Simple Money Transfer Example Using Kotlin

Frameworks Used

• Kotlin
• Ktor (Framework for building asynchronous servers and clients in connected systems using kotlin)
• Koin (Dependency Injection)
• jetbrains exposed
• H2 db as inmemory data storage
• uchuhimo (for Config)
• Flyway (For database migration)

Data Model Concept

The implementation show only the transfer part out of the huge process , ignoring any other before and after processing

Portfolio is the wallet that is owned by user/s(can be shared between multiple users, but has only one registered owner) and it's related to the customer by a contract(business partner) portfolio can have one or many positions (1->m relationship)

Entities represented in the sample:

Position:
It represents the assets information including asset type , portfolio , account type(ex: money account) current balance ...etc Ideally , position/asset type should have it's own entities, but for simplicity and this point is out of the task scope i decided to implement them as enums

Transfer:
The transfer in our case is being implemented in direct way , in real world , it should be stored and triggered (cron job for example) in certain time frame , or waiting response from other service and then update the balances

How to start?

• Please Generate self contained Jar (gradle clean build is good option :D )

• Start the server by java -jar build/libs/Revolute.jar

• Use Curl or Insomnia (it's cool) to trigger your calls

• Code is covered by Tests (Please approach me for clarifications)-(hit ./gradlew test will not bite :D)

• Hint , Use the following Endpoints to navigate (Don't worry you are almost covered)

  GET   "/api/positions/{id}"        -> Get position by id
  GET   "/api/positions"             -> Get All positions/you can decided if u want blocked/locked positions too
  POST  "/api/positions"             -> Create new Position
  PATCH "/api/positions/block/{id}"  -> block Position
  PATCH "/api/positions/unblock/{id}"-> unblock Position
  POST  "/api/transfer"              -> Make transfer
  GET   "/api/transfer/{id}"         -> Get transfer
  

For Concurrency :

 https://blog.mindorks.com/mastering-kotlin-coroutines-in-android-step-by-step-guide 
           (It's very cool illustration of concurrency in kotlin coroutines)