Account API

How to use it

Tested using Python 3.10.14

pip install -r requirements.txt
fastapi run src/main.py

Routes breakdown

You can run all routes in sequence through postman run collection feature. The postman file is in the project root.

POST: /reset, resets the application state.

GET: /balance?account_id=, returns the current balance of account if present.

POST: /event, which have 3 types:

• deposit: deposits amount to account if account does not exists, otherwise increments the current balance.
• withdraw: withdraws amount from account if account exists and amount is less than or equal than current balance.
• transfer: transfer amount from origin to destination. If origin does not exists or origin balance is less than amount, returns error. If destination does not exists, creates the destination account, deposits amount to destination and withdraws from origin.

Patterns applied

• Repository pattern (AccountRepository): The Facade Pattern provides a simplified interface to a set of subsystems.
• Service pattern (EventService): Encapsulates business logic into service classes to keep your endpoints simple and reusable.
• Singleton Pattern (Database): The pattern ensures that only one instance of the class is created. If an instance already exists, the pattern provides access to that same instance.
• Validation Pattern (AccountRepository, field_validator): FastAPI provides built-in validation using Pydantic models. To test this, try making a deposit where the destination is an integer instead of a string or amount is less than or equal zero.
• Error handling pattern (search for raise): Good error handling ensures robust APIs.
• Observer pattern (consume_messages.py): Allows components to subscribe to events and get notified when something changes. Everytime an account receives a deposit or transfer, the account's owner is notified.

Test it

Run the tests using python3 -m unittest tests/test_db_wrapper.py