Active Merchant is a simple payment abstraction library extracted from Shopify.

Active Merchant is an extraction from the ecommerce system Shopify. Shopify's requirements for a simple and unified API to access dozens of different payment gateways with very different internal APIs was the chief principle in designing the library.It was developed for usage in Ruby on Rails web applications and integrates seamlessly as a Rails plugin, but it also works excellently as a stand alone Ruby library.