scrabble-game/ui/src/lib/offline.svelte.ts

// The deliberate offline MODE: a sticky, device-scoped reactive flag the app reads to gate the
// network, tint the chrome blue and show only local games. It is the player's own choice (the
// Settings toggle is the source of truth), distinct from connection.svelte.ts's transient
// gateway-reachability signal. The pure persistence + readiness logic lives in offline.ts.

import { loadOfflinePref, saveOfflinePref, offlinePreloadEligible } from './offline';
import { isStandalone } from './pwa';
import { insideTelegram } from './telegram';
import { insideVK } from './vk';
import type { Profile } from './model';

// Not named `state` (a svelte-check hazard: `$state` would then read as a store subscription).
let active = $state(loadOfflinePref());

/** offlineMode exposes the reactive deliberate-offline flag; read it in markup / $derived. */
export const offlineMode = {
  /** active is true while the app is in deliberate offline mode. */
  get active(): boolean {
    return active;
  },
};

/** setOfflineMode enters or leaves offline mode and persists the choice (device-scoped). */
export function setOfflineMode(on: boolean): void {
  active = on;
  saveOfflinePref(on);
}

// The dict-preload warning: true when a first-lobby background preload could not fetch every
// enabled variant's dictionary (typically a poor connection), so offline mode may be incomplete.
// The lobby shows a notice in place of the ad banner while it holds.
let preloadWarn = $state(false);

/** dictPreloadWarning exposes the reactive preload-failure flag; read it in markup / $derived. */
export const dictPreloadWarning = {
  /** active is true while a first-lobby dictionary preload has left a variant unavailable. */
  get active(): boolean {
    return preloadWarn;
  },
};

/** setDictPreloadWarning raises or clears the in-lobby preload-failure notice. */
export function setDictPreloadWarning(on: boolean): void {
  preloadWarn = on;
}

// A preload runs at most once at a time; it finishes before a fresh trigger (a repeated lobby
// mount or a variant-preference change) can start another. Module-scoped so mounts do not stack.
let preloadInFlight = false;

/**
 * kickDictPreload starts a background preload of the enabled variants' dictionaries for an
 * offline-capable install (a standalone web PWA with a confirmed email) while online, so a later
 * switch to offline mode already has the data. It is a no-op in a Telegram/VK mini-app, in a plain
 * browser tab, without a confirmed email, while offline, or when a preload is already running;
 * getDawg's caching makes a repeat run cheap. When warnOnFail is set (the first lobby entry), a
 * fetch failure raises the in-lobby notice, and a later successful run clears it. The dict loader
 * and generator are imported dynamically, so neither is pulled into the main bundle.
 */
export function kickDictPreload(prof: Profile | null, warnOnFail = false): void {
  if (preloadInFlight || !prof) return;
  const eligible = offlinePreloadEligible({
    hasEmail: !!prof.email,
    standalone: isStandalone(),
    inTelegram: insideTelegram(),
    inVK: insideVK(),
    online: typeof navigator === 'undefined' || navigator.onLine !== false,
  });
  if (!eligible) return;
  preloadInFlight = true;
  void import('./dict/preloadrun')
    .then((m) => m.runPreload(prof, warnOnFail))
    .catch(() => {
      /* best-effort warmup — a failed dynamic import just leaves offline data unprimed */
    })
    .finally(() => {
      preloadInFlight = false;
    });
}