Coupon Management System API

Objective

This project is a RESTful API designed to manage and apply various types of discount coupons for an e-commerce platform. It provides a robust and extensible system for creating, validating, and applying coupons to a shopping cart, with a focus on clean code, automated testing, and enterprise-ready practices.

Features

CRUD Operations: Full Create, Read, Update, and Delete functionality for coupons.
Multiple Coupon Types: Built-in support for:
- cart-wise: Discounts on the entire cart total.
- product-wise: Discounts on specific products.
- BxGy (Buy X, Get Y): "Buy X items, Get Y items free" promotions.
Time-Based Validity: Coupons can have start and end dates, automatically controlling their active period.
Extensible Logic: A Strategy design pattern allows for the easy addition of new coupon types without modifying existing service logic.
Coupon Applicability: An endpoint to fetch all valid coupons that can be applied to a given cart.
Coupon Application: An endpoint to apply a specific coupon and see the final discounted price.
Robust Validation: Inbound request validation to ensure data integrity.
Centralized Error Handling: Consistent and predictable error responses.
Automated Testing Suite: Unit and integration tests using Jest to ensure reliability.

Technology Stack

Backend: Node.js, Express.js
Database: MongoDB with Mongoose ODM
Logging: Winston
HTTP Logging: Morgan
Validation: Joi
Environment Variables: Dotenv
Testing: Jest, Supertest, MongoDB Memory Server

Project Structure

The project follows a feature-driven, layered architecture to promote separation of concerns and maintainability.

src/
├── config/         # Environment variables, logger, etc.
├── controllers/    # Handles HTTP requests and responses.
├── services/       # Contains the core business logic.
├── routes/         # Defines API endpoints.
├── middleware/     # Custom middleware for validation and error handling.
├── models/         # Mongoose database schemas.
├── utils/          # Shared utility functions (e.g., AppError).
├── strategies/     # Logic for different coupon types.
├── validations/    # Joi schemas for request validation.
├── App.js          # The main Express application setup.
└── index.js        # The application entry point.
tests/
├── integration/    # Integration tests for API routes.
├── unit/           # Unit tests for services, strategies, etc.
└── setup.js        # Test environment setup (in-memory DB).

Setup and Installation

Clone the repository:

git clone https://github.com/fadehack/coupon-management-api
cd coupon-management-api

Install dependencies:
```
npm install
```

Set up environment variables: Create a .env file by copying the example file provided:

cp .env.example .env

Then, update the .env file with your configuration, such as your MongoDB Atlas connection string.

# Server port
PORT=3000

# MongoDB Atlas Connection URI
MONGODB_URI=mongodb+srv://<user>:<password>@cluster.mongodb.net/yourDbName

# Node Environment
NODE_ENV=development

Running the Application & Tests

Run the development server:
```
npm run dev
```
The server will start on the port specified in your .env file (e.g., http://localhost:3000).
Run the automated tests:
```
npm test
```
This will execute all unit and integration tests using Jest and an in-memory MongoDB server.

API Endpoints

All endpoints are prefixed with /v1.