Internationalization

Internationalization (i18n)

NextCalc Pro supports 8 languages via next-intl with the Next.js App Router.

Supported Locales

Code	Language	Status
en	English	Complete (1278 keys, source of truth)
ru	Russian	Mostly complete (1224 keys)
es	Spanish	Mostly complete (1224 keys)
uk	Ukrainian	Mostly complete (1224 keys)
de	German	Mostly complete (1224 keys)
fr	French	Mostly complete (1275 keys)
ja	Japanese	Mostly complete (1275 keys)
zh	Chinese (Simplified)	Mostly complete (1275 keys)

Non-English locales retain some English fallbacks: fr/ja/zh hold 1275 keys and de/es/ru/uk hold 1224 keys, versus 1278 in en.

File Structure

apps/web/messages/
  en.json    # English (source of truth)
  ru.json
  es.json
  uk.json
  de.json
  fr.json
  ja.json
  zh.json

How It Works

Routing

All pages are under app/[locale]/, so URLs look like:

• /en/plot -- English plot page
• /ru/matrix -- Russian matrix page
• /ja/algorithms -- Japanese algorithms page

Proxy

apps/web/proxy.ts (Next.js 16 renamed middleware to proxy) detects the user's preferred locale and redirects accordingly.

Using Translations

import { useTranslations } from 'next-intl';

export default function MyPage() {
  const t = useTranslations('myNamespace');
  return <h1>{t('title')}</h1>;
}

Translation Key Structure

Keys are nested by namespace:

{
  "calc": {
    "title": "Scientific Calculator",
    "history": "History",
    "clear": "Clear"
  },
  "plots": {
    "title": "Function Plotter",
    "xAxis": "X Axis",
    "yAxis": "Y Axis"
  }
}

Adding a New Language

1. Create apps/web/messages/{code}.json (copy structure from en.json)
2. Translate all 1278 keys
3. Add the locale code to apps/web/i18n/routing.ts (locales are defined via defineRouting)
4. Register the locale in the messageImports map in apps/web/i18n/request.ts (e.g. {code}: () => import('../messages/{code}.json')) -- otherwise its messages won't load
5. Test: pnpm dev and navigate to /{code}/

Key Namespaces

A sample of the ~34 namespaces in en.json:

Namespace	Keys	Description
common	50	Shared UI labels (Submit, Cancel, etc.)
nav	57	Navigation links
calc	56	Calculator UI
plots	41	Plotting interface
algorithms	130	Algorithm pages
settings	70	Settings page
auth	30	Authentication UI
forum	63	Forum interface