GSoC Project on Credits Management

I’m Udith Gunaratna, a Computer Science & Engineering undergraduate of University of Moratuwa, Sri Lanka. I’m looking forward to participate in this year’s GSoC for the first time. I’m particularly interested in the idea on designing an API to manage credits. Can someone recommend some resources for me to refer in order to get a good understanding of the overall code as well as the parts relevant for the above mentioned project.

Thank you in advance!