Invoice Generator API

A simple yet powerful invoice generator that creates professional PDF invoices through a RESTful API with an easy-to-use web interface.

Features

• Generate professional PDF invoices via API or web interface
• Customizable company and client information
• Company logo support
• Multiple invoice templates
• Support for multiple invoice items
• Tax calculation with custom descriptions
• Multiple currency support (USD, EUR, GBP, JPY, CAD, AUD)
• Live total calculation
• Export as PDF or JSON
• Responsive design
• Download generated invoices instantly

Technologies Used

• Backend:

  • Node.js
  • Express.js
  • PDFKit for PDF generation
  • Joi for request validation

• Frontend:

  • HTML5
  • CSS3
  • Vanilla JavaScript

Installation

1. Clone the repository:

git clone https://github.com/T1M00R/invoice-generator-api.git
cd invoice-generator-api

2. Install dependencies:

npm install

3. Create a .env file in the root directory (optional):

PORT=3000

4. Start the development server:

npm run dev

Usage

Web Interface

1. Open your browser and navigate to http://localhost:3000
2. Fill in your company information, including optional logo
3. Enter the client information, invoice details, and add items
4. Set tax rate if applicable
5. Choose an invoice template
6. Select your preferred currency
7. Choose export format (PDF or JSON)
8. Click "Generate Invoice" to create and download the file

API Usage

To generate an invoice programmatically, send a POST request to /api/invoices/pdf or /api/invoices/json with the following JSON structure:

{
  "company": {
    "name": "Your Company Name",
    "logo": "base64EncodedLogoImage"
  },
  "client": {
    "name": "Client Name",
    "address": "123 Client Street, City, Country",
    "email": "client@example.com",
    "phone": "123-456-7890"
  },
  "invoice": {
    "invoiceNumber": "INV-12345",
    "date": "2023-06-01",
    "dueDate": "2023-07-01"
  },
  "items": [
    {
      "description": "Service Description",
      "quantity": 1,
      "unitPrice": 100.00
    }
  ],
  "tax": {
    "rate": 0.1,
    "description": "GST"
  },
  "notes": "Thank you for your business!",
  "template": "classic",
  "currency": "USD"
}

Example using cURL:

curl -X POST \
  http://localhost:3000/api/invoices/pdf \
  -H 'Content-Type: application/json' \
  -d '{
    "company": {
      "name": "Your Company Name"
    },
    "client": {
      "name": "Client Name",
      "address": "123 Client Street, City, Country",
      "email": "client@example.com",
      "phone": "123-456-7890"
    },
    "invoice": {
      "invoiceNumber": "INV-12345",
      "date": "2023-06-01",
      "dueDate": "2023-07-01"
    },
    "items": [
      {
        "description": "Service Description",
        "quantity": 1,
        "unitPrice": 100.00
      }
    ],
    "tax": {
      "rate": 0.1,
      "description": "GST"
    },
    "notes": "Thank you for your business!",
    "template": "classic",
    "currency": "USD"
  }'

Project Structure

invoice-generator-api/
├── frontend/               # Frontend files
│   ├── index.html         # Main HTML file
│   ├── script.js          # Frontend JavaScript
│   └── styles.css         # CSS styles
├── src/                    # Backend source code
│   ├── app.js             # Express application
│   ├── controllers/       # Route controllers
│   │   └── invoiceController.js
│   ├── middleware/        # Express middleware
│   │   └── validator.js
│   ├── routes/            # API routes
│   │   └── invoiceRoutes.js
│   ├── services/          # Business logic
│   │   └── pdfGenerator.js
│   └── utils/             # Utility functions
│       └── errorHandler.js
├── .gitignore             # Git ignore file
├── package.json           # NPM package config
└── README.md              # This file

API Documentation

Generate PDF Invoice

Endpoint: POST /api/invoices/pdf

Content-Type: application/json

Request Body:

Field	Type	Description
company	Object	Your company information
company.name	String	Company name
company.logo	String	Base64 encoded logo (optional)
client	Object	Client information
client.name	String	Client name
client.address	String	Client address
client.email	String	Client email
client.phone	String	Client phone (optional)
invoice	Object	Invoice details
invoice.invoiceNumber	String	Invoice number
invoice.date	String (ISO date)	Invoice date
invoice.dueDate	String (ISO date)	Due date
items	Array	Array of invoice items
items[].description	String	Item description
items[].quantity	Number	Item quantity
items[].unitPrice	Number	Price per unit
tax	Object	Tax information (optional)
tax.rate	Number	Tax rate (0 to 1)
tax.description	String	Tax description
notes	String	Additional notes (optional)
template	String	PDF template (classic, modern, minimal)
currency	String	Currency code (USD, EUR, GBP, JPY, CAD, AUD)

Response:

A PDF file with the generated invoice.

Generate JSON Invoice

Endpoint: POST /api/invoices/json

Content-Type: application/json

Request Body:

Same as for the PDF endpoint.

Response:

A JSON file with the invoice data including calculated totals.

Future Enhancements

• Save invoices to database
• User accounts and authentication
• Recurring invoices
• Email delivery
• Payment integration
• Advanced tax handling
• Invoice tracking and status updates
• Additional currency support

License

ISC

Acknowledgements

• PDFKit for PDF generation
• Express.js for the API framework
• All contributors who help improve this project