module Iz
  class CreditCard
    REGEX = /^(?:(4[0-9]{12}(?:[0-9]{3})?)|(5[1-5][0-9]{14})|(6(?:011|5[0-9]{2})[0-9]{12})|(3[47][0-9]{13})|(3(?:0[0-5]|[68][0-9])[0-9]{11})|((?:2131|1800|35[0-9]{3})[0-9]{11}))$/

    attr_accessor :number

    def initialize(credit_card_number)
      self.number = credit_card_number
    end

    def valid?
      Iz::CreditCard.is_credit_card?(number)
    end

    def self.is_credit_card?(number)
      number.to_s =~ REGEX
    end
  end
end