nextjs-i18n

# Next.js 16 Internationalization (SOLID)

## Modular Architecture

```text
src/
├── app/[lang]/
│   ├── layout.tsx           # Imports from modules/cores/i18n
│   └── page.tsx
│
├── modules/cores/i18n/       # i18n module in cores
│   ├── src/
│   │   ├── interfaces/
│   │   │   └── i18n.interface.ts
│   │   ├── services/
│   │   │   ├── dictionary.service.ts
│   │   │   └── locale.service.ts
│   │   └── config/
│   │       └── locales.ts
│   └── dictionaries/
│       ├── en.json
│       └── fr.json
│
└── proxy.ts                  # Root level (Next.js requirement)
```

---

## Config (modules/cores/i18n/src/config/locales.ts)

```typescript
/** Supported locales configuration. */
export const locales = ['en', 'fr', 'de'] as const

/** Default locale. */
export const defaultLocale = 'en'

/** Locale type. */
export type Locale = (typeof locales)[number]
```

---

## Interfaces (modules/cores/i18n/src/interfaces/i18n.interface.ts)

```typescript
import type { Locale } from '../config/locales'

/** Dictionary structure. */
export interface Dictionary {
  home: {
    title: string
    description: string
  }
  nav: {
    home: string
    about: string
  }
}

/** Page props with lang param. */
export interface LangPageProps {
  params: Promise<{ lang: Locale }>
}

/** Layout props with lang param. */
export interface LangLayoutProps {
  children: React.ReactNode
  params: Promise<{ lang: Locale }>
}
```

---

## Services (modules/cores/i18n/src/services/)

### dictionary.service.ts

```typescript
import 'server-only'
import type { Locale } from '../config/locales'
import type { Dictionary } from '../interfaces/i18n.interface'

const dictionaries: Record<Locale, () => Promise<Dictionary>> = {
  en: () => import('../../dictionaries/en.json').then((m) => m.default),
  fr: () => import('../../dictionaries/fr.json').then((m) => m.default),
  de: () => import('../../dictionaries/de.json').then((m) => m.default),
}

/**
 * Get dictionary for locale.
 *
 * @param locale - Targ