Invoice Generation Service

This is a FastAPI application for generating and managing invoices. It allows you to create, read, update, and delete invoices without requiring user signup.

Features

• Generate invoices with automatic invoice number generation
• Store invoice details in SQLite database
• Retrieve invoice information by ID or invoice number
• Update invoice details and status
• Delete invoices
• Web-based user interface for invoice management
• Health check endpoint

Technical Stack

• Framework: FastAPI
• Database: SQLite with SQLAlchemy ORM
• Migrations: Alembic
• Validation: Pydantic
• Frontend: Jinja2 Templates, HTML, CSS, JavaScript
• Linting: Ruff

Project Structure

.
├── alembic.ini               # Alembic configuration file
├── app                       # Application package
│   ├── api                   # API routes
│   │   └── routes            # API route modules
│   │       ├── __init__.py   # Routes initialization
│   │       ├── invoices.py   # Invoice API routes
│   │       └── frontend.py   # Frontend routes
│   ├── core                  # Core functionality
│   │   ├── config.py         # Application settings
│   │   ├── database.py       # Database connection setup
│   │   └── utils.py          # Utility functions
│   ├── models                # SQLAlchemy models
│   │   ├── __init__.py       # Models initialization
│   │   └── invoice.py        # Invoice and InvoiceItem models
│   ├── schemas               # Pydantic schemas
│   │   ├── __init__.py       # Schemas initialization
│   │   └── invoice.py        # Invoice-related schemas
│   ├── static                # Static files
│   │   ├── css               # CSS styles
│   │   │   └── styles.css    # Main stylesheet
│   │   └── js                # JavaScript files
│   │       └── main.js       # Main JavaScript file
│   └── templates             # Jinja2 templates
│       ├── base.html         # Base template with layout
│       ├── home.html         # Home page
│       ├── create_invoice.html # Invoice creation form
│       ├── search_invoice.html # Search for invoices
│       └── invoice_details.html # Invoice details page
├── main.py                   # Application entry point
├── migrations                # Alembic migrations
│   ├── env.py                # Alembic environment
│   ├── script.py.mako        # Migration script template
│   └── versions              # Migration scripts
│       └── ef0aaab3a275_initial_database_tables.py  # Initial migration
├── requirements.txt          # Project dependencies
└── pyproject.toml            # Ruff configuration

API Endpoints

Health Check

• GET /health: Check if the service is running

Invoice Management API

• POST /api/v1/invoices: Create a new invoice
• GET /api/v1/invoices: List all invoices (with pagination)
  • Query parameters:
    • skip: Number of records to skip (default: 0)
    • limit: Maximum number of records to return (default: 100)
    • fields: Comma-separated list of fields to include in the response (e.g., "id,invoice_number,total_amount")
    • status: Filter invoices by status (e.g., "PENDING", "PAID", "CANCELLED")
• GET /api/v1/invoices/{invoice_id}: Get a specific invoice by ID
  • Query parameters:
    • fields: Comma-separated list of fields to include in the response (e.g., "id,invoice_number,total_amount")
• GET /api/v1/invoices/find: Find an invoice by invoice number
  • Query parameters:
    • invoice_number: Invoice number to search for (required)
    • fields: Comma-separated list of fields to include in the response (e.g., "id,invoice_number,total_amount")
• PATCH /api/v1/invoices/{invoice_id}: Update an invoice
• PATCH /api/v1/invoices/{invoice_id}/status: Update invoice status
• DELETE /api/v1/invoices/{invoice_id}: Delete an invoice

Frontend Routes

• GET /: Home page with list of recent invoices
• GET /create: Form to create a new invoice
• POST /create: Process invoice creation form
• GET /search: Form to search for invoices by number
• POST /search: Process invoice search
• GET /invoice/{invoice_id}: View invoice details
• POST /invoice/{invoice_id}/status: Update invoice status

Setup and Installation

1. Clone the repository
2. Install dependencies:

   pip install -r requirements.txt
   

3. Run migrations:

   alembic upgrade head
   

4. Start the application:

   uvicorn main:app --reload
   

API Documentation

Once the application is running, you can access:

• Interactive API documentation at /docs (Swagger UI)
• Alternative API documentation at /redoc (ReDoc)

Web Interface

The application comes with a full web interface that allows users to:

• View a list of recent invoices on the home page
• Create new invoices using a dynamic form
• Search for existing invoices by invoice number
• View detailed invoice information
• Update invoice status (PENDING, PAID, CANCELLED)
• Print invoices

Invoice Number Format

Invoices are automatically assigned a unique invoice number with the format:

• INV-YYYYMM-XXXXXX, where:
  • INV is a fixed prefix
  • YYYYMM is the year and month (e.g., 202307 for July 2023)
  • XXXXXX is a random alphanumeric string

Query Parameters

Field Filtering

The API supports field filtering for GET operations. This allows clients to request only the specific fields they need, which can improve performance and reduce bandwidth usage.

How to Use Field Filtering:

1. Add a fields query parameter to GET requests
2. Specify a comma-separated list of field names to include in the response

Example:

To get only the ID, invoice number, and total amount of invoices:

GET /api/v1/invoices?fields=id,invoice_number,total_amount

This would return:

[
  {
    "id": 1,
    "invoice_number": "INV-202307-A1B2C3",
    "total_amount": 100.0
  },
  {
    "id": 2,
    "invoice_number": "INV-202307-D4E5F6",
    "total_amount": 200.0
  }
]

Status Filtering

The API supports filtering invoices by their status (PENDING, PAID, CANCELLED).

How to Use Status Filtering:

1. Add a status query parameter to the GET request
2. Specify one of the allowed status values: "PENDING", "PAID", or "CANCELLED"

Example:

To get only paid invoices:

GET /api/v1/invoices?status=PAID

To combine with other parameters:

GET /api/v1/invoices?status=PENDING&fields=id,invoice_number,total_amount&limit=5

Available Fields:

Invoices have the following fields that can be filtered:

• id
• invoice_number
• date_created
• due_date
• total_amount
• status
• customer_name
• customer_email
• customer_address
• notes
• items (this includes related invoice items)