Ruby On Rails Validator CNPJ

CNPJ Validator Rails

class CnpjValidator < ActiveModel::EachValidator
  class InvalidCNPJ < StandardError; end

  EXPECTED_FORMAT = /^\d{2}\.\d{3}\.\d{3}\/\d{4}\-\d{2}$/

  FIRST_CHECKER_DIGITS_MULTIPLIERS = [5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2]
  SECOND_CHECKER_DIGITS_MULTIPLIERS = [6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2]

  def validate_each(record, attribute, value)
    return unless value.present?
    @record, @attribute, @value = [record, attribute, value]
    validates_data
  rescue InvalidCNPJ => e
    @record.errors[@attribute] << e.message
  end

  private

  def validates_data
    unless @value.match?(EXPECTED_FORMAT) && valid_digits?
      raise InvalidCNPJ.new(options[:message] || "is not a valid CNPJ")
    end
  end

  def valid_digits?
    number, check = @value.gsub(/\.|\//, '').split('-')
    first_checker_digit = discover_checker_digit(number, FIRST_CHECKER_DIGITS_MULTIPLIERS)
    number += first_checker_digit.to_s
    second_checker_digit = discover_checker_digit(number, SECOND_CHECKER_DIGITS_MULTIPLIERS)
    check == "#{first_checker_digit}#{second_checker_digit}"
  end

  def discover_checker_digit(number, digits_multipliers)
    multiplied_values = number.split('').map.with_index do |num, index|
      num.to_i * digits_multipliers[index]
    end
    division = multiplied_values.sum % 11
    division < 2 ? 0 : (11 - division)
  end
end