Validador de CPF

validador_cpf.rb

class ValidadorCPF

  REGEX = /\A(\d{3}\.?){2}\d{3}\-?\d{2}\Z/

  def self.valido?(cpf)
    return false unless REGEX =~ cpf

    arr = cpf.scan(/\d/).take(9)

    arr << calcular_dv(arr)
    arr << calcular_dv(arr)

    cpf.scan(/\d/).join == arr.join
  end

  def self.calcular_dv(arr)
    arr2 = arr.reverse.each_with_index.map { |item, index| (index + 2) * item.to_i }
    val = arr2.reduce(:+)

    mod = val % 11

    if mod < 2
      0
    else
      11 - mod
    end
  end
end