feat: add i18n entry script

packages/app/src/libs/i18n/index.ts

@@ -0,0 +1,63 @@
+import i18next, { Resource } from 'i18next';
+import {
+    I18nextProvider,
+    initReactI18next,
+    useTranslation,
+} from 'react-i18next';
+import { LOCALES } from './resources';
+import type en_US from './resources/en.json';
+
+// See https://react.i18next.com/latest/typescript
+declare module 'react-i18next' {
+    interface CustomTypeOptions {
+        // custom namespace type if you changed it
+        // defaultNS: 'ns1';
+        // custom resources type
+        resources: {
+            en: typeof en_US;
+        };
+    }
+}
+
+const STORAGE_KEY = 'i18n_lng';
+
+export { i18n, useTranslation, I18nProvider, LOCALES };
+
+const resources = LOCALES.reduce<Resource>(
+    (acc, { tag, res }) => ({ ...acc, [tag]: { translation: res } }),
+    {}
+);
+
+const fallbackLng = LOCALES[0].tag;
+const standardizeLocale = (language: string) => {
+    if (LOCALES.find(locale => locale.tag === language)) return language;
+    if (
+        LOCALES.find(
+            locale => locale.tag === language.slice(0, 2).toLowerCase()
+        )
+    )
+        return language;
+    return fallbackLng;
+};
+
+const language = standardizeLocale(
+    localStorage.getItem(STORAGE_KEY) ?? navigator.language
+);
+
+const i18n = i18next.createInstance();
+i18n.use(initReactI18next).init({
+    lng: language,
+    fallbackLng,
+    debug: process.env['NODE_ENV'] === 'development',
+
+    resources,
+    interpolation: {
+        escapeValue: false, // not needed for react as it escapes by default
+    },
+});
+
+i18n.on('languageChanged', lng => {
+    localStorage.setItem(STORAGE_KEY, lng);
+});
+
+const I18nProvider = I18nextProvider;