luhnacy

= luhnacy

A tiny (hopefully) gem that will automate some of the painful tasks of generating / validating strings of numbers based on the Luhn algorithm (e.g. credit card numbers, ID numbers).

== Usage

To require:

require 'luhnacy'

=== Generic Validation\Generation

To validate:

Luhnacy.valid?('49927398716')

To generate a string of 10 digits that satisfies the Luhn algorithm:

valid_string = Luhnacy.generate(10)

To generate a string of 10 digits that does not satisfy Luhn algorithm:

invalid_string = Luhnacy.generate(10, :invalid => true)

To generate a string of 10 digits that satisfies Luhn and starts with predefined characters:

Luhnacy.generate(10, :prefix => '12345') #=> "1234597480"

=== Named Generators/Validators

There are named validators and generators for Visa, Mastercard and American Express credit cards. Note: Visa validation/generation only works for 16-digit credit card numbers.

Also, there is also a named generator for the National Provider Identifier (thanks to Taylor Yelverton) used in the US to identify health care providers - see example usage section.

Example usage (mastercard)

To validate a mastercard:

Luhnacy.mastercard?("5176290135048779")

To generate a mastercard number that satisfies Luhn:

Luhnacy.mastercard #=> "5151199732615386"

To generate a master card number that does not satisfy Luhn:

Luhnacy.mastercard(:invalid => true)

Similar usage exists for Visa, American Express and NPI:

Luhnacy.visa Luhnacy.visa?

Luhnacy.amex Luhnacy.amex?

Luhnacy.doctor_npi Luhnacy.doctor_npi?

== Planned changes

At some point it may make sense to store the patterns for the named generator in a seperate class/module or even in a YAML file. This will be driven by the need for additional named generators. If a YAML file is used, then the very next release may also include the ability to pass Luhnacy a custom YAML file for generating/validating strings.

== Note on Patches/Pull Requests

• Fork the project.
• Make your feature addition or bug fix.
• Add tests for it. This is important so I don't break it in a future version unintentionally.
• Commit, do not mess with rakefile, version, or history. (if you want to have your own version, that is fine but bump version in a commit by itself I can ignore when I pull)
• Send me a pull request. Bonus points for topic branches.

== Sources

• http://blog.flame.org/2008/3/24/checking-credit-card-numbers-in-ruby
• http://www.missiondata.com/blog/web-development/25/credit-card-type-and-luhn-check-in-ruby/
• http://en.wikipedia.org/wiki/Luhn
• http://www.darkcoding.net/credit-card-numbers/
• http://en.wikipedia.org/wiki/Credit_card_number

== Copyright

Copyright (c) 2010 Rory McKinley. See LICENSE for details.