lanrey/fincra-backend-api

Backend api for fincra test

Node.js RESTful API with TypeScript and MongoDB

This project is a simple RESTful API built with Node.js and TypeScript, using MongoDB as the database. It provides endpoints to create and manage products in a store.

Table of Contents

• Features
• Prerequisites
• Installation
• Usage
• Endpoints
• Contributing
• License

Features

• Credit a user wallet.
• Debit a user wallet.
• Check user balance.
• MongoDB for efficient data storage.

Prerequisites

Before you begin, ensure you have met the following requirements:

• Node.js and npm installed.
• MongoDB server running locally or provide a connection URI.

Installation

1. Clone the repository:

   git clone https://github.com/Lanrey/fincra-backend-api

2. Install dependencies:

    npm install

3. Create a .env file in the root directory and add the following environment variables:

PORT=3000

MONGO_URI=mongodb://localhost:27017/fincra_backend_test

Usage

1. Start the server:

   npm start

2. Navigate to http://localhost:3000/ to access the API.

Endpoints

Method	Endpoint	Description	Authentication
POST	/api/wallet/credit	Credit a user wallet	No
POST	/api/wallet/debit	Debit a user wallet	No
GET	api/wallet/balance	Get wallet balance of user	No

Postman Documentation link Live API

Environment

Create a .env file in the root directory and add the following environment variables:

NODE_ENV=DEV
MONGO_URI_DEV=<A hosted mongodb database>
JWT_SECRET=<secret>

## Technical Documentation for Wallet System

### Overview

The wallet system is a RESTful API developed using Node.js and TypeScript. It provides endpoints to credit, debit, and retrieve the balance from a user-specific digital wallet. The system uses MongoDB for data persistence, ensuring robust and scalable storage of wallet balances.

### System Architecture

#### Technologies Used

- **Node.js**: Chosen for its non-blocking I/O model which is ideal for data-intensive real-time applications that run across distributed devices.
- **TypeScript**: Provides static typing to ensure reliability and predictability of the code, which is crucial for financial transactions.
- **Express**: A minimal and flexible Node.js web application framework that provides a robust set of features to develop web and mobile applications.
- **MongoDB**: A NoSQL database known for its high performance, high availability, and easy scalability.
- **Mongoose**: An ODM (Object Data Modeling) library for MongoDB and Node.js that provides a straight-forward, schema-based solution to model application data.
- **Express-validator**: Middleware that uses a set of comprehensive validators and sanitizers to validate and sanitize data coming from the client side.

### API Design

The API consists of three main endpoints:

1. **POST /wallet/credit**: Credits an amount to the user’s wallet.
2. **POST /wallet/debit**: Debits an amount from the user’s wallet.
3. **GET /wallet/balance**: Retrieves the current balance of the user’s wallet.

Each endpoint uses validation middleware to ensure the integrity and correctness of the input data before processing.

### Concurrency Handling

To manage concurrency effectively and prevent race conditions during credit and debit operations, we used the `async-mutex` package. This package provides mutual exclusion control (mutex) which ensures that only one operation can manipulate the wallet balance at a time, thus maintaining data consistency.

### Data Validation

Input validation is implemented using `express-validator`. This ensures that all incoming data on critical fields (`userId` and `amount`) adheres to expected formats and meets defined constraints (e.g., `amount` must be a positive number). This validation step prevents common data errors and security issues such as injection attacks.

### Error Handling

Robust error handling is integrated throughout the application. Each endpoint is capable of responding with appropriate HTTP status codes and error messages that describe issues in a clear and actionable manner. This ensures that the client-side can properly handle errors and provide feedback to the user.

### Security Measures

Basic security measures implemented include:
- **Input Validation**: Ensures all incoming data is correct and safe to process.
- **Environment Variables**: Sensitive information such as database credentials are stored in environment variables, not in the codebase.

### Documentation and Testing

- **Inline Comments**: The codebase includes detailed comments explaining the purpose and logic of code blocks, functions, and modules.
- **API Documentation**: Created using Postman, providing a convenient way to interact with the API during development and testing phases.