using System.Runtime.InteropServices;
using System.Windows.Input;
using System.Windows.Interop;
using Microsoft.Win32;

namespace DeskCore;

/// <summary>Systemweites Tastenkürzel (RegisterHotKey).</summary>
public sealed class Hotkey : IDisposable
{
    public const int ModAlt = 0x1, ModCtrl = 0x2, ModShift = 0x4, ModWin = 0x8;
    private const int ModNoRepeat = 0x4000, WmHotkey = 0x0312, Id = 0xB001;

    private readonly IntPtr _hwnd;
    private readonly HwndSource _source;
    private bool _registered;

    public event Action? Pressed;

    public Hotkey(IntPtr hwnd)
    {
        _hwnd = hwnd;
        _source = HwndSource.FromHwnd(hwnd);
        _source.AddHook(Hook);
    }

    /// <summary>Registriert das Kürzel. false = schon von einem anderen Programm belegt.</summary>
    public bool Register(int modifiers, int vk)
    {
        Unregister();
        if (vk == 0) return false;
        _registered = RegisterHotKey(_hwnd, Id, modifiers | ModNoRepeat, vk);
        return _registered;
    }

    public void Unregister()
    {
        if (_registered) UnregisterHotKey(_hwnd, Id);
        _registered = false;
    }

    private IntPtr Hook(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        if (msg == WmHotkey && wParam.ToInt32() == Id)
        {
            Pressed?.Invoke();
            handled = true;
        }
        return IntPtr.Zero;
    }

    public static string Describe(int modifiers, int vk)
    {
        if (vk == 0) return "–";
        var parts = new List<string>();
        if ((modifiers & ModWin) != 0) parts.Add("Win");
        if ((modifiers & ModCtrl) != 0) parts.Add("Strg");
        if ((modifiers & ModAlt) != 0) parts.Add("Alt");
        if ((modifiers & ModShift) != 0) parts.Add("Umschalt");
        var key = KeyInterop.KeyFromVirtualKey(vk);
        parts.Add(key switch
        {
            >= Key.D0 and <= Key.D9 => ((char)('0' + (key - Key.D0))).ToString(),
            Key.Space => "Leertaste",
            _ => key.ToString(),
        });
        return string.Join(" + ", parts);
    }

    public void Dispose()
    {
        Unregister();
        _source.RemoveHook(Hook);
    }

    [DllImport("user32.dll")] private static extern bool RegisterHotKey(IntPtr hWnd, int id, int fsModifiers, int vk);
    [DllImport("user32.dll")] private static extern bool UnregisterHotKey(IntPtr hWnd, int id);
}

/// <summary>Start mit Windows über HKCU\...\Run.</summary>
public static class Autostart
{
    private const string Key = @"Software\Microsoft\Windows\CurrentVersion\Run";
    private const string Name = "DeskCore";
    // Frühere Namen dieser App. "DeskHub" heißt auch ein anderes Programm → nur übernehmen, wenn der Eintrag eindeutig von uns ist.
    private static readonly string[] OldNames = ["DesktopSortierer", "DeskHub"];

    public static bool Enabled
    {
        get
        {
            try
            {
                using var k = Registry.CurrentUser.OpenSubKey(Key);
                return k?.GetValue(Name) is string;
            }
            catch { return false; }
        }
        set
        {
            try
            {
                using var k = Registry.CurrentUser.OpenSubKey(Key, writable: true) ?? Registry.CurrentUser.CreateSubKey(Key);
                if (value) k.SetValue(Name, $"\"{Environment.ProcessPath}\" --minimized");
                else k.DeleteValue(Name, throwOnMissingValue: false);
            }
            catch { }
        }
    }

    /// <summary>Alten Autostart-Eintrag ("DesktopSortierer") auf den neuen Namen umstellen.</summary>
    public static void Migrate()
    {
        try
        {
            using var k = Registry.CurrentUser.OpenSubKey(Key, writable: true);
            if (k is null) return;
            bool wasEnabled = false;
            foreach (var old in OldNames)
            {
                if (k.GetValue(old) is not string cmd) continue;
                bool ours = old == "DesktopSortierer" ||
                            (cmd.Contains($"{old}.exe", StringComparison.OrdinalIgnoreCase) && cmd.Contains("--minimized"));
                if (!ours) continue;
                k.DeleteValue(old, throwOnMissingValue: false);
                wasEnabled = true;
            }
            if (wasEnabled) Enabled = true;
        }
        catch { }
    }

    /// <summary>Falls die exe verschoben wurde: Pfad im Autostart aktualisieren.</summary>
    public static void RefreshPath()
    {
        if (Enabled) Enabled = true;
    }
}