using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Interop;
using System.Windows.Media;
using System.Windows.Threading;

namespace DeskCore;

/// <summary>Eine "Box" auf dem Desktop, die den Inhalt einer Kategorie zeigt.</summary>
public partial class FenceWindow : Window
{
    private const double CollapsedHeight = 38;
    private readonly DispatcherTimer _saveTimer;
    private bool _applying;

    public string Category { get; private set; }

    public FenceWindow(string category)
    {
        InitializeComponent();
        Category = category;
        _saveTimer = new DispatcherTimer(TimeSpan.FromMilliseconds(700), DispatcherPriority.Background, (_, _) =>
        {
            _saveTimer!.Stop();
            AppSettings.Current.Save();
        }, Dispatcher);
        _saveTimer.Stop();

        ApplyBounds();
        LocationChanged += (_, _) => RememberBounds();
        SizeChanged += (_, _) => RememberBounds();
        SourceInitialized += (_, _) => PinToDesktop();
        Refresh();
    }

    private CategoryMeta Meta => AppSettings.Current.Meta(Category);

    public void Rename(string newName)
    {
        Category = newName;
        Refresh();
    }

    // ---------- Position/Größe ----------

    private void ApplyBounds()
    {
        _applying = true;
        var m = Meta;
        Width = Math.Max(MinWidth, m.FenceW);
        Height = m.FenceCollapsed ? CollapsedHeight : Math.Max(120, m.FenceH);
        var wa = Screens.PrimaryWorkArea;
        double left = m.FenceX ?? wa.Right - Width - 24, top = m.FenceY ?? wa.Top + 24;
        // Bildschirm abgesteckt? → zurück auf den Hauptbildschirm (oben rechts)
        if (!Screens.IsReachable(new Rect(left, top, Width, Height)))
        {
            left = wa.Right - Width - 24;
            top = wa.Top + 24;
            m.FenceX = left;
            m.FenceY = top;
        }
        Left = left;
        Top = top;
        Body.Visibility = m.FenceCollapsed ? Visibility.Collapsed : Visibility.Visible;
        _applying = false;
    }

    /// <summary>Nach Bildschirm-Änderungen: Box wieder sichtbar machen.</summary>
    public void EnsureOnScreen()
    {
        if (Screens.IsReachable(new Rect(Left, Top, ActualWidth, ActualHeight))) return;
        Meta.FenceX = null;
        Meta.FenceY = null;
        ApplyBounds();
        AppSettings.Current.Save();
    }

    private void RememberBounds()
    {
        if (_applying || !IsLoaded) return;
        var m = Meta;
        m.FenceX = Left;
        m.FenceY = Top;
        m.FenceW = Width;
        if (!m.FenceCollapsed) m.FenceH = Height;
        _saveTimer.Stop();
        _saveTimer.Start();
    }

    private void ToggleCollapsed()
    {
        Meta.FenceCollapsed = !Meta.FenceCollapsed;
        ApplyBounds();
        AppSettings.Current.Save();
    }

    // ---------- Inhalt ----------

    public void Refresh()
    {
        var meta = Meta;
        TitleText.Text = Category;
        GlyphText.Text = meta.Glyph ?? "";
        GlyphText.Foreground = CategoryColors.Brush(meta.Color) ?? (Brush)FindResource("TextBrush");

        var items = Storage.Entries(Storage.CategoryPath(Category))
            .Select(p => new IconItem { Path = p })
            .OrderBy(i => !Directory.Exists(i.Path)).ThenBy(i => i.Name, StringComparer.CurrentCultureIgnoreCase)
            .ToList();
        int px = (int)Math.Round(32 * VisualTreeHelper.GetDpi(this).DpiScaleX);
        foreach (var i in items) IconLoader.Load(i, px);
        Items.ItemsSource = items;
        CountText.Text = items.Count.ToString();
        EmptyText.Visibility = items.Count == 0 ? Visibility.Visible : Visibility.Collapsed;
    }

    private List<IconItem> Selected => Items.SelectedItems.Cast<IconItem>().ToList();

    private static void Open(string path)
    {
        try { Process.Start(new ProcessStartInfo(path) { UseShellExecute = true }); }
        catch { }
    }

    private void Items_MouseDoubleClick(object sender, MouseButtonEventArgs e)
    {
        if (MainWindow.FindParent<ListBoxItem>(e.OriginalSource as DependencyObject)?.DataContext is IconItem i) Open(i.Path);
    }

    private void Items_KeyDown(object sender, KeyEventArgs e)
    {
        var sel = Selected;
        if (sel.Count == 0 || App.Win is not { } win) return;
        switch (e.Key)
        {
            case Key.Enter: sel.ForEach(i => Open(i.Path)); e.Handled = true; break;
            case Key.Delete: win.DeleteIcons(sel); e.Handled = true; break;
            case Key.F2 when sel.Count == 1: win.RenameIcon(sel[0]); e.Handled = true; break;
        }
    }

    private void Items_ContextMenuOpening(object sender, ContextMenuEventArgs e)
    {
        var sel = Selected;
        if (sel.Count == 0 || App.Win is not { } win) { e.Handled = true; return; }
        ItemMenu.Items.Clear();
        ItemMenu.Items.Add(MainWindow.MenuItem("Öffnen", "\uE8A7", () => sel.ForEach(i => Open(i.Path)), bold: true, gesture: "Enter"));
        if (sel.Count == 1)
        {
            ItemMenu.Items.Add(MainWindow.MenuItem("Dateispeicherort öffnen", "\uED25", () =>
                Process.Start("explorer.exe", $"/select,\"{sel[0].Path}\"")));
            ItemMenu.Items.Add(MainWindow.MenuItem("Umbenennen", "\uE70F", () => win.RenameIcon(sel[0]), gesture: "F2"));
        }
        ItemMenu.Items.Add(new Separator());

        var moveTo = MainWindow.MenuItem("Verschieben nach", "\uE8DE", null);
        foreach (var c in Storage.Categories().Where(c => !string.Equals(c, Category, StringComparison.OrdinalIgnoreCase)))
            moveTo.Items.Add(MainWindow.MenuItem(c, AppSettings.Current.Categories.GetValueOrDefault(c)?.Glyph ?? "\uF12B",
                () => win.TransferAll(sel.Select(i => i.Path), Storage.CategoryPath(c))));
        if (moveTo.Items.Count > 0) ItemMenu.Items.Add(moveTo);
        ItemMenu.Items.Add(MainWindow.MenuItem("Zurück auf den Desktop legen", "\uE7F4",
            () => win.TransferAll(sel.Select(i => i.Path), Storage.UserDesktop)));
        ItemMenu.Items.Add(MainWindow.MenuItem("Löschen", "\uE74D", () => win.DeleteIcons(sel), gesture: "Entf"));
        ItemMenu.Items.Add(new Separator());
        ItemMenu.Items.Add(MainWindow.MenuItem("In DeskCore zeigen", "\uE8A7", ShowInApp));
    }

    private void MenuButton_Click(object sender, RoutedEventArgs e)
    {
        FenceMenu.Items.Clear();
        FenceMenu.Items.Add(MainWindow.MenuItem("In DeskCore öffnen", "", ShowInApp));
        FenceMenu.Items.Add(MainWindow.MenuItem(Meta.FenceCollapsed ? "Ausklappen" : "Einklappen",
            Meta.FenceCollapsed ? "" : "", ToggleCollapsed));
        FenceMenu.Items.Add(new Separator());
        FenceMenu.Items.Add(MainWindow.MenuItem("Box ausblenden", "", () =>
        {
            Meta.Fence = false;
            AppSettings.Current.Save();
            FenceManager.Sync();
        }));
        FenceMenu.PlacementTarget = MenuButton;
        FenceMenu.IsOpen = true;
    }

    private void ShowInApp() => App.Win?.ShowCategory(Category);

    private Point _dragStart;
    private bool _dragging;

    private void Items_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e) => _dragStart = e.GetPosition(null);

    private void Items_PreviewMouseMove(object sender, MouseEventArgs e)
    {
        if (e.LeftButton != MouseButtonState.Pressed || _dragging) return;
        var d = e.GetPosition(null) - _dragStart;
        if (Math.Abs(d.X) < SystemParameters.MinimumHorizontalDragDistance &&
            Math.Abs(d.Y) < SystemParameters.MinimumVerticalDragDistance) return;
        if (MainWindow.FindParent<ListBoxItem>(e.OriginalSource as DependencyObject) is null) return;
        var paths = Selected.Select(i => i.Path).ToArray();
        if (paths.Length == 0) return;
        _dragging = true;
        try
        {
            // nur "Kopieren" erlauben: der Explorer soll die Datei nicht aus der Kategorie entfernen.
            // In eine andere Box/Kategorie gezogen, verschiebt DeskCore selbst.
            DragDrop.DoDragDrop(Items, new DataObject(DataFormats.FileDrop, paths), DragDropEffects.Copy);
        }
        finally { _dragging = false; }
    }

    private void Items_DragOver(object sender, DragEventArgs e)
    {
        e.Effects = e.Data.GetDataPresent(DataFormats.FileDrop) && !_dragging
            ? (e.AllowedEffects.HasFlag(DragDropEffects.Copy) ? DragDropEffects.Copy : DragDropEffects.Move)
            : DragDropEffects.None;
        e.Handled = true;
    }

    private void Items_Drop(object sender, DragEventArgs e)
    {
        if (!_dragging && e.Data.GetData(DataFormats.FileDrop) is string[] files)
            App.Win?.TransferAll(files, Storage.CategoryPath(Category));
    }

    // ---------- Auf dem Desktop festhalten ----------

    private void PinToDesktop()
    {
        var hwnd = new WindowInteropHelper(this).Handle;
        // Besitzer = Desktop (Progman): bleibt bei Win+D sichtbar und liegt über den Desktop-Icons
        var progman = FindWindow("Progman", null);
        if (progman != IntPtr.Zero) SetWindowLongPtr(hwnd, GWLP_HWNDPARENT, progman);
        // Nicht in Alt+Tab
        var ex = GetWindowLongPtr(hwnd, GWL_EXSTYLE).ToInt64();
        SetWindowLongPtr(hwnd, GWL_EXSTYLE, new IntPtr((ex | WS_EX_TOOLWINDOW) & ~WS_EX_APPWINDOW));
        HwndSource.FromHwnd(hwnd).AddHook(Hook);
        SetWindowPos(hwnd, HWND_BOTTOM, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
    }

    private IntPtr Hook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        switch (msg)
        {
            case WM_WINDOWPOSCHANGING:
                // immer ganz unten bleiben, nie über anderen Fenstern
                var wp = Marshal.PtrToStructure<WINDOWPOS>(lParam);
                wp.hwndInsertAfter = HWND_BOTTOM;
                wp.flags &= ~SWP_NOZORDER;
                Marshal.StructureToPtr(wp, lParam, false);
                break;
            case WM_NCLBUTTONDBLCLK:
                ToggleCollapsed();
                handled = true;
                break;
            case WM_SYSCOMMAND when (wParam.ToInt32() & 0xFFF0) == SC_MAXIMIZE:
                handled = true;
                break;
        }
        return IntPtr.Zero;
    }

    private const int GWL_EXSTYLE = -20, GWLP_HWNDPARENT = -8;
    private const long WS_EX_TOOLWINDOW = 0x80, WS_EX_APPWINDOW = 0x40000;
    private const int WM_WINDOWPOSCHANGING = 0x46, WM_NCLBUTTONDBLCLK = 0xA3, WM_SYSCOMMAND = 0x112, SC_MAXIMIZE = 0xF030;
    private const uint SWP_NOSIZE = 0x1, SWP_NOMOVE = 0x2, SWP_NOZORDER = 0x4, SWP_NOACTIVATE = 0x10;
    private static readonly IntPtr HWND_BOTTOM = new(1);

    [StructLayout(LayoutKind.Sequential)]
    private struct WINDOWPOS
    {
        public IntPtr hwnd, hwndInsertAfter;
        public int x, y, cx, cy;
        public uint flags;
    }

    [DllImport("user32.dll", CharSet = CharSet.Unicode)] private static extern IntPtr FindWindow(string? cls, string? title);
    [DllImport("user32.dll")] private static extern IntPtr GetWindowLongPtr(IntPtr h, int i);
    [DllImport("user32.dll")] private static extern IntPtr SetWindowLongPtr(IntPtr h, int i, IntPtr v);
    [DllImport("user32.dll")] private static extern bool SetWindowPos(IntPtr h, IntPtr after, int x, int y, int cx, int cy, uint flags);
}

/// <summary>Hält die Desktop-Boxen passend zu den Einstellungen.</summary>
public static class FenceManager
{
    private static readonly List<FenceWindow> _open = [];

    public static void Sync()
    {
        var s = AppSettings.Current;
        var wanted = s.FencesEnabled
            ? Storage.Categories().Where(c => s.Categories.GetValueOrDefault(c)?.Fence == true).ToList()
            : [];

        foreach (var f in _open.Where(f => !wanted.Contains(f.Category, StringComparer.OrdinalIgnoreCase)).ToList())
        {
            f.Close();
            _open.Remove(f);
        }

        var wa = SystemParameters.WorkArea;
        foreach (var c in wanted)
        {
            var f = _open.FirstOrDefault(x => string.Equals(x.Category, c, StringComparison.OrdinalIgnoreCase));
            if (f is not null) { f.Refresh(); continue; }

            // Neue Box: neben die vorhandenen setzen
            var meta = s.Meta(c);
            if (meta.FenceX is null)
            {
                // oben rechts beginnen – links liegen meist die Desktop-Icons
                int perRow = Math.Max(1, (int)((wa.Width - 48) / (meta.FenceW + 16)));
                int i = _open.Count;
                meta.FenceX = wa.Right - 24 - meta.FenceW - (i % perRow) * (meta.FenceW + 16);
                meta.FenceY = wa.Top + 24 + (i / perRow) * (meta.FenceH + 16);
            }
            f = new FenceWindow(c);
            _open.Add(f);
            f.Show();
        }
    }

    public static void RefreshAll()
    {
        foreach (var f in _open) f.Refresh();
    }

    public static void EnsureOnScreen()
    {
        foreach (var f in _open) f.EnsureOnScreen();
    }

    public static void Renamed(string oldName, string newName)
    {
        _open.FirstOrDefault(x => string.Equals(x.Category, oldName, StringComparison.OrdinalIgnoreCase))?.Rename(newName);
    }

    public static void CloseAll()
    {
        foreach (var f in _open) f.Close();
        _open.Clear();
    }
}