using System;
using System.Runtime.InteropServices;
using System.Windows.Input;

namespace Paca.App.Services;

public sealed class GlobalHotkeyService : IDisposable
{
    public const uint MOD_ALT = 0x0001;
    public const uint MOD_CONTROL = 0x0002;
    public const uint MOD_SHIFT = 0x0004;
    public const uint MOD_WIN = 0x0008;
    public const uint MOD_NOREPEAT = 0x4000;
    public const int WM_HOTKEY = 0x0312;

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

    private IntPtr _hWnd;
    private int _currentId;
    private bool _isRegistered;

    public bool IsRegistered => _isRegistered;

    public event Action? HotkeyPressed;

    public bool Register(IntPtr hWnd, int id, string hotkeyStr)
    {
        Unregister();

        if (!TryParseHotkey(hotkeyStr, out uint modifiers, out uint vk))
        {
            return false;
        }

        _hWnd = hWnd;
        _currentId = id;
        _isRegistered = RegisterHotKey(_hWnd, _currentId, modifiers | MOD_NOREPEAT, vk);
        return _isRegistered;
    }

    public void Unregister()
    {
        if (_isRegistered && _hWnd != IntPtr.Zero)
        {
            UnregisterHotKey(_hWnd, _currentId);
            _isRegistered = false;
        }
    }

    public IntPtr HandleWindowMessages(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        if (msg == WM_HOTKEY && wParam.ToInt32() == _currentId)
        {
            HotkeyPressed?.Invoke();
            handled = true;
        }
        return IntPtr.Zero;
    }

    public static bool TryParseHotkey(string? hotkeyStr, out uint fsModifiers, out uint vk)
    {
        fsModifiers = 0;
        vk = 0;

        if (string.IsNullOrWhiteSpace(hotkeyStr)) return false;

        var parts = hotkeyStr.Split('+', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
        if (parts.Length == 0) return false;

        for (int i = 0; i < parts.Length - 1; i++)
        {
            var part = parts[i].ToLowerInvariant();
            if (part is "ctrl" or "control") fsModifiers |= MOD_CONTROL;
            else if (part is "alt") fsModifiers |= MOD_ALT;
            else if (part is "shift") fsModifiers |= MOD_SHIFT;
            else if (part is "win" or "windows") fsModifiers |= MOD_WIN;
            else return false;
        }

        var keyPart = parts[^1].ToUpperInvariant();
        if (keyPart is "SPACE") vk = 0x20;
        else if (keyPart is "RETURN" or "ENTER") vk = 0x0D;
        else if (keyPart is "ESCAPE" or "ESC") vk = 0x1B;
        else if (keyPart.Length == 1 && keyPart[0] >= 'A' && keyPart[0] <= 'Z') vk = (uint)keyPart[0];
        else if (keyPart.Length == 1 && keyPart[0] >= '0' && keyPart[0] <= '9') vk = (uint)keyPart[0];
        else if (keyPart.StartsWith("F") && int.TryParse(keyPart[1..], out int fNum) && fNum >= 1 && fNum <= 24)
        {
            vk = (uint)(0x70 + (fNum - 1)); // VK_F1 = 0x70
        }
        else
        {
            return false;
        }

        return true;
    }

    public void Dispose()
    {
        Unregister();
    }
}