class LanguageContext
  def key
    :lang
  end

  def required?
    false
  end

  def constraints
    Regexp.new(I18n.available_locales.join('|'))
  end

  def default
    I18n.default_locale
  end

  def current
    I18n.locale
  end

  def apply(controller, value)
    I18n.locale = value || controller.params[key].presence || default
  end

  def url_option
    current unless current == default
  end
end