const koffi = require('koffi');
const user32 = koffi.load('user32.dll');

const SetCursorPos    = user32.func('bool SetCursorPos(int x, int y)');
const mouse_event     = user32.func('void mouse_event(uint32 dwFlags, uint32 dx, uint32 dy, uint32 dwData, uintptr dwExtraInfo)');
const keybd_event     = user32.func('void keybd_event(uint8 bVk, uint8 bScan, uint32 dwFlags, uintptr dwExtraInfo)');
const GetSystemMetrics = user32.func('int GetSystemMetrics(int nIndex)');

const MOUSEEVENTF_LEFTDOWN   = 0x0002;
const MOUSEEVENTF_LEFTUP     = 0x0004;
const MOUSEEVENTF_RIGHTDOWN  = 0x0008;
const MOUSEEVENTF_RIGHTUP    = 0x0010;
const MOUSEEVENTF_MIDDLEDOWN = 0x0020;
const MOUSEEVENTF_MIDDLEUP   = 0x0040;
const MOUSEEVENTF_WHEEL      = 0x0800;
const KEYEVENTF_KEYUP        = 0x0002;

const VK = {
  backspace:0x08, tab:0x09, enter:0x0D, shift:0x10, control:0x11,
  alt:0x12, escape:0x1B, space:0x20, pageup:0x21, pagedown:0x22,
  end:0x23, home:0x24, left:0x25, up:0x26, right:0x27, down:0x28,
  delete:0x2E, insert:0x2D,
  f1:0x70,f2:0x71,f3:0x72,f4:0x73,f5:0x74,f6:0x75,
  f7:0x76,f8:0x77,f9:0x78,f10:0x79,f11:0x7A,f12:0x7B,
};

function toVk(key) {
  if (VK[key]) return VK[key];
  const c = key.toUpperCase().charCodeAt(0);
  return (c >= 0x30 && c <= 0x5A) ? c : 0;
}

function moveMouse(x, y)          { SetCursorPos(x, y); }

function mouseClick(btn) {
  const [dn, up] = btn === 'right'  ? [MOUSEEVENTF_RIGHTDOWN, MOUSEEVENTF_RIGHTUP]
                 : btn === 'middle' ? [MOUSEEVENTF_MIDDLEDOWN, MOUSEEVENTF_MIDDLEUP]
                 :                    [MOUSEEVENTF_LEFTDOWN, MOUSEEVENTF_LEFTUP];
  mouse_event(dn, 0, 0, 0, 0);
  mouse_event(up, 0, 0, 0, 0);
}

function mouseToggle(state, btn) {
  const down = btn === 'right' ? MOUSEEVENTF_RIGHTDOWN : btn === 'middle' ? MOUSEEVENTF_MIDDLEDOWN : MOUSEEVENTF_LEFTDOWN;
  const up   = btn === 'right' ? MOUSEEVENTF_RIGHTUP   : btn === 'middle' ? MOUSEEVENTF_MIDDLEUP   : MOUSEEVENTF_LEFTUP;
  mouse_event(state === 'down' ? down : up, 0, 0, 0, 0);
}

function scrollMouse(dx, dy) {
  if (dy) mouse_event(MOUSEEVENTF_WHEEL, 0, 0, -dy * 120, 0);
}

function keyToggle(key, state) {
  const vk = toVk(key);
  if (vk) keybd_event(vk, 0, state === 'up' ? KEYEVENTF_KEYUP : 0, 0);
}

function getScreenSize() {
  return { width: GetSystemMetrics(0), height: GetSystemMetrics(1) };
}

module.exports = { moveMouse, mouseClick, mouseToggle, scrollMouse, keyToggle, getScreenSize };