From: Mike Moore <blowmage@...>
Date: 2007-05-01T01:38:59+09:00
Subject: [SOLUTION] [QUIZ] Checking Credit Cards (#122)

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This is my first submission to Ruby Quiz.

I have all the credit card rules in an external YAML file.  I also think
that my luhn() and type() implementations could be cleaner, but it is what
it is.  :)

----------------------------------------

# ccard.yaml

Visa:             { starts: [ '4' ],
                    sizes: [ 16, 13 ] }
MasterCard:       { starts: [ '51', '52', '52', '54', '55' ],
                    sizes: [ 16 ] }
Discover:         { starts: [ '6011' ],
                    sizes: [ 16 ] }
American Express: { starts: [ '34', '37' ],
                    sizes: [ 15 ] }

----------------------------------------

# ccard.rb

# Credit Card Validation
# Ruby Quiz #122 - http://www.rubyquiz.com/quiz122.html
# By Mike Moore - http://blowmage.com/

require 'yaml'

class CreditCard
  def CreditCard.luhn(cc)
    multi = 1
    nums = cc.gsub(/\D/, '').reverse.split('').collect do |num|
      num = num.to_i * (multi = (multi == 1) ? 2 : 1)
    end
    total = 0
    nums.join.split('').each do |num|
      total += num.to_i
    end
    total
  end

  def CreditCard.valid?(cc)
    (CreditCard.luhn(cc) % 10) == 0
  end

  def CreditCard.type(cc)
    cc.gsub!(/\D/, '')
    YAML::load(open('ccard.yaml')).each do |card, rule|
      rule['starts'].each do |start|
        if (cc.index(start.to_s) == 0)
          return card if rule['sizes'].index(cc.size)
        end
      end
    end
    'Unknown'
  end

  def initialize(cc)
    @number = cc.gsub(/\D/, '')
  end

  def number
    @number
  end

  def number=(cc)
    @number = cc.gsub(/\D/, '')
  end

  def valid?
    CreditCard.valid? @number
  end

  def type
    CreditCard.type @number
  end
end

if __FILE__ == $0
  cc = CreditCard.new ARGV.join
  puts "You entered the following credit card number: #{cc.number}"
  puts "The number is for a #{cc.type} credit card"
  puts "The number is #{cc.valid? ? 'Valid' : 'Not Valid'}"
end

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