Author: Alan Dinneen
Date: 12/6/15
Name: CCProcessing

########## DEPENDANCES ##########
Python 2.7 Installed
Non-original libraries used are all core Python libraries. They are as follows:
    1) unittest
    2) fileinput
    3) re


########## RUN INSTRUCTIONS ##########
To run the core application from command line:
    1) cd credit_card_processing
    2) python2.7 runapp.py < input.txt

To run all of the unit tests from command line:
    1) cd credit_card_processing
    2) python2.7 -m unittest discover


########## OVERVIEW ##########
Python was picked as the language for this application because it is my most
frequently used language and the one I am most comfortable in. 
Python 2.7 was picked as it is installed by default on a lot of modern systems.
All libraries used or built where picked for the application's ease of use.
Using core Python libraries or custom packages makes it so that a virtual environment
and other requirements are not necessary.This makes the script very easy to run 
out of the box.  

When designing the ccacc package, more specifically the account module, I made a
few key decisions. First I made the initialization parameters non optional. I did 
this because I do not see that there should ever be an account without a name,
credit card number, or credit limit. Credit card numbers are validated at initialization
to avoid having to process the card number every time a transaction occurs. Any account
with an invalid credit card number can not successfully complete any transaction methods.
Since this credit card validation is a core design principle and Python doesn't have private variables,
a property decorator was added to the credit card number variable in the Account class. This was done so that 
if the credit card number needs to be updated, it will still go through the validation method even after the account object
has been created. The credit limit variable inside the Account class exposes the same functionality as the credit
card number described above.

Seperating the Account module into its own package was done in order to help with future development.
Since the application is seperated out into distinct packages, it is easy to add any new modules to the
ccacc package or entire new pacakges to the application. 

I've included two unit tests. test_runapp tests all the methods in the main application. 
test_ccacc tests all the Account class methods and thier possible outcomes.