) => click();
        return b;
    }

    private static Border Divider() => new()
    {
        Height = 1, Margin = new Thickness(4, 4, 4, 4), Background = (Brush)Application.Current.Resources["ControlStrokeBrush"],
    };

    private void Pick(FenceTab tab) => Finish(tab);

    /// <summary>Für Auswahlen mit eigenem Dialog: erst die Auswahl schließen, Rahmen aber stehen lassen.</summary>
    private void PickLater(Func<FenceTab?> ask)
    {
        _done = true;
        Hide();
        var tab = ask();
        if (tab is not null) _create(tab);
        Close();
    }

    private void Finish(FenceTab? tab)
    {
        if (_done) return;
        _done = true;
        Close();
        if (tab is not null) _create(tab);
    }

    /// <summary>
    /// DeskCore läuft im Hintergrund – Windows lässt es nicht ohne Weiteres nach vorne. Ein kurzer Alt-Tastendruck
    /// gibt die Erlaubnis (bewährter Weg, der auch von Windows selbst so akzeptiert wird).
    /// </summary>
    private void BringToFront()
    {
        var hwnd = new WindowInteropHelper(this).Handle;
        if (GetForegroundWindow() != hwnd)
        {
            // Loslassen erst nach dem Wechsel – so landet es bei uns und öffnet nirgends ein Menü
            keybd_event(VK_MENU, 0, 0, UIntPtr.Zero);
            SetForegroundWindow(hwnd);
            keybd_event(VK_MENU, 0, KEYEVENTF_KEYUP, UIntPtr.Zero);
        }
        Activate();
        Focus();
    }

    private const byte VK_MENU = 0x12;
    private const uint KEYEVENTF_KEYUP = 0x2;
    [StructLayout(LayoutKind.Sequential)] private struct POINT { public int X, Y; }
    [DllImport("user32.dll")] private static extern bool GetCursorPos(out POINT p);
    [DllImport("user32.dll")] private static extern IntPtr GetForegroundWindow();
    [DllImport("user32.dll")] private static extern bool SetForegroundWindow(IntPtr hwnd);
    [DllImport("user32.dll")] private static extern void keybd_event(byte vk, byte scan, uint flags, UIntPtr extra);
}