runtimeMode.ts

/**
 * runtimeMode — detects whether the app is currently running as an
 * installed, standalone PWA (added to home screen / launched in its own
 * window, no browser chrome) vs. a normal browser tab.
 *
 * This is a display-mode check only — the `display-mode: standalone` media
 * query (with the iOS Safari `navigator.standalone` fallback, which doesn't
 * support that query). It's not a fingerprinting signal: it isn't combined
 * with anything else, isn't sent anywhere, and doesn't distinguish one
 * visitor from another — it only distinguishes *how* this page happens to be
 * displayed right now. So it lives outside the Observer.ts §6 detector
 * whitelist rather than in it; see `sessionState.ts` for its one use.
 */

export function isStandalonePwa(): boolean {
  try {
    if (
      typeof window !== 'undefined' &&
      window.matchMedia?.('(display-mode: standalone)').matches
    ) {
      return true;
    }
    // iOS Safari never supported the display-mode media query; it exposes this instead.
    return (
      typeof navigator !== 'undefined' &&
      (navigator as Navigator & { standalone?: boolean }).standalone === true
    );
  } catch {
    // window/navigator/matchMedia unavailable in this environment (e.g. tests).
    return false;
  }
}