class CvrValidator

# File lib/cvr_validator.rb, line 4
def validate_each(record, attribute, value)
  return record.errors.add(attribute, :blank) if value.blank?

  digits = convert_to_digits(value)

  record.errors.add(attribute, :too_short) if digits.length < 8
  record.errors.add(attribute, :too_long) if digits.length > 8
  record.errors.add(attribute, :bad_format) unless value.match?(/\A[\s\d-]+\z/)
  record.errors.add(attribute, :invalid_cvr_number) unless valid_check_digit?(digits)
end

# File lib/cvr_validator.rb, line 28
def convert_to_digits(value)
  value.to_s.gsub(/\D/, "").chars.map(&:to_i)
end

# File lib/cvr_validator.rb, line 17
def valid_check_digit?(digits)
  serial = digits[0, 7]
  expected_check_digit = digits[-1]

  weighted_serials = serial.zip(MOD_11_WEIGHTS).map { |digit, weight| digit * weight }
  mod = weighted_serials.sum % 11
  actual_check_digit = mod.zero? ? 0 : 11 - mod

  actual_check_digit == expected_check_digit
end