Cart and Checkout System

A FastAPI-based REST API for managing shopping carts and processing checkouts.

Features

• Create and manage shopping carts
• Add, update, and remove items from carts
• Checkout functionality with payment processing simulation
• SQLite database with SQLAlchemy ORM
• Alembic database migrations
• Automatic API documentation with FastAPI
• CORS support for cross-origin requests

Installation

1. Install dependencies:

pip install -r requirements.txt

2. Run database migrations:

alembic upgrade head

3. Start the application:

uvicorn main:app --reload

The application will be available at http://localhost:8000.

API Documentation

Once the application is running, you can access:

• Interactive API documentation: http://localhost:8000/docs
• Alternative documentation: http://localhost:8000/redoc
• OpenAPI JSON schema: http://localhost:8000/openapi.json

API Endpoints

Cart Management

• POST /api/v1/carts/ - Create a new cart
• GET /api/v1/carts/{cart_id} - Get cart by ID
• GET /api/v1/carts/user/{user_id} - Get all carts for a user
• DELETE /api/v1/carts/{cart_id} - Clear all items from a cart

Cart Items

• POST /api/v1/carts/{cart_id}/items/ - Add item to cart
• PUT /api/v1/carts/{cart_id}/items/{item_id} - Update item quantity
• DELETE /api/v1/carts/{cart_id}/items/{item_id} - Remove item from cart

Checkout

• POST /api/v1/checkout/ - Process checkout

System

• GET / - Service information
• GET /health - Health check endpoint

Example Usage

Create a Cart

curl -X POST "http://localhost:8000/api/v1/carts/" \
     -H "Content-Type: application/json" \
     -d '{"user_id": "user123"}'

Add Item to Cart

curl -X POST "http://localhost:8000/api/v1/carts/1/items/" \
     -H "Content-Type: application/json" \
     -d '{
       "product_id": "prod123",
       "product_name": "Example Product",
       "price": 29.99,
       "quantity": 2
     }'

Checkout

curl -X POST "http://localhost:8000/api/v1/checkout/" \
     -H "Content-Type: application/json" \
     -d '{
       "cart_id": 1,
       "payment_method": "credit_card",
       "billing_address": {
         "street": "123 Main St",
         "city": "Anytown",
         "state": "ST",
         "zip": "12345"
       }
     }'

Database Schema

Carts Table

• id - Primary key
• user_id - User identifier
• status - Cart status (active, checked_out, abandoned)
• created_at - Creation timestamp
• updated_at - Last update timestamp

Cart Items Table

• id - Primary key
• cart_id - Foreign key to carts table
• product_id - Product identifier
• product_name - Product name
• price - Item price
• quantity - Item quantity

Development

Database Migrations

To create a new migration:

alembic revision -m "Description of changes"

To apply migrations:

alembic upgrade head

To rollback migrations:

alembic downgrade -1

Code Linting

The project uses Ruff for code formatting and linting:

ruff check .
ruff format .

Architecture

• FastAPI - Modern Python web framework
• SQLAlchemy - SQL toolkit and ORM
• SQLite - Lightweight database
• Alembic - Database migration tool
• Pydantic - Data validation and serialization