🧾 Invoice Generator

A full-stack Invoice Generator web application built with the MERN Stack (MongoDB, Express, React, Node.js). The application allows users to create invoices, preview them, generate a PDF, and send the invoice directly to a client's email.

This project demonstrates full-stack development including authentication, REST API design, database integration, and email functionality.

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📸 Screenshots

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Table of Contents

• 🧾 Invoice Generator
  • 📸 Screenshots
  • Table of Contents
  • Project Overview
  • Features
    • Authentication
    • Invoice Management
    • Email Functionality
    • User Profile
    • UI
  • Tech Stack
  • Project Structure
  • Prerequisites
  • Installation & Setup
    • 1. Clone the repository
    • 2. Install backend dependencies
    • 3. Install frontend dependencies
    • 4. Configure environment variables
    • 5. Run the backend server
    • 6. Run the frontend application
  • Environment Variables
  • API Endpoints
    • Authentication
    • User Profile
    • Invoices
  • Key Concepts Demonstrated
  • Troubleshooting
  • Future Improvements
  • Contributing
  • Author

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Project Overview

This application allows authenticated users to create professional invoices, preview them, and send them as PDF files directly to clients.

The goal of this project was to build a real-world business tool while demonstrating backend architecture, API development, authentication, and frontend state management.

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Features

Authentication

• User registration
• Secure login using JWT authentication
• Protected routes using middleware

Invoice Management

• Create invoices with multiple line items
• Automatically calculate subtotals, tax, and grand totals
• Edit and update existing invoices
• Preview invoices before sending
• Save invoices to MongoDB

Email Functionality

• Generate invoice as a PDF
• Send invoice directly to client email via Resend
• Custom email message option

User Profile

• Manage user information
• User-specific invoice storage

UI

• Dynamic invoice form with real-time total calculation
• Invoice preview modal
• Clean and responsive interface

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Tech Stack

Layer	Technologies
Frontend	React, TypeScript, Tailwind CSS, Context API
Backend	Node.js, Express.js, JWT Authentication, Resend
Database	MongoDB, Mongoose ODM
Tools	Git, GitHub, Postman, npm

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Project Structure

invoice-generator/
│
├── frontend/
│   ├── api/
│   ├── assets/
│   ├── components/
│   ├── pages/
│   ├── context/
│   └── utils/
│
├── backend/
│   ├── controllers/
│   ├── models/
│   ├── routes/
│   ├── middleware/
│   └── utils/
│
└── README.md

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Prerequisites

Make sure you have the following installed before running the project:

• Node.js v18 or higher
• npm v9 or higher
• [MongoDB]free MongoDB Atlas cluster
• A Gmail account with an App Password enabled (required for Resend)

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Installation & Setup

1. Clone the repository

git clone https://github.com/yourusername/invoice-generator.git
cd invoice-generator

2. Install backend dependencies

cd backend
npm install

3. Install frontend dependencies

cd ../frontend
npm install

4. Configure environment variables

Copy the example env file and fill in your values (see Environment Variables):

cp backend/.env.example backend/.env

5. Run the backend server

From the backend/ directory:

cd ../backend
npm run dev

6. Run the frontend application

Open a new terminal, then from the frontend/ directory:

cd frontend
npm run dev

The frontend will run on http://localhost:5173 and the backend on http://localhost:5000.

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Environment Variables

Create a .env file inside the backend/ folder. An .env.example file is included for reference:

PORT=5000
MONGO_URI=your_mongodb_connection_string
JWT_SECRET=your_jwt_secret
RESEND_API_KEY=your_email@gmail.com
FRONTEND_URL=your_gmail_app_password

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API Endpoints

All protected routes require a valid JWT token passed in the Authorization header:

Authorization: Bearer <token>

Authentication

Method	Endpoint	Auth Required	Description
POST	/api/auth/register	❌	Register a new user
POST	/api/auth/login	❌	Log in and receive a JWT

User Profile

Method	Endpoint	Auth Required	Description
GET	/api/users/profile	✅	Get the current user's profile
PUT	/api/users/profile	✅	Update the current user's profile

Invoices

Method	Endpoint	Auth Required	Description
GET	/api/invoices	✅	Get all invoices for the authenticated user
POST	/api/invoices	✅	Create a new invoice
GET	/api/invoices/:id	✅	Get a single invoice by ID
PUT	/api/invoices/:id	✅	Update an existing invoice
DELETE	/api/invoices/:id	✅	Delete an invoice
POST	/api/invoices/:id/send	✅	Generate PDF and send invoice to client email

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Key Concepts Demonstrated

• Full-stack MERN architecture
• REST API development
• JWT authentication and middleware-protected routes
• MongoDB schema design with Mongoose
• Email service integration with Resend
• PDF generation
• React state management with Context API
• Component-based frontend architecture
• TypeScript for type-safe frontend development

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Troubleshooting

JWT errors / Unauthorized responses

• Make sure JWT_SECRET in your .env matches what was used to sign existing tokens. Changing it invalidates all active sessions.

Emails not sending

• Gmail requires an App Password, not your regular account password. Make sure 2-Step Verification is enabled on your Google account first.
• Check your spam folder if test emails are not arriving.

CORS errors in the browser

• Confirm the backend is running on the expected port and that your Express CORS configuration allows requests from the frontend origin (e.g. http://localhost:5173).

npm run dev not found

• Check that you are in the correct directory (backend/ or frontend/) before running the command.

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Future Improvements

• Invoice dashboard with analytics and charts
• Multiple invoice templates
• Invoice status tracking (Draft / Sent / Paid / Overdue)
• Search and filter invoices

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Contributing

Contributions are welcome! To get started:

1. Fork the repository
2. Create a new branch: git checkout -b feature/your-feature-name
3. Make your changes and commit: git commit -m 'Add some feature'
4. Push to your branch: git push origin feature/your-feature-name
5. Open a Pull Request

Please make sure your code follows the existing style and that any new features are tested before submitting.

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Author

Your Name

• GitHub: @madbag
• LinkedIn: Madhushree B