tjdify/web/i18n/server.ts

import 'server-only'

import { cookies, headers } from 'next/headers'
import Negotiator from 'negotiator'
import { match } from '@formatjs/intl-localematcher'
import type { Locale } from '.'
import { i18n } from '.'

export const getLocaleOnServer = (): Locale => {
  // @ts-expect-error locales are readonly
  const locales: string[] = i18n.locales

  let languages: string[] | undefined
  // get locale from cookie
  const localeCookie = cookies().get('locale')
  languages = localeCookie?.value ? [localeCookie.value] : []

  if (!languages.length) {
    // Negotiator expects plain object so we need to transform headers
    const negotiatorHeaders: Record<string, string> = {}
    headers().forEach((value, key) => (negotiatorHeaders[key] = value))
    // Use negotiator and intl-localematcher to get best locale
    languages = new Negotiator({ headers: negotiatorHeaders }).languages()
  }

  // match locale
  const matchedLocale = match(languages, locales, i18n.defaultLocale) as Locale
  return matchedLocale
}

// We enumerate all dictionaries here for better linting and typescript support
// We also get the default import for cleaner types
const dictionaries = {
  'en': () => import('@/dictionaries/en.json').then(module => module.default),
  'zh-Hans': () => import('@/dictionaries/zh-Hans.json').then(module => module.default),
} as { [locale: string]: () => Promise<any> }

export const getDictionary = async (locale: Locale = 'en') => {
  try {
    return await dictionaries[locale]()
  }
  catch (e) { console.error('locale not found', locale) }
}