KarimAziev / nestjs-pay-shop

A basic implementation of an online web shop using NestJS

About

This project provides a basic implementation of an online webshop capable of processing orders with multiple payment options, including Stripe, PayPal, and Braintree. The architecture is designed to allow for easy addition or removal of payment providers.

Table of Contents

• About
  • Architecture Overview
  • Implementation Details
  • Running the Project
  • Extending the System

Architecture Overview

The webshop is built using NestJS. The architecture is structured into modules, with adherence to the principles of modularity and single responsibility.

Key Design Decisions

• Strategy Pattern for Payment Processing: This pattern allows for the addition of new payment methods without significantly altering the existing codebase, promoting easy maintenance and scalability.
• Factory Pattern for Strategy Instantiation: A factory is utilized to dynamically create instances of payment strategies based on the customer's choice, further decoupling the system components.
• Module-Based Structure: NestJS modules encapsulate specific functionalities, facilitating better organization and modular growth of the application.

Project Structure

src/
|-- app.module.ts          # Root module, imports other modules
|-- main.ts                # Application bootstrap
|-- orders/                # Orders module, handles order processing
|   |-- interfaces/
|   |-- orders.controller.ts
|   |-- orders.module.ts
|   `-- orders.service.ts  # Hypothetical service for order management
|-- payment/               # Payment module, responsible for payment processing
    |-- strategies/        # Different payment strategies
    |-- interfaces/
    |-- enums/
    |-- factories/
    |-- payment.module.ts
    `-- payment.service.ts

Implementation Details

Payment Processing

The core of the payment processing logic lies in the use of the Strategy pattern through the PaymentStrategy interface and the PaymentStrategyFactory. When an order is placed, the OrdersController receives the payment provider selected by the customer. It then utilizes PaymentService to process the payment, which, in turn, uses PaymentStrategyFactory to instantiate the appropriate payment strategy based on the customer's choice.

Payment Strategy Factory

This factory encapsulates the logic for instantiating payment strategy objects. It maps each PaymentProvider enum to its corresponding strategy class. When a new payment provider needs to be added, one can simply add a new strategy class and update the factory's mapping without altering the existing consumer code.

Error Handling

Global and local exception filters are used to gracefully handle errors across the application, ensuring that any payment processing errors are caught and handled appropriately.

Running the Project

Installation

1. Clone the repository to the local machine.

2. Ensure the correct version of Node.js is installed, as specified in the .nvmrc file. Switch to the correct version with nvm use, if using NVM.

3. Install required dependencies:

npm install

4. Create .env file. See also .env.example.

5. Then run the application either in production or development mode:

Production Mode

npm run start:prod

Development Mode

  npm run start
  ## or in watch-mode
  npm run start:dev

Running Tests

npm run test

End to End Tests:

npm run test:e2e

Test Coverage

npm run test:cov

Extending the System

To add a new payment provider:

1. Create a new strategy class in src/payment/strategies/ implementing the PaymentStrategy interface.
2. Add the new strategy to the PaymentStrategyFactory mapping.
3. Add the new provider to the PaymentProvider enum.