// Pure PWA install helpers, kept out of the Svelte layer (and free of app imports) so the
// platform branching is unit-testable in the node test env. The reactive runtime (the captured
// install prompt, the Mini-App gate, the service-worker registration) lives in pwa.svelte.ts.

/** InstallMode is how the install call-to-action resolves for the current platform. */
export type InstallMode = 'oneTap' | 'iosInstructions' | 'hidden';

/**
 * isStandalone reports whether the app is already running as an installed PWA — launched from
 * the home screen / desktop rather than a browser tab. Both the standard display-mode media
 * query and the iOS-only navigator.standalone flag are checked. Returns false with no window
 * (e.g. under the unit tests).
 */
export function isStandalone(): boolean {
  if (typeof window === 'undefined') return false;
  const displayMode = window.matchMedia?.('(display-mode: standalone)').matches ?? false;
  const iosStandalone =
    (window.navigator as Navigator & { standalone?: boolean }).standalone === true;
  return displayMode || iosStandalone;
}

/**
 * isIosSafari reports whether the app runs in Safari on iOS / iPadOS — the only browser there
 * that can add a site to the home screen, and one with no programmatic install (it never fires
 * beforeinstallprompt). In-app webviews (Telegram, VK) and the iOS Chrome/Firefox/Edge wrappers
 * are excluded, as is desktop Safari. Used to switch the CTA to manual Share -> Add-to-Home-Screen
 * instructions.
 */
export function isIosSafari(): boolean {
  if (typeof navigator === 'undefined') return false;
  const ua = navigator.userAgent;
  // iPadOS 13+ reports a Mac UA but exposes touch points — catch that as iOS too.
  const isIos =
    /iPhone|iPod|iPad/.test(ua) || (/Macintosh/.test(ua) && (navigator.maxTouchPoints ?? 0) > 1);
  if (!isIos) return false;
  // Safari only: the iOS Chrome (CriOS), Firefox (FxiOS), Edge (EdgiOS), Opera (OPiOS) and the
  // Google-app (GSA) wrappers all carry "Safari" but cannot add to the home screen from our CTA.
  return /Safari/.test(ua) && !/CriOS|FxiOS|EdgiOS|OPiOS|GSA/.test(ua);
}

/**
 * resolveInstallMode chooses how the install CTA should behave from the platform facts:
 * `deferredAvailable` — a beforeinstallprompt event was captured (Chromium one-tap); `standalone`
 * — already installed; `iosSafari` — manual instructions apply; `inMiniApp` — running inside a
 * Telegram/VK Mini App. The CTA is offered only on the plain web and never once installed.
 */
export function resolveInstallMode(facts: {
  deferredAvailable: boolean;
  standalone: boolean;
  iosSafari: boolean;
  inMiniApp: boolean;
}): InstallMode {
  if (facts.inMiniApp || facts.standalone) return 'hidden';
  if (facts.deferredAvailable) return 'oneTap';
  if (facts.iosSafari) return 'iosInstructions';
  return 'hidden';
}