Antaeus

Antaeus (/ænˈtiːəs/), in Greek mythology, a giant of Libya, the son of the sea god Poseidon and the Earth goddess Gaia. He compelled all strangers who were passing through the country to wrestle with him. Whenever Antaeus touched the Earth (his mother), his strength was renewed, so that even if thrown to the ground, he was invincible. Heracles, in combat with him, discovered the source of his strength and, lifting him up from Earth, crushed him to death.

Welcome to our challenge.

The challenge

As most "Software as a Service" (SaaS) companies, Pleo needs to charge a subscription fee every month. Our database contains a few invoices for the different markets in which we operate. Your task is to build the logic that will schedule payment of those invoices on the first of the month. While this may seem simple, there is space for some decisions to be taken and you will be expected to justify them.

Instructions

Fork this repo with your solution. Ideally, we'd like to see your progression through commits, and don't forget to update the README.md to explain your thought process.

Please let us know how long the challenge takes you. We're not looking for how speedy or lengthy you are. It's just really to give us a clearer idea of what you've produced in the time you decided to take. Feel free to go as big or as small as you want.

Developing

Requirements:

• >= Java 11 environment

Building

./gradlew build

Running

There are 2 options for running Anteus. You either need libsqlite3 or docker. Docker is easier but requires some docker knowledge. We do recommend docker though.

Running through docker

Install docker for your platform

make docker-run

Running Natively

Native java with sqlite (requires libsqlite3):

If you use homebrew on MacOS brew install sqlite.

./gradlew run

App Structure

The code given is structured as follows. Feel free however to modify the structure to fit your needs.

├── pleo-antaeus-app
|       main() & initialization
|
├── pleo-antaeus-core
|       This is probably where you will introduce most of your new code.
|       Pay attention to the PaymentProvider and BillingService class.
|
├── pleo-antaeus-data
|       Module interfacing with the database. Contains the database models, mappings and access layer.
|
├── pleo-antaeus-models
|       Definition of the "rest api" models used throughout the application.
|
├── pleo-antaeus-rest
|        Entry point for REST API. This is where the routes are defined.
└──

Main Libraries and dependencies

• Exposed - DSL for type-safe SQL
• Javalin - Simple web framework (for REST)
• kotlin-logging - Simple logging framework for Kotlin
• JUnit 5 - Testing framework
• Mockk - Mocking library
• Sqlite3 - Database storage engine

Happy hacking 😁!

Key design decisions with reasons:

Scheduler

Scheduler is started in the app from the startScheduler() method It sets a timer for the 1st of next month. On the first of each month, a startBilling() is triggered

startBilling() iterates through all the pending invoices and attempts to charge them. At the end it again calls startScheduler() to set the next months timer

doBilling

In case of a successful transaction, the status of the invoice is changed to PAID In case of an exception or error, the status is changed to FAILED. (these invoices should be checked again later for issues)

• Adding an invoice status FAILED also helps keep a track of "actually" PENDING invoices

If an invoice is being attempted to be paid, its status is changed to INPROGRESS This is done, taking the assumption that in a production scenario, there will be several stateless servers attempting to pay the invoice at the same time