language.ts

export function matchLanguages(
  languages: string[],
  acceptLanguages: readonly string[],
): string | null {
  {
    // const lang = acceptLanguages.map(userLang => languages.find(lang => lang.startsWith(userLang))).filter(v => !!v)[0]
    // TODO: Support es-419, remove this code if we include spanish country variants
    const lang = acceptLanguages
      .map(userLang =>
        languages.find(currentLang => {
          if (currentLang === userLang) return currentLang

          // Edge browser: case for ca-valencia
          if (currentLang === 'ca-valencia' && userLang === 'ca-Es-VALENCIA') return currentLang

          if (userLang.startsWith('es-') && userLang !== 'es-ES' && currentLang === 'es-419')
            return currentLang

          return currentLang.startsWith(userLang) ? currentLang : undefined
        }),
      )
      .find(v => !!v)
    if (lang) return lang
  }

  const lang = acceptLanguages
    .map(userLang => {
      userLang = userLang.split('-')[0]!
      return languages.find(lang => lang.startsWith(userLang))
    })
    .find(v => !!v)
  if (lang) return lang

  return null
}