feat: add i18n - dict, en\ru, state

web/src/lib/i18n/locale.svelte.ts

@@ -0,0 +1,60 @@
+import { BASE_LOCALE, isLocale, type Dict, type Locale } from './dict';
+import { ru } from './ru';
+import { en } from './en';
+
+const STORAGE_KEY = 'locale';
+
+const DICTS: Record<Locale, Dict> = { ru, en };
+
+let locale = $state<Locale>(BASE_LOCALE);
+
+function storage(): Storage | null {
+	return typeof localStorage === 'undefined' ? null : localStorage;
+}
+
+export function getLocale(): Locale {
+	return locale;
+}
+
+export function getDict(): Dict {
+	return DICTS[locale];
+}
+
+/** Словарь активной локали; для отсутствующих в ней значений — фолбэк на базовую. */
+export function getMergedDict(): Dict {
+	if (locale === BASE_LOCALE) return DICTS[BASE_LOCALE];
+	const active = DICTS[locale];
+	const base = DICTS[BASE_LOCALE];
+	return new Proxy(base, {
+		get(_target, section: string) {
+			const a = (active as unknown as Record<string, unknown>)[section];
+			const b = (base as unknown as Record<string, unknown>)[section];
+			if (
+				a && b && typeof a === 'object' && typeof b === 'object'
+			) {
+				return { ...(b as object), ...(a as object) };
+			}
+			return a ?? b;
+		}
+	}) as Dict;
+}
+
+export function setLocale(next: Locale): void {
+	locale = next;
+	storage()?.setItem(STORAGE_KEY, next);
+	syncLangAttr();
+}
+
+/** Читает сохранённый выбор и синхронизирует атрибут lang. Вызывается на клиенте. */
+export function initLocale(): void {
+	if (typeof window === 'undefined') return;
+	const saved = storage()?.getItem(STORAGE_KEY);
+	if (isLocale(saved)) locale = saved;
+	syncLangAttr();
+}
+
+function syncLangAttr(): void {
+	if (typeof document !== 'undefined') {
+		document.documentElement.lang = locale;
+	}
+}