index.ts

import i18next, { LanguageDetectorModule } from 'i18next'
import { initReactI18next } from 'react-i18next'
import { NativeModules, Platform } from 'react-native'

import { languages } from './locale/languages'

declare module 'react-i18next' {
	interface CustomTypeOptions {
		resources: typeof languages['en-US']
	}
}

const fallbackLang = 'en-US'

const detectOSLanguage = () => {
	const locale: string | undefined =
		Platform.OS === 'ios'
			? NativeModules?.SettingsManager?.settings?.AppleLanguages[0] // iOS 13
			: NativeModules?.I18nManager?.localeIdentifier
	let lang = locale?.replace('_', '-')
	// the "en-" check is for weird locales like en-FR
	if (lang?.startsWith('en-') && !languages.hasOwnProperty(lang)) {
		lang = 'en-US'
	}
	if (!lang || !languages.hasOwnProperty(lang)) {
		lang = fallbackLang
	}
	return lang
}

const RNLanguageDetector: LanguageDetectorModule = {
	type: 'languageDetector',
	init: () => {},
	detect: detectOSLanguage,
	cacheUserLanguage: () => {},
}

export const initI18N = () =>
	i18next
		.use(RNLanguageDetector)
		.use(initReactI18next)
		.init({
			fallbackLng: fallbackLang,
			resources: languages,
			returnEmptyString: false,
		})
		.then()
		.catch(e => {
			console.log('failed to init i18n:', e)
		})