Credit Card Processing (BT Code Challenge)

Overview of design decisions

The program's executable is housed at bin/credit_card_processing, as this is a standard pattern for Ruby libraries (putting the executable in the library's bin/ or exe/ directory).

The program logic lives within lib/credit_card_processing. I created 3 primary classes: CreditCard and Activity.

CreditCard has instance methods #charge and #credit, which are also accessible via CreditCard::Charge and CreditCard::Credit respectively. (These 2 classes are kind of like wrappers and aren't necessary strictly speaking, but I like the idea of "initializing a charge or credit object" where the card being charged or credited is provided as an argument to CreditCard::Charge.new(the_credit_card_to_charge) as I think it is more legible this way.)

The Activity class is responsible for taking an activiy string, e.g. "Add Tom 000000 $1000", and attempting to convert that activity into the appropriate domain objects.

Invoking Activity#save with an activity string of "Add Tom 000000 $1000" should attempt to store a new credit card with cardholder name of "Tom", and a credit limit of $1000.

Finally, the Runner class manages the state of the import of transaction data from the input file. It is kind of like a bridge between Activity and CreditCard. It keeps track of a little bit of its own state, e.g. the names of the cardholders who have activity in the provided inputs. This is relevant in situations where, e.g. Tom's aforementioned credit card has an invalid number, and so we do not store that card's information, but we need to report something like Tom: error in the output when running our program.

Why I chose Ruby

I am most familiar with Ruby and feel very comfortable writing "proper", test-driven, object-oriented code that is highly legible and easy to read.

How to run the code and tests

From archive file

1. Locate the archive file cc_processing.zip (sent as email attachment to Braintree).
2. Unarchive the source code: unzip cc_processing.zip
3. Move into the library directory: cd cc_processing
4. bundle install to setup dependencies
5. To run the program: bin/credit_card_processing spec/fixtures/input.txt, or bin/credit_card_processing < spec/fixtures/input.txt.
6. To run the tests: bin/rspec or bundle exec rspec

From source

1. Clone this repo: git clone git@github.com:mecampbellsoup/cc_processing.git
2. Move into the library directory: cd cc_processing
3. bundle install to setup dependencies
4. To run the program: bin/credit_card_processing spec/fixtures/input.txt, or bin/credit_card_processing < spec/fixtures/input.txt.
5. To run the tests: bin/rspec or bundle exec rspec