Technical Documentation: Wallet System

Introduction

This documentation outlines the design and implementation of a simple wallet system. The wallet system allows users to perform Account crediting, Account Debit and make Transfer

Technologies Used

• Node.js - es6+
• ExpressJs
• TypeScript
• Mongoose (ODM for MongoDB) - explicit schema definitions.
• Jest
• pino

Decision

• Created two models: users and accounts.
  • Users model store users information (name, email and _id)
  • Account model store wallet data (accountId, active, balance)
  • accountId points to user(_id - ObjectId)

Installation and Setup

1. Clone the Repository:

• git clone https://github.com/mbanda1/my-wallet.git
• cd my-wallet
• npm install

2. Environment Variables:

I hardcoded .env, you may change configuration details.

PORT=3000
MONGO_URI=mongodb://localhost:27017/wallet_db

1. Start

   • npm run dev - this will also seeds initial users (we ned userId to serve as account numbers)

2. Build

   • npm run build

API Endpoints

The wallet system exposes the following API endpoints for wallet operations:

1. Credit Wallet Account

URL: /api/wallet/credit Method: POST Request Body:

Request

{
    "accountId": "65fd89474821cebc7d79a683",
    "amount": 2000
}

Response

{
    "_id": "65fdb885700e471e27588e62",
    "accountId": "65fdaaefa39c90915498209d",
    "__v": 0,
    "active": true,
    "balance": 3,
    "updatedAt": "2024-03-22T16:57:41.855Z"
}

2. Debit Wallet Account URL: /api/wallet/debit Method: POST Request Body:

Request

{
    "accountId": "65fd89474821cebc7d79a683",
    "amount": 2
}

Response

{
    "_id": "65fdb885700e471e27588e62",
    "accountId": "65fdaaefa39c90915498209d",
    "__v": 0,
    "active": true,
    "balance": 1,
    "updatedAt": "2024-03-22T16:57:41.855Z"
}

1. Make transaction - account transfer URL: /api/transaction/send Method: POST Request Body:

Request

{
    "creditAccountId": "65fdaaefa39c90915498209e",
    "debitAccountId": "65fdaaefa39c90915498209d",
    "amount": 1
}

Response

{
    "debitAccount": {
        "_id": "65fdb885700e471e27588e62",
        "accountId": "65fdaaefa39c90915498209d",
        "__v": 0,
        "active": true,
        "balance": 0,
        "updatedAt": "2024-03-22T16:57:41.855Z"
    },
    "creditAccount": {
        "_id": "65fdbf0b700e471e275892e5",
        "accountId": "65fdaaefa39c90915498209e",
        "__v": 0,
        "active": true,
        "balance": 1,
        "updatedAt": "2024-03-22T17:25:31.143Z"
    }
}

Error Handling

The wallet system implements proper error handling by providing meaningful error messages in the response body along with appropriate HTTP status codes for different error scenarios.

Tests

• run npm run test

Implemented unit test for all services with jest.

Logging

Used different log levels (e.g., INFO, WARN, ERROR) to categorize log messages based on their importance. Utilized Pino a fast and low overhead Node.js logger.