languageDetector.js

import { normalizeLanguage } from './containers/shared/utils'

const queryStringKey = 'lng'
const localStorageKey = 'i18nextLng'
let hasLocalStorageSupport

try {
  hasLocalStorageSupport =
    window !== 'undefined' && window.localStorage !== null
  const testKey = 'i18next.translate.boo'
  window.localStorage.setItem(testKey, 'foo')
  window.localStorage.getItem(testKey)
  window.localStorage.removeItem(testKey)
} catch (e) {
  hasLocalStorageSupport = false
}

const getFromQS = () => {
  if (typeof window !== 'undefined') {
    const query = window.location.search.substring(1)
    const params = query.split('&')
    for (let i = 0; i < params.length; i += 1) {
      const parts = params[i].split('=')
      if (parts[0] === queryStringKey && parts[1]) {
        return normalizeLanguage(parts[1])
      }
    }
  }

  return undefined
}

const getFromLocalStorage = () =>
  hasLocalStorageSupport
    ? normalizeLanguage(window.localStorage.getItem(localStorageKey))
    : undefined

const getFromNavigator = () => {
  const found = []
  let normalized

  if (typeof navigator !== 'undefined') {
    if (navigator.userLanguage) {
      found.push(navigator.userLanguage)
    }
    if (navigator.language) {
      found.push(navigator.language)
    }
    if (navigator.languages) {
      for (let i = 0; i < navigator.languages.length; i += 1) {
        found.push(navigator.languages[i])
      }
    }
  }

  found.every((lang) => {
    normalized = normalizeLanguage(lang)
    return !normalized
  })

  return normalized
}

const languageDetector = {
  init: Function.prototype,
  type: 'languageDetector',
  detect: () =>
    getFromQS() || getFromLocalStorage() || getFromNavigator() || 'en-US',
  cacheUserLanguage: (lng) => {
    window.localStorage.setItem(localStorageKey, lng)
  },
}

export default languageDetector