// 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());
// True while the current offline state was entered automatically (no network detected), not chosen
// by the player. An auto offline self-heals to online when the network returns; a deliberate one is
// left as the player's choice.
let auto = $state(false);

/** offlineMode exposes the reactive offline flags; read them in markup / $derived. */
export const offlineMode = {
  /** active is true while the app is in offline mode (deliberate or auto-detected). */
  get active(): boolean {
    return active;
  },
  /** auto is true while offline was entered automatically (no network), not by the player. */
  get auto(): boolean {
    return auto;
  },
};

/**
 * setOfflineMode enters or leaves offline mode. By default it persists the choice (device-scoped) —
 * a deliberate choice (the Settings toggle, or the cold-start "no connection" dialog). Pass
 * persist=false for a transient, auto-detected offline (a cold start with no network interface): the
 * flag holds for the session but is not saved, so the next launch re-evaluates the network.
 */
export function setOfflineMode(on: boolean, persist = true): void {
  active = on;
  auto = on && !persist; // a non-persisted offline is auto-detected; a persisted one is deliberate
  if (persist) saveOfflinePref(on);
}

/** The toggle-flip readiness wait: entering offline waits at most this long for the enabled
 *  variants' dictionaries before reverting to online (the fetch then continues in the background). */
export const TOGGLE_READY_BUDGET_MS = 5000;

/**
 * requestOffline attempts to enter offline mode from the Settings toggle. It fetches the enabled
 * variants' dictionaries cache-first and, if every one is available within the readiness budget,
 * switches to a deliberate (persisted) offline mode and returns true. Otherwise it stays online and
 * returns false — the caller shows the "needs internet" note — while the fetch keeps warming the
 * cache so a later flip is instant. The readiness glue and the dict loader are imported dynamically,
 * so neither is pulled into the main bundle. Returns false with no profile.
 */
export async function requestOffline(prof: Profile | null, budgetMs = TOGGLE_READY_BUDGET_MS): Promise<boolean> {
  if (!prof) return false;
  const m = await import('./dict/offlineready');
  const ready = await m.ensureOfflineDicts(prof, budgetMs);
  if (ready) setOfflineMode(true);
  return ready;
}

// 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;
    });
}