module FFaker::Bank

def check_country_existence(country_code)
  unless COUNTRIES.keys.include?(country_code.upcase)
    raise ArgumentError, "Unexpected country code: '#{country_code}'"
  end
end

def formatify_iban(code)
  FFaker.bothify(code).upcase
end

def iban(country_code: nil)
  return formatify_iban(fetch_sample(COUNTRIES.values)) unless country_code
  check_country_existence(country_code)
  formatify_iban(COUNTRIES[country_code.upcase])
end