Classe pra validar número do CNS / Cartão Nacional de Saúde / Cartão SUS

c_n_s.rb

# frozen_string_literal: true

##
# Inspired by http://www.yanaga.com.br/2012/06/validacao-do-cns-cartao-nacional-de.html and https://github.com/fnando/cpf_cnpj
#
# @example Basic usage
#
#     CNS.new("187507943600018").valid? # true
#     CNS.new("187 5079 4360 0018").valid? # false
#     CNS.new("187507943600010").valid? # false
#     CNS.new("187507943600010").formatted # 187507943600010
#     CNS.new("187507943600018").formatted # 187 5079 4360 0018
#
# @todo add option to validation to be strict or not
class CNS
  def initialize(number)
    @number = number
  end

  def formatted
    return @number.insert(11, ' ').insert(7, ' ').insert(3, ' ') if valid?
    @number
  end

  def valid?
    if @number =~ /\A[1-2]\d{10}00[0-1]\d\z/ || @number =~ /\A[7-9]\d{14}\z/
      return CNS.weighted_sum(@number) % 11 == 0
    end
    false
  end
  
  def self.weighted_sum(s)
    soma = 0
    s.each_char.with_index do |c, i|
      soma += c.to_i * (15 - i)
    end
    soma
  end
end