src › common › i18n › index.js

export const defaultLang = "en";

export const supportedLangs = {
  en: "English",
  ar: "Arabic (عربي)",
};

export function determineUserLang(acceptedLangs, path = null) {
  // check url for /en/foo where en is a supported language code
  if (path !== null) {
    const urlLang = path.trim().split("/")[1];

    const matchingUrlLang = findFirstSupported([stripCountry(urlLang)]);

    if (matchingUrlLang) {
      return matchingUrlLang;
    }
  }

  // check browser-set accepted langs
  const matchingAcceptedLang = findFirstSupported(
    acceptedLangs.map(stripCountry),
  );

  return matchingAcceptedLang || defaultLang;
}

function findFirstSupported(langs) {
  const supported = Object.keys(supportedLangs);

  return langs.find(code => supported.includes(code));
}

function stripCountry(lang) {
  return lang
    .trim()
    .replace("_", "-")
    .split("-")[0];
}