Offline Credit Card Validation Script

credit_card_validator.rb

# Ruby Version: ruby-1.9.2-p290
# Author: Rahul Trikha
# Email: rahul.trikha@gmail.com
# Run: ruby credit_card_validator.rb

class CreditCardValidator
  attr_accessor :card

  def initialize(card=nil)
    sanitize(card)
  end

  def sanitize(card)
    self.card = card.gsub(/\s/,'') unless card.nil?
  end

  def type
    case sanitize(card)
      when /^(34|37)\d{13}$/
        'AMEX'
      when /^6011\d{12}$/
        'Discover'
      when /^5[1-5]\d{14}$/
        'MasterCard'
      when /^4(\d{12}|\d{15})$/
        'VISA'
      else 'Unknown'
    end
  end

  def meet_luhn_verification?
    total = sanitize(card).reverse.split(//).inject([0,0]) do |accum,number|
      number = number.to_i
      accum[0] += (accum[1] % 2 == 0 ? number : rotate(number * 2))
      accum[1] += 1
      accum
    end

    total[0] % 10 == 0
  end

  def rotate(number)
    if number > 9
      number = number % 10 + 1
    end
    number
  end

  def valid?
    (type != "Unkown") && meet_luhn_verification?
  end

  def validity
    valid? ? "valid" : "invalid"
  end

  def to_s
    "#{type}: #{card}".ljust(28) + " (#{validity})"
  end
end

if __FILE__ == $0
  cards = "4111111111111111
           4111111111111
           4012888888881881
           378282246310005
           6011111111111117
           5105105105105100
           5105 1051 0510 5106
           9111111111111111"

  validator = CreditCardValidator.new

  cards.lines.each do |line|
    validator.card = line.chomp.strip
    validator.valid?
    puts validator
  end
end