i18n.js

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

const options = {
    fallbackLng: 'en',
    load: 'languageOnly', // we only provide en, de -> no region specific locals like en-US, de-DE

    // have a common namespace used around the full app
    ns: ['common'],
    defaultNS: 'common',

    debug: false, //process.env.NODE_ENV !== 'production',
    saveMissing: true,

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

const i18nInstance = i18next;


// for browser use xhr backend to load translations and browser lng detector
if (process.browser) {
    i18nInstance
        .use(XHR)
        // .use(Cache)
        .use(LanguageDetector)
}

// initialize if not already initialized
if (!i18nInstance.isInitialized) {
    console.log('initializing i18next');
    i18nInstance.init(options)
}

// a simple helper to getInitialProps passed on loaded i18next data
const getInitialProps = (req, namespaces) => {
    if (!namespaces) namespaces = i18nInstance.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 = {
    getInitialProps,
    i18nInstance,
    I18n: i18next.default
}