// Lightweight User-Agent -> "Browser on OS" summary for account-activity logging.
// No UA-parsing library is installed in this project; this covers the common cases
// (desktop/mobile browsers, major OSes) without pulling one in for a single display string.

function detectBrowser(ua) {
  if (/Edg\//.test(ua)) return 'Edge';
  if (/OPR\//.test(ua) || /Opera/.test(ua)) return 'Opera';
  if (/SamsungBrowser/.test(ua)) return 'Samsung Internet';
  if (/CriOS/.test(ua)) return 'Chrome';
  if (/FxiOS/.test(ua)) return 'Firefox';
  if (/Firefox\//.test(ua)) return 'Firefox';
  if (/Chrome\//.test(ua)) return 'Chrome';
  if (/Safari\//.test(ua) && /Version\//.test(ua)) return 'Safari';
  return null;
}

function detectOS(ua) {
  if (/Windows/.test(ua)) return 'Windows';
  if (/iPhone|iPad|iPod/.test(ua)) return 'iOS';
  if (/Mac OS X/.test(ua)) return 'macOS';
  if (/Android/.test(ua)) return 'Android';
  if (/Linux/.test(ua)) return 'Linux';
  return null;
}

function describeUserAgent(uaString) {
  if (!uaString) return 'Unknown device';
  const browser = detectBrowser(uaString);
  const os = detectOS(uaString);
  if (browser && os) return `${browser} on ${os}`;
  if (browser) return browser;
  if (os) return os;
  return 'Unknown device';
}

module.exports = { describeUserAgent };