SaaS Invoicing Application

A comprehensive SaaS invoicing application built with FastAPI and SQLite, designed for businesses to manage organizations, clients, and invoices efficiently.

Features

• Multi-tenant Architecture: Supports multiple organizations with user management
• User Authentication: Secure JWT-based authentication and role-based permissions
• Organization Management: Create and manage organizations with detailed information
• Client Management: Maintain a database of clients for each organization
• Invoice Management: Create, update, and delete invoices with line items
• PDF Generation: Generate professional PDF invoices for sharing with clients
• API Documentation: Interactive API documentation with Swagger UI and ReDoc

Prerequisites

• Python 3.8+
• pip (Python package manager)

Environment Variables

The application uses the following environment variables:

Variable	Description	Default Value
SECRET_KEY	Secret key for JWT token generation	CHANGE_ME_TO_A_SECURE_RANDOM_STRING
ACCESS_TOKEN_EXPIRE_MINUTES	Access token expiration time in minutes	30
SERVER_HOST	Host URL for the server	http://localhost:8000

Installation

1. Clone the repository:

git clone https://github.com/yourusername/saasinvoicingapplication.git
cd saasinvoicingapplication

2. Create a virtual environment (optional but recommended):

python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

3. Install dependencies:

pip install -r requirements.txt

4. Create a .env file with your environment variables:

SECRET_KEY=your-secure-secret-key
ACCESS_TOKEN_EXPIRE_MINUTES=30
SERVER_HOST=http://localhost:8000

5. Initialize the database:

mkdir -p /app/storage/db
python -c "from app.db.base import Base; from app.db.session import engine; Base.metadata.create_all(bind=engine)"
alembic upgrade head

Running the Application

Start the application using uvicorn:

uvicorn main:app --host 0.0.0.0 --port 8000 --reload

The API will be available at:

• API: http://localhost:8000
• Swagger UI Documentation: http://localhost:8000/docs
• ReDoc Documentation: http://localhost:8000/redoc

API Structure

The API follows a RESTful design and is structured as follows:

Authentication Endpoints

• POST /api/v1/auth/token - Get access token
• POST /api/v1/auth/test-token - Test token validity

User Management

• GET /api/v1/users/ - List users (admin only)
• POST /api/v1/users/ - Create user (admin only)
• GET /api/v1/users/me - Get current user info
• PUT /api/v1/users/me - Update current user
• GET /api/v1/users/{user_id} - Get user by ID
• PUT /api/v1/users/{user_id} - Update user (admin only)

Organization Management

• GET /api/v1/organizations/ - List organizations
• POST /api/v1/organizations/ - Create organization (admin only)
• GET /api/v1/organizations/{id} - Get organization by ID
• PUT /api/v1/organizations/{id} - Update organization
• DELETE /api/v1/organizations/{id} - Delete organization (admin only)

Client Management

• GET /api/v1/clients/ - List clients
• POST /api/v1/clients/ - Create client
• GET /api/v1/clients/{id} - Get client by ID
• PUT /api/v1/clients/{id} - Update client
• DELETE /api/v1/clients/{id} - Delete client

Invoice Management

• GET /api/v1/invoices/ - List invoices
• POST /api/v1/invoices/ - Create invoice
• GET /api/v1/invoices/{id} - Get invoice by ID
• PUT /api/v1/invoices/{id} - Update invoice
• DELETE /api/v1/invoices/{id} - Delete invoice
• GET /api/v1/invoices/{id}/pdf - Generate PDF for invoice

Data Models

User

• id: Unique identifier
• email: Email address (unique)
• full_name: Full name
• hashed_password: Hashed password
• is_active: User status
• is_superuser: Admin status
• organization_id: Associated organization

Organization

• id: Unique identifier
• name: Organization name
• address, city, state, postal_code, country: Address information
• phone, email, website: Contact information
• tax_id: Tax identification number
• logo_url: URL to organization logo

Client

• id: Unique identifier
• name: Client name
• contact_name: Primary contact
• email, phone: Contact information
• address, city, state, postal_code, country: Address information
• tax_id: Tax identification number
• notes: Additional notes
• organization_id: Associated organization
• created_by_id: User who created the client

Invoice

• id: Unique identifier
• invoice_number: Invoice reference number
• status: Invoice status (draft, sent, paid, overdue, cancelled)
• issue_date, due_date: Invoice dates
• subtotal, tax_rate, tax_amount, discount, total: Financial information
• notes, terms: Additional information
• is_recurring, recurring_interval: Recurring invoice details
• client_id: Associated client
• organization_id: Associated organization
• created_by_id: User who created the invoice

InvoiceItem

• id: Unique identifier
• description: Item description
• quantity, unit_price, amount: Item details
• invoice_id: Associated invoice

Development

Running Tests

Run tests using pytest:

pytest

Database Migrations

Generate a new migration after model changes:

alembic revision --autogenerate -m "Description of changes"

Apply migrations:

alembic upgrade head

License

This project is licensed under the MIT License - see the LICENSE file for details.