The initial code is located in the initial-code branch and is a simple implementation of the API for a hotel reservation system using Axum server.
Using the API, it is possible to:
- get all reservations;
- create a new reservation for new and existing customers;
- cancel a reservation by deleting it.
After the creating or cancelling a reservation, the server sends a confirmation email to the client.
All messages sent by the server are logged in the data storage outbox.
The API is tightle coupled with the implementation of the in-memory database (HashMap) and with the implementation of the mailer service. The server can send emails only.
The goal of the challenge is to refactor the code to make it more modular, testable, and maintainable. The code should be refactored to use the repository pattern to abstract the data storage, and the mailer service should be abstracted to allow for different implementations. The latter be able to send not only emails but also other types of messages.
Each API endpoint handler has a corresponding test and the tests should still pass after the refactoring.