import { defaultLocale, isLocale, localeStorageKey, type Locale } from "./locales";

export function createLocaleStore(storage: () => Pick<Storage, "getItem" | "setItem"> | undefined) {
  let locale: Locale = defaultLocale;
  let restored = false;
  const listeners = new Set<() => void>();
  const emit = () => listeners.forEach((listener) => listener());

  return {
    getSnapshot: () => locale,
    getServerSnapshot: () => defaultLocale,
    subscribe(listener: () => void) {
      listeners.add(listener);
      if (!restored) {
        restored = true;
        try {
          const saved = storage()?.getItem(localeStorageKey);
          if (isLocale(saved)) locale = saved;
        } catch { /* Storage may be disabled by the browser. */ }
        emit();
      }
      return () => { listeners.delete(listener); };
    },
    setLocale(value: Locale) {
      if (!isLocale(value)) return;
      locale = value;
      try { storage()?.setItem(localeStorageKey, value); } catch { /* Keep the session choice when storage is unavailable. */ }
      emit();
    },
  };
}