module Money::Helpers

def value_to_currency(currency)
  case currency
  when Money::Currency, Money::NullCurrency
    currency
  when nil, ''
    default = Money::Config.current.currency
    raise(Money::Currency::UnknownCurrency, 'missing currency') if default.nil? || default == ''
    value_to_currency(default)
  when 'xxx', 'XXX'
    Money::NULL_CURRENCY
  when String
    begin
      Currency.find!(currency)
    rescue Money::Currency::UnknownCurrency => error
      if Money::Config.current.legacy_deprecations
        Money.deprecate(error.message)
        Money::NULL_CURRENCY
      else
        raise error
      end
    end
  else
    raise ArgumentError, "could not parse as currency #{currency.inspect}"
  end
end