Restore dependency-free i18n foundation

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/package.json

@@ -20,7 +20,6 @@
     "build-storybook": "storybook build -c storybook/.storybook -o storybook-static",
     "preview": "vite preview",
     "typecheck": "tsc -b",
-    "test": "vitest run",
     "clean": "rm -rf dist storybook-static tsconfig.tsbuildinfo",
     "prepack": "rm -f package.dev.json && cp package.json package.dev.json && node ../scripts/generate-ui-package-json.mjs",
     "postpack": "if [ -f package.dev.json ]; then mv package.dev.json package.json; fi"
@@ -53,14 +52,12 @@
     "clsx": "^2.1.1",
     "cmdk": "^1.1.1",
     "hermes-paperclip-adapter": "^0.2.0",
-    "i18next": "^26.1.0",
     "lexical": "0.35.0",
     "lucide-react": "^0.574.0",
     "mermaid": "^11.12.0",
     "radix-ui": "^1.4.3",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
-    "react-i18next": "^17.0.7",
     "react-markdown": "^10.1.0",
     "react-router-dom": "^7.1.5",
     "remark-gfm": "^4.0.1",

ui/src/i18n/index.ts

@@ -1,24 +1,25 @@
-import i18n, { type InitOptions, type TOptions } from "i18next";
-import { initReactI18next, useTranslation as useReactI18nextTranslation } from "react-i18next";
+import { DEFAULT_LOCALE, localeMessages } from "./locales";
 
-import { DEFAULT_LOCALE, i18nextResources, supportedLocales } from "./locales";
-
-const i18nextOptions: InitOptions = {
-  resources: i18nextResources,
-  lng: DEFAULT_LOCALE,
-  fallbackLng: DEFAULT_LOCALE,
-  supportedLngs: supportedLocales,
-  defaultNS: "translation",
-  interpolation: { escapeValue: false },
-  returnObjects: false,
-  initAsync: false,
+type TranslationOptions = {
+  defaultValue?: string;
 };
 
-i18n.use(initReactI18next).init(i18nextOptions);
+function resolveLocaleValue(key: string) {
+  const path = key.split(".");
+  let value: unknown = localeMessages[DEFAULT_LOCALE];
 
-export function t(key: string, options: TOptions = {}) {
-  return i18n.t(key, options);
+  for (const segment of path) {
+    if (!value || typeof value !== "object" || Array.isArray(value)) return null;
+    value = (value as Record<string, unknown>)[segment];
+  }
+
+  return typeof value === "string" ? value : null;
 }
 
-export const useTranslation = useReactI18nextTranslation;
-export { i18n };
+export function t(key: string, options: TranslationOptions = {}) {
+  return resolveLocaleValue(key) ?? options.defaultValue ?? key;
+}
+
+export function useTranslation() {
+  return { t };
+}

ui/src/i18n/locales.ts

@@ -1,7 +1,3 @@
-import type { Resource } from "i18next";
-
-import { assertValidLocaleMessages } from "./locale-validation";
-
 export const DEFAULT_LOCALE = "en" as const;
 
 const localeModules = import.meta.glob("./locales/*.json", {
@@ -23,19 +19,4 @@ if (!(DEFAULT_LOCALE in localeMessages)) {
   throw new Error(`Missing default locale messages for ${DEFAULT_LOCALE}`);
 }
 
-for (const [locale, messages] of Object.entries(localeMessages)) {
-  try {
-    assertValidLocaleMessages(messages);
-  } catch (error) {
-    const message = error instanceof Error ? error.message : String(error);
-    throw new Error(`Invalid ${locale} locale messages: ${message}`);
-  }
-}
-
-export const supportedLocales = Object.keys(localeMessages);
-
-export const i18nextResources: Resource = Object.fromEntries(
-  Object.entries(localeMessages).map(([locale, messages]) => [locale, { translation: messages }]),
-) as Resource;
-
 export type SupportedLocale = keyof typeof localeMessages;