PaymentAPI build on Flask Framework

PaymentAPI is an API which is built by Flask (Python Web Framework).

Write a Flask Web API with only 1 method called “ProcessPayment” that receives a request like this

• CreditCardNumber (mandatory, string, it should be a valid credit card number)
• CardHolder: (mandatory, string)
• ExpirationDate (mandatory, DateTime, it cannot be in the past)
• SecurityCode (optional, string, 3 digits)
• Amount (mandatoy decimal, positive amount)

The response of this method should be 1 of the followings based on

• Payment is processed: 200 OK
• The request is invalid: 400 bad request
• Any error: 500 internal server error

The payment could be processed using different payment providers (external services) called:

• PremiumPaymentGateway
• ExpensivePaymentGateway
• CheapPaymentGateway.

The payment gateway that should be used to process each payment follows the next set of business rules: a) If the amount to be paid is less than £20, use CheapPaymentGateway. b) If the amount to be paid is £21-500, use ExpensivePaymentGateway if available. Otherwise, retry only once with CheapPaymentGateway. c) If the amount is > £500, try only PremiumPaymentGateway and retry up to 3 times in case payment does not get processed.

Recommendations:

• The classes should be written in such way that they are easy to test.
• Write as many tests as you think is enough to be certain about your solution works - Use SOLID principles.
• Decouple the logic the prediction logic from the API as much as possible

Installation

Creating Virtual Environment

mkdir myproject
cd myproject
python3 -m venv venv

Then installing the Flask library:

pip install Flask

unittest

Just go to test folder to post the JSON data and check the result.

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.