using System.Runtime.InteropServices;

namespace DNFLoadout;

internal sealed class HotkeyManager : IDisposable
{
    private const int AltBit = 0x1;
    private const int CtrlBit = 0x2;
    private const int ShiftBit = 0x4;
    private readonly System.Windows.Forms.Timer _timer = new() { Interval = 50 };
    private readonly HashSet<int> _down = new();
    private Config _config;

    public event Action<Scheme>? Triggered;

    public HotkeyManager(Config config)
    {
        _config = config;
        _timer.Tick += (_, _) => Poll();
        _timer.Start();
    }

    public void UpdateConfig(Config config) => _config = config;

    private static bool Down(int vk) => (GetAsyncKeyState(vk) & 0x8000) != 0;
    private static bool ModCtrl => Down((int)Keys.ControlKey);
    private static bool ModAlt => Down((int)Keys.Menu);
    private static bool ModShift => Down((int)Keys.ShiftKey);

    private void Poll()
    {
        foreach (var scheme in _config.CurrentPage.Schemes)
        {
            if (scheme.KeyCode == 0) continue;
            bool mods = ((scheme.Modifiers & CtrlBit) == 0 || ModCtrl)
                && ((scheme.Modifiers & AltBit) == 0 || ModAlt)
                && ((scheme.Modifiers & ShiftBit) == 0 || ModShift);
            // Reject extra modifiers so Ctrl+F1 cannot fire plain F1.
            if ((scheme.Modifiers & CtrlBit) == 0 && ModCtrl) mods = false;
            if ((scheme.Modifiers & AltBit) == 0 && ModAlt) mods = false;
            if ((scheme.Modifiers & ShiftBit) == 0 && ModShift) mods = false;
            bool key = Down(scheme.KeyCode);
            int id = scheme.KeyCode | (scheme.Modifiers << 16);
            bool was = _down.Contains(id);
            if (key && mods && !was)
            {
                _down.Add(id);
                Triggered?.Invoke(scheme);
            }
            else if (!key || !mods)
            {
                _down.Remove(id);
            }
        }
    }

    public static (int Modifiers, int KeyCode) Capture(Keys keyData)
    {
        var modifiers = 0;
        if ((keyData & Keys.Control) != 0) modifiers |= CtrlBit;
        if ((keyData & Keys.Alt) != 0) modifiers |= AltBit;
        if ((keyData & Keys.Shift) != 0) modifiers |= ShiftBit;
        var keyCode = (int)(keyData & Keys.KeyCode);
        if (keyCode is (int)Keys.ControlKey or (int)Keys.Menu or (int)Keys.ShiftKey
            or (int)Keys.LControlKey or (int)Keys.RControlKey
            or (int)Keys.LMenu or (int)Keys.RMenu
            or (int)Keys.LShiftKey or (int)Keys.RShiftKey)
            return (modifiers, 0);
        return (modifiers, keyCode);
    }

    public void Dispose()
    {
        _timer.Stop();
        _timer.Dispose();
    }

    [DllImport("user32.dll")]
    private static extern short GetAsyncKeyState(int vKey);
}