feat: craetea LANGUAGES union and useTransltate

Author: ryoppippi

2025/src/i18n/index.ts

@@ -0,0 +1,15 @@
+export const LANGUAGES = ['ja', 'en'] as const;
+
+type Lang = typeof LANGUAGES[number];
+
+export function getLangFromUrl(url: URL): Lang {
+	const [, lang] = url.pathname.replace(import.meta.env.BASE_URL, '').split('/');
+	if (lang in LANGUAGES) {
+		return lang as Lang;
+	}
+	throw new Error(`Invalid language: ${lang}`);
+}
+
+export function useTranslate(lang: Lang): (...translations: string[]) => string {
+	return (...translations: string[]) => translations[LANGUAGES.indexOf(lang)]; ;
+}