const { execSync } = require('child_process');

// Real monitor resolution instead of a hardcoded viewport — this suite runs
// on whatever box the self-hosted runner/dev machine happens to be (varies:
// 1366x768, 1920x1080, ...). Memoized per process.
let _cachedViewport = null;

function detectViewport() {
  if (_cachedViewport) return _cachedViewport;
  const FALLBACK = { width: 1366, height: 768 };
  let detected = null;
  try {
    if (process.platform === 'linux') {
      const out = execSync('xrandr --current 2>/dev/null', { encoding: 'utf8' });
      const m = out.match(/(\d+)x(\d+)\s+[\d.]+\*/);
      if (m) detected = { width: Number(m[1]), height: Number(m[2]) };
    } else if (process.platform === 'win32') {
      const out = execSync(
        'powershell -NoProfile -Command "Add-Type -AssemblyName System.Windows.Forms; ' +
        '$b = [System.Windows.Forms.Screen]::PrimaryScreen.Bounds; Write-Output \\"$($b.Width)x$($b.Height)\\""',
        { encoding: 'utf8', windowsHide: true },
      ).trim();
      const m = out.match(/(\d+)x(\d+)/);
      if (m) detected = { width: Number(m[1]), height: Number(m[2]) };
    } else if (process.platform === 'darwin') {
      const out = execSync('system_profiler SPDisplaysDataType 2>/dev/null', { encoding: 'utf8' });
      const m = out.match(/Resolution:\s*(\d+)\s*x\s*(\d+)/);
      if (m) detected = { width: Number(m[1]), height: Number(m[2]) };
    }
  } catch {
    // No xrandr on a headless CI box, PowerShell blocked, etc. — fall back.
  }
  _cachedViewport = detected ?? FALLBACK;
  return _cachedViewport;
}

module.exports = { detectViewport };