egonsaks / intern-decision-engine-backend

InBank Backend Service

This service provides a REST API for calculating an approved loan amount and period for a customer. The loan amount is calculated based on the customer's credit modifier, which is determined by the last four digits of their ID code.

Technologies Used

• Java 17
• Spring Boot
• estonian-personal-code-validator:1.6

Requirements

• Java 17
• Gradle

Installation

To install and run the service, please follow these steps:

1. Clone the repository.
2. Navigate to the root directory of the project.
3. Run gradle build to build the application.
4. Run java -jar build/libs/inbank-backend-1.0.jar to start the application

The default port is 8080.

Endpoints

The application exposes a single endpoint:

POST /loan/decision

The request body must contain the following fields:

• personalCode: The customer's personal ID code.
• loanAmount: The requested loan amount.
• loanPeriod: The requested loan period.

Request example:

{
"personalCode": "50307172740",
"loanAmount": "5000",
"loanPeriod": "24"
}

The response body contains the following fields:

• loanAmount: The approved loan amount.
• loanPeriod: The approved loan period.
• errorMessage: An error message, if any.

Response example:

{
"loanAmount": 2400,
"loanPeriod": 24,
"errorMessage": null
}

Error Handling

The following error responses can be returned by the service:

• 400 Bad Request - in case of an invalid input
  • Invalid personal ID code! - if the provided personal ID code is invalid
  • Invalid loan amount! - if the requested loan amount is invalid
  • Invalid loan period! - if the requested loan period is invalid
• 404 Not Found - in case no valid loans can be found
  • No valid loan found! - if there is no valid loan found for the given ID code, loan amount, and loan period
• 500 Internal Server Error - in case the server encounters an unexpected error while processing the request
  • An unexpected error occurred - if there is an unexpected error while processing the request

Architecture

The service consists of two main classes:

• DecisionEngine: A service class that provides a method for calculating an approved loan amount and period for a customer.
• DecisionEngineController: A REST endpoint that handles requests for loan decisions.