i18n.js

const i18n = require('i18next')
const XHR = require('i18next-xhr-backend')
const LanguageDetector = require('i18next-browser-languagedetector')

const detectionOptions = {
  // order and from where user language should be detected
  order: ['querystring', 'cookie', 'localStorage', 'navigator', 'htmlTag'],

  // keys or params to lookup language from
  lookupQuerystring: 'lng',
  lookupCookie: 'lng', //'i18next',
  lookupLocalStorage: 'lng', //'i18nextLng',

  // cache user language on
  // caches: ['localStorage', 'cookie'],
  // excludeCacheFor: ['cimode'], // languages to not persist (cookie, localStorage)

  // optional expire and domain for set cookie
  // cookieMinutes: 10,
  // cookieDomain: 'myDomain',

  // optional htmlTag with lang attribute, the default is:
  // htmlTag: document.documentElement
};

const options = {
  fallbackLng: 'en',
  // given 'en-US': 'all' --> ['en-US', 'en', 'dev'], 'currentOnly' --> 'en-US', 'languageOnly' --> 'en'
  load: 'languageOnly', // no region specific locals like en-US, de-DE (only en, de)
  whitelist: ['en','de'],
  nonExplicitWhitelist: false, // if true will pass eg. en-US if finding en in whitelist

  // have a common namespace used around the full app
  // ns: [ 'common', 'home', 'login', 'signup', 'workout', 'user' ],
  ns: 'common',
  defaultNS: 'common',
  fallbackNS: false,

  debug: true,
  saveMissing: true,

  interpolation: {
    escapeValue: false, // not needed for react!!
    formatSeparator: ',',
    format: (value, format, lng) => {
      if (format === 'uppercase') return value.toUpperCase()
      return value
    }
  },

  detection: detectionOptions,

  // react: {
  //   wait: false,
  //   nsMode: 'default'
  // }
}

// for browser use xhr backend to load translations and browser lng detector
if (process.browser) {
  i18n
    .use(XHR)
    // .use(Cache)
    .use(LanguageDetector)
}

// initialize if not already initialized
if (!i18n.isInitialized) i18n.init(options)

// a simple helper to getInitialProps passed on loaded i18n data
i18n.getInitialProps = (req, namespaces) => {
  if (!namespaces) namespaces = i18n.options.defaultNS
  if (typeof namespaces === 'string') namespaces = [namespaces]

  req.i18n.toJSON = () => null // do not serialize i18next instance and send to client

  const initialI18nStore = {}
  req.i18n.languages.forEach((l) => {
    initialI18nStore[l] = {}
    namespaces.forEach((ns) => {
      initialI18nStore[l][ns] = req.i18n.services.resourceStore.data[l][ns] || {}
    })
  })

  return {
    i18n: req.i18n, // use the instance on req - fixed language on request (avoid issues in race conditions with lngs of different users)
    initialI18nStore,
    initialLanguage: req.i18n.language
  }
}

module.exports = i18n