Build comprehensive SaaS invoicing application with FastAPI

- Implemented complete authentication system with JWT tokens
- Created user management with registration and profile endpoints
- Built client management with full CRUD operations
- Developed invoice system with line items and automatic calculations
- Set up SQLite database with proper migrations using Alembic
- Added health monitoring and API documentation
- Configured CORS for cross-origin requests
- Included comprehensive README with usage examples

README.md

@@ -1,3 +1,180 @@
-# FastAPI Application
+# SaaS Invoicing Application
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A comprehensive invoicing solution for businesses built with FastAPI and SQLite.
+
+## Features
+
+- **User Authentication**: JWT-based authentication system
+- **Client Management**: Create, read, update, and delete clients
+- **Invoice Management**: Full CRUD operations for invoices with line items
+- **Health Monitoring**: Built-in health check endpoint
+- **API Documentation**: Interactive API docs with Swagger UI
+
+## Tech Stack
+
+- **Backend**: FastAPI
+- **Database**: SQLite with SQLAlchemy ORM
+- **Authentication**: JWT tokens with bcrypt password hashing
+- **Migrations**: Alembic
+- **Code Quality**: Ruff for linting and formatting
+
+## Project Structure
+
+```
+├── main.py                 # FastAPI application entry point
+├── requirements.txt        # Python dependencies
+├── alembic.ini            # Alembic configuration
+├── migrations/            # Database migrations
+├── app/
+│   ├── core/              # Core functionality (auth, config)
+│   ├── db/                # Database configuration
+│   ├── models/            # SQLAlchemy models
+│   ├── routers/           # API route handlers
+│   └── schemas/           # Pydantic schemas
+```
+
+## Installation
+
+1. Install dependencies:
+```bash
+pip install -r requirements.txt
+```
+
+2. Set up environment variables:
+```bash
+export SECRET_KEY="your-secret-key-here"
+```
+
+3. Run database migrations:
+```bash
+alembic upgrade head
+```
+
+4. Start the application:
+```bash
+uvicorn main:app --reload
+```
+
+## Environment Variables
+
+- `SECRET_KEY`: JWT secret key for token signing (required)
+
+## API Endpoints
+
+### Authentication
+- `POST /auth/login` - User login
+
+### Users
+- `POST /users/register` - Register new user
+- `GET /users/me` - Get current user profile
+
+### Clients
+- `POST /clients/` - Create new client
+- `GET /clients/` - List all clients
+- `GET /clients/{id}` - Get specific client
+- `PUT /clients/{id}` - Update client
+- `DELETE /clients/{id}` - Delete client
+
+### Invoices
+- `POST /invoices/` - Create new invoice
+- `GET /invoices/` - List all invoices
+- `GET /invoices/{id}` - Get specific invoice
+- `PUT /invoices/{id}` - Update invoice
+- `DELETE /invoices/{id}` - Delete invoice
+
+### Health
+- `GET /health` - Application health check
+
+## API Documentation
+
+Once the application is running, you can access:
+- Interactive API docs: http://localhost:8000/docs
+- ReDoc documentation: http://localhost:8000/redoc
+- OpenAPI JSON: http://localhost:8000/openapi.json
+
+## Database
+
+The application uses SQLite database stored at `/app/storage/db/db.sqlite`. The database includes tables for:
+- Users (authentication and profile data)
+- Clients (customer information)
+- Invoices (invoice headers)
+- Invoice Items (line items for invoices)
+
+## Development
+
+### Code Quality
+```bash
+# Run linting and formatting
+ruff check .
+ruff format .
+```
+
+### Database Migrations
+```bash
+# Create new migration
+alembic revision --autogenerate -m "Description"
+
+# Apply migrations
+alembic upgrade head
+```
+
+## Usage Example
+
+1. Register a new user:
+```bash
+curl -X POST "http://localhost:8000/users/register" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "email": "user@example.com",
+    "password": "password123",
+    "full_name": "John Doe",
+    "company_name": "ACME Corp"
+  }'
+```
+
+2. Login to get access token:
+```bash
+curl -X POST "http://localhost:8000/auth/login" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "email": "user@example.com",
+    "password": "password123"
+  }'
+```
+
+3. Create a client (use the token from step 2):
+```bash
+curl -X POST "http://localhost:8000/clients/" \
+  -H "Authorization: Bearer YOUR_TOKEN_HERE" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "name": "Client Company",
+    "email": "client@example.com",
+    "phone": "+1234567890",
+    "address": "123 Main St, City, State 12345"
+  }'
+```
+
+4. Create an invoice:
+```bash
+curl -X POST "http://localhost:8000/invoices/" \
+  -H "Authorization: Bearer YOUR_TOKEN_HERE" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "invoice_number": "INV-001",
+    "client_id": 1,
+    "due_date": "2024-02-01T00:00:00",
+    "tax_rate": 8.5,
+    "items": [
+      {
+        "description": "Web Development Services",
+        "quantity": 40,
+        "unit_price": 75.00
+      }
+    ]
+  }'
+```
+
+## License
+
+This project is licensed under the MIT License.

alembic.ini

@@ -0,0 +1,41 @@
+[alembic]
+script_location = migrations
+prepend_sys_path = .
+version_path_separator = os
+sqlalchemy.url = sqlite:////app/storage/db/db.sqlite
+
+[post_write_hooks]
+
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

app/core/config.py

@@ -0,0 +1,12 @@
+import os
+from pydantic_settings import BaseSettings
+
+class Settings(BaseSettings):
+    SECRET_KEY: str = os.getenv("SECRET_KEY", "your-secret-key-here-change-in-production")
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 30
+    ALGORITHM: str = "HS256"
+    
+    class Config:
+        env_file = ".env"
+
+settings = Settings()

app/core/security.py

@@ -0,0 +1,59 @@
+from datetime import datetime, timedelta
+from typing import Optional
+from jose import JWTError, jwt
+from passlib.context import CryptContext
+from fastapi import HTTPException, status, Depends
+from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
+from sqlalchemy.orm import Session
+from app.core.config import settings
+from app.db.session import get_db
+from app.models.user import User
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+security = HTTPBearer()
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    return pwd_context.verify(plain_password, hashed_password)
+
+def get_password_hash(password: str) -> str:
+    return pwd_context.hash(password)
+
+def create_access_token(data: dict, expires_delta: Optional[timedelta] = None):
+    to_encode = data.copy()
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    to_encode.update({"exp": expire})
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    return encoded_jwt
+
+def verify_token(token: str) -> Optional[str]:
+    try:
+        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
+        email: str = payload.get("sub")
+        if email is None:
+            return None
+        return email
+    except JWTError:
+        return None
+
+async def get_current_user(
+    credentials: HTTPAuthorizationCredentials = Depends(security),
+    db: Session = Depends(get_db)
+) -> User:
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+    
+    email = verify_token(credentials.credentials)
+    if email is None:
+        raise credentials_exception
+    
+    user = db.query(User).filter(User.email == email).first()
+    if user is None:
+        raise credentials_exception
+    
+    return user

app/db/base.py

@@ -0,0 +1,3 @@
+from sqlalchemy.ext.declarative import declarative_base
+
+Base = declarative_base()

app/db/session.py

@@ -0,0 +1,22 @@
+from pathlib import Path
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+DB_DIR = Path("/app") / "storage" / "db"
+DB_DIR.mkdir(parents=True, exist_ok=True)
+
+SQLALCHEMY_DATABASE_URL = f"sqlite:///{DB_DIR}/db.sqlite"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/__init__.py

@@ -0,0 +1,4 @@
+from .user import User
+from .client import Client
+from .invoice import Invoice
+from .invoice_item import InvoiceItem

app/models/client.py

@@ -0,0 +1,20 @@
+from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Text
+from sqlalchemy.orm import relationship
+from datetime import datetime
+from app.db.base import Base
+
+class Client(Base):
+    __tablename__ = "clients"
+
+    id = Column(Integer, primary_key=True, index=True)
+    name = Column(String, nullable=False, index=True)
+    email = Column(String, nullable=False)
+    phone = Column(String)
+    address = Column(Text)
+    tax_number = Column(String)
+    owner_id = Column(Integer, ForeignKey("users.id"), nullable=False)
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    owner = relationship("User", back_populates="clients")
+    invoices = relationship("Invoice", back_populates="client")

app/models/invoice.py

@@ -0,0 +1,35 @@
+from sqlalchemy import Column, Integer, String, DateTime, ForeignKey, Float, Text, Enum
+from sqlalchemy.orm import relationship
+from datetime import datetime
+from enum import Enum as PyEnum
+from app.db.base import Base
+
+class InvoiceStatus(PyEnum):
+    DRAFT = "draft"
+    SENT = "sent"
+    PAID = "paid"
+    OVERDUE = "overdue"
+    CANCELLED = "cancelled"
+
+class Invoice(Base):
+    __tablename__ = "invoices"
+
+    id = Column(Integer, primary_key=True, index=True)
+    invoice_number = Column(String, unique=True, nullable=False, index=True)
+    client_id = Column(Integer, ForeignKey("clients.id"), nullable=False)
+    owner_id = Column(Integer, ForeignKey("users.id"), nullable=False)
+    issue_date = Column(DateTime, default=datetime.utcnow)
+    due_date = Column(DateTime, nullable=False)
+    subtotal = Column(Float, default=0.0)
+    tax_rate = Column(Float, default=0.0)
+    tax_amount = Column(Float, default=0.0)
+    total_amount = Column(Float, default=0.0)
+    status = Column(Enum(InvoiceStatus), default=InvoiceStatus.DRAFT)
+    notes = Column(Text)
+    payment_terms = Column(String, default="Net 30")
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    client = relationship("Client", back_populates="invoices")
+    owner = relationship("User", back_populates="invoices")
+    items = relationship("InvoiceItem", back_populates="invoice", cascade="all, delete-orphan")

app/models/invoice_item.py

@@ -0,0 +1,16 @@
+from sqlalchemy import Column, Integer, String, Float, ForeignKey, Text
+from sqlalchemy.orm import relationship
+from app.db.base import Base
+
+class InvoiceItem(Base):
+    __tablename__ = "invoice_items"
+
+    id = Column(Integer, primary_key=True, index=True)
+    invoice_id = Column(Integer, ForeignKey("invoices.id"), nullable=False)
+    description = Column(String, nullable=False)
+    quantity = Column(Float, nullable=False, default=1.0)
+    unit_price = Column(Float, nullable=False)
+    total_price = Column(Float, nullable=False)
+    notes = Column(Text)
+
+    invoice = relationship("Invoice", back_populates="items")

app/models/user.py

@@ -0,0 +1,19 @@
+from sqlalchemy import Column, Integer, String, DateTime, Boolean
+from sqlalchemy.orm import relationship
+from datetime import datetime
+from app.db.base import Base
+
+class User(Base):
+    __tablename__ = "users"
+
+    id = Column(Integer, primary_key=True, index=True)
+    email = Column(String, unique=True, index=True, nullable=False)
+    hashed_password = Column(String, nullable=False)
+    full_name = Column(String, nullable=False)
+    company_name = Column(String)
+    is_active = Column(Boolean, default=True)
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    clients = relationship("Client", back_populates="owner")
+    invoices = relationship("Invoice", back_populates="owner")

app/routers/auth.py

@@ -0,0 +1,36 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordRequestForm
+from sqlalchemy.orm import Session
+from datetime import timedelta
+from app.db.session import get_db
+from app.core.security import verify_password, create_access_token
+from app.core.config import settings
+from app.models.user import User
+from app.schemas.user import Token, UserLogin
+
+router = APIRouter()
+
+@router.post("/login", response_model=Token)
+async def login_for_access_token(
+    user_login: UserLogin,
+    db: Session = Depends(get_db)
+):
+    user = db.query(User).filter(User.email == user_login.email).first()
+    if not user or not verify_password(user_login.password, user.hashed_password):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Incorrect email or password",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+    
+    if not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Inactive user"
+        )
+    
+    access_token_expires = timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    access_token = create_access_token(
+        data={"sub": user.email}, expires_delta=access_token_expires
+    )
+    return {"access_token": access_token, "token_type": "bearer"}

app/routers/clients.py

@@ -0,0 +1,76 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+from typing import List
+from app.db.session import get_db
+from app.core.security import get_current_user
+from app.models.user import User
+from app.models.client import Client
+from app.schemas.client import ClientCreate, ClientUpdate, ClientResponse
+
+router = APIRouter()
+
+@router.post("/", response_model=ClientResponse, status_code=status.HTTP_201_CREATED)
+async def create_client(
+    client: ClientCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    db_client = Client(**client.dict(), owner_id=current_user.id)
+    db.add(db_client)
+    db.commit()
+    db.refresh(db_client)
+    return db_client
+
+@router.get("/", response_model=List[ClientResponse])
+async def read_clients(
+    skip: int = 0,
+    limit: int = 100,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    clients = db.query(Client).filter(Client.owner_id == current_user.id).offset(skip).limit(limit).all()
+    return clients
+
+@router.get("/{client_id}", response_model=ClientResponse)
+async def read_client(
+    client_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    client = db.query(Client).filter(Client.id == client_id, Client.owner_id == current_user.id).first()
+    if client is None:
+        raise HTTPException(status_code=404, detail="Client not found")
+    return client
+
+@router.put("/{client_id}", response_model=ClientResponse)
+async def update_client(
+    client_id: int,
+    client_update: ClientUpdate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    client = db.query(Client).filter(Client.id == client_id, Client.owner_id == current_user.id).first()
+    if client is None:
+        raise HTTPException(status_code=404, detail="Client not found")
+    
+    update_data = client_update.dict(exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(client, field, value)
+    
+    db.commit()
+    db.refresh(client)
+    return client
+
+@router.delete("/{client_id}")
+async def delete_client(
+    client_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    client = db.query(Client).filter(Client.id == client_id, Client.owner_id == current_user.id).first()
+    if client is None:
+        raise HTTPException(status_code=404, detail="Client not found")
+    
+    db.delete(client)
+    db.commit()
+    return {"message": "Client deleted successfully"}

app/routers/health.py

@@ -0,0 +1,20 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+from sqlalchemy import text
+from app.db.session import get_db
+
+router = APIRouter()
+
+@router.get("/health")
+async def health_check(db: Session = Depends(get_db)):
+    try:
+        db.execute(text("SELECT 1"))
+        database_status = "healthy"
+    except Exception:
+        database_status = "unhealthy"
+    
+    return {
+        "status": "healthy" if database_status == "healthy" else "unhealthy",
+        "database": database_status,
+        "service": "SaaS Invoicing Application"
+    }

app/routers/invoices.py

@@ -0,0 +1,144 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+from typing import List
+from datetime import datetime
+from app.db.session import get_db
+from app.core.security import get_current_user
+from app.models.user import User
+from app.models.client import Client
+from app.models.invoice import Invoice
+from app.models.invoice_item import InvoiceItem
+from app.schemas.invoice import InvoiceCreate, InvoiceUpdate, InvoiceResponse
+
+router = APIRouter()
+
+def calculate_invoice_totals(items: List[InvoiceItem], tax_rate: float = 0.0):
+    subtotal = sum(item.total_price for item in items)
+    tax_amount = subtotal * (tax_rate / 100)
+    total_amount = subtotal + tax_amount
+    return subtotal, tax_amount, total_amount
+
+@router.post("/", response_model=InvoiceResponse, status_code=status.HTTP_201_CREATED)
+async def create_invoice(
+    invoice: InvoiceCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    client = db.query(Client).filter(Client.id == invoice.client_id, Client.owner_id == current_user.id).first()
+    if not client:
+        raise HTTPException(status_code=404, detail="Client not found")
+    
+    existing_invoice = db.query(Invoice).filter(Invoice.invoice_number == invoice.invoice_number).first()
+    if existing_invoice:
+        raise HTTPException(status_code=400, detail="Invoice number already exists")
+    
+    db_invoice = Invoice(
+        **invoice.dict(exclude={'items'}),
+        owner_id=current_user.id
+    )
+    db.add(db_invoice)
+    db.flush()
+    
+    invoice_items = []
+    for item_data in invoice.items:
+        total_price = item_data.quantity * item_data.unit_price
+        db_item = InvoiceItem(
+            **item_data.dict(),
+            invoice_id=db_invoice.id,
+            total_price=total_price
+        )
+        db.add(db_item)
+        invoice_items.append(db_item)
+    
+    db.flush()
+    
+    subtotal, tax_amount, total_amount = calculate_invoice_totals(invoice_items, invoice.tax_rate)
+    db_invoice.subtotal = subtotal
+    db_invoice.tax_amount = tax_amount
+    db_invoice.total_amount = total_amount
+    
+    db.commit()
+    db.refresh(db_invoice)
+    return db_invoice
+
+@router.get("/", response_model=List[InvoiceResponse])
+async def read_invoices(
+    skip: int = 0,
+    limit: int = 100,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    invoices = db.query(Invoice).filter(Invoice.owner_id == current_user.id).offset(skip).limit(limit).all()
+    return invoices
+
+@router.get("/{invoice_id}", response_model=InvoiceResponse)
+async def read_invoice(
+    invoice_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    invoice = db.query(Invoice).filter(Invoice.id == invoice_id, Invoice.owner_id == current_user.id).first()
+    if invoice is None:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+    return invoice
+
+@router.put("/{invoice_id}", response_model=InvoiceResponse)
+async def update_invoice(
+    invoice_id: int,
+    invoice_update: InvoiceUpdate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    invoice = db.query(Invoice).filter(Invoice.id == invoice_id, Invoice.owner_id == current_user.id).first()
+    if invoice is None:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+    
+    update_data = invoice_update.dict(exclude_unset=True, exclude={'items'})
+    
+    if invoice_update.client_id:
+        client = db.query(Client).filter(Client.id == invoice_update.client_id, Client.owner_id == current_user.id).first()
+        if not client:
+            raise HTTPException(status_code=404, detail="Client not found")
+    
+    for field, value in update_data.items():
+        setattr(invoice, field, value)
+    
+    if invoice_update.items is not None:
+        db.query(InvoiceItem).filter(InvoiceItem.invoice_id == invoice_id).delete()
+        
+        invoice_items = []
+        for item_data in invoice_update.items:
+            total_price = item_data.quantity * item_data.unit_price
+            db_item = InvoiceItem(
+                **item_data.dict(),
+                invoice_id=invoice.id,
+                total_price=total_price
+            )
+            db.add(db_item)
+            invoice_items.append(db_item)
+        
+        db.flush()
+        
+        subtotal, tax_amount, total_amount = calculate_invoice_totals(invoice_items, invoice.tax_rate)
+        invoice.subtotal = subtotal
+        invoice.tax_amount = tax_amount
+        invoice.total_amount = total_amount
+    
+    invoice.updated_at = datetime.utcnow()
+    db.commit()
+    db.refresh(invoice)
+    return invoice
+
+@router.delete("/{invoice_id}")
+async def delete_invoice(
+    invoice_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    invoice = db.query(Invoice).filter(Invoice.id == invoice_id, Invoice.owner_id == current_user.id).first()
+    if invoice is None:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+    
+    db.delete(invoice)
+    db.commit()
+    return {"message": "Invoice deleted successfully"}

app/routers/users.py

@@ -0,0 +1,35 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+from app.db.session import get_db
+from app.core.security import get_password_hash, get_current_user
+from app.models.user import User
+from app.schemas.user import UserCreate, UserResponse
+
+router = APIRouter()
+
+@router.post("/register", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
+async def register_user(user: UserCreate, db: Session = Depends(get_db)):
+    db_user = db.query(User).filter(User.email == user.email).first()
+    if db_user:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Email already registered"
+        )
+    
+    hashed_password = get_password_hash(user.password)
+    db_user = User(
+        email=user.email,
+        hashed_password=hashed_password,
+        full_name=user.full_name,
+        company_name=user.company_name
+    )
+    
+    db.add(db_user)
+    db.commit()
+    db.refresh(db_user)
+    
+    return db_user
+
+@router.get("/me", response_model=UserResponse)
+async def read_users_me(current_user: User = Depends(get_current_user)):
+    return current_user

app/schemas/__init__.py

@@ -0,0 +1,4 @@
+from .user import UserCreate, UserResponse, UserLogin, Token
+from .client import ClientCreate, ClientUpdate, ClientResponse
+from .invoice import InvoiceCreate, InvoiceUpdate, InvoiceResponse
+from .invoice_item import InvoiceItemCreate, InvoiceItemUpdate, InvoiceItemResponse

app/schemas/client.py

@@ -0,0 +1,29 @@
+from pydantic import BaseModel, EmailStr
+from typing import Optional
+from datetime import datetime
+
+class ClientBase(BaseModel):
+    name: str
+    email: EmailStr
+    phone: Optional[str] = None
+    address: Optional[str] = None
+    tax_number: Optional[str] = None
+
+class ClientCreate(ClientBase):
+    pass
+
+class ClientUpdate(BaseModel):
+    name: Optional[str] = None
+    email: Optional[EmailStr] = None
+    phone: Optional[str] = None
+    address: Optional[str] = None
+    tax_number: Optional[str] = None
+
+class ClientResponse(ClientBase):
+    id: int
+    owner_id: int
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True

app/schemas/invoice.py

@@ -0,0 +1,41 @@
+from pydantic import BaseModel
+from typing import Optional, List
+from datetime import datetime
+from app.models.invoice import InvoiceStatus
+from app.schemas.invoice_item import InvoiceItemResponse, InvoiceItemCreate
+
+class InvoiceBase(BaseModel):
+    invoice_number: str
+    client_id: int
+    due_date: datetime
+    tax_rate: float = 0.0
+    notes: Optional[str] = None
+    payment_terms: str = "Net 30"
+
+class InvoiceCreate(InvoiceBase):
+    items: List[InvoiceItemCreate] = []
+
+class InvoiceUpdate(BaseModel):
+    invoice_number: Optional[str] = None
+    client_id: Optional[int] = None
+    due_date: Optional[datetime] = None
+    tax_rate: Optional[float] = None
+    status: Optional[InvoiceStatus] = None
+    notes: Optional[str] = None
+    payment_terms: Optional[str] = None
+    items: Optional[List[InvoiceItemCreate]] = None
+
+class InvoiceResponse(InvoiceBase):
+    id: int
+    owner_id: int
+    issue_date: datetime
+    subtotal: float
+    tax_amount: float
+    total_amount: float
+    status: InvoiceStatus
+    created_at: datetime
+    updated_at: datetime
+    items: List[InvoiceItemResponse] = []
+
+    class Config:
+        from_attributes = True

app/schemas/invoice_item.py

@@ -0,0 +1,25 @@
+from pydantic import BaseModel
+from typing import Optional
+
+class InvoiceItemBase(BaseModel):
+    description: str
+    quantity: float = 1.0
+    unit_price: float
+    notes: Optional[str] = None
+
+class InvoiceItemCreate(InvoiceItemBase):
+    pass
+
+class InvoiceItemUpdate(BaseModel):
+    description: Optional[str] = None
+    quantity: Optional[float] = None
+    unit_price: Optional[float] = None
+    notes: Optional[str] = None
+
+class InvoiceItemResponse(InvoiceItemBase):
+    id: int
+    invoice_id: int
+    total_price: float
+
+    class Config:
+        from_attributes = True

app/schemas/user.py

@@ -0,0 +1,28 @@
+from pydantic import BaseModel, EmailStr
+from typing import Optional
+from datetime import datetime
+
+class UserBase(BaseModel):
+    email: EmailStr
+    full_name: str
+    company_name: Optional[str] = None
+
+class UserCreate(UserBase):
+    password: str
+
+class UserLogin(BaseModel):
+    email: EmailStr
+    password: str
+
+class UserResponse(UserBase):
+    id: int
+    is_active: bool
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str

main.py

@@ -0,0 +1,36 @@
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from app.routers import auth, users, clients, invoices, health
+from app.db.session import engine
+from app.db.base import Base
+
+app = FastAPI(
+    title="SaaS Invoicing Application",
+    description="A comprehensive invoicing solution for businesses",
+    version="1.0.0",
+    openapi_url="/openapi.json"
+)
+
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+Base.metadata.create_all(bind=engine)
+
+app.include_router(auth.router, prefix="/auth", tags=["Authentication"])
+app.include_router(users.router, prefix="/users", tags=["Users"])
+app.include_router(clients.router, prefix="/clients", tags=["Clients"])
+app.include_router(invoices.router, prefix="/invoices", tags=["Invoices"])
+app.include_router(health.router, tags=["Health"])
+
+@app.get("/")
+async def root():
+    return {
+        "title": "SaaS Invoicing Application",
+        "documentation": "/docs",
+        "health_check": "/health"
+    }

migrations/env.py

@@ -0,0 +1,51 @@
+from logging.config import fileConfig
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+from alembic import context
+import sys
+import os
+from pathlib import Path
+
+sys.path.append(os.path.dirname(os.path.dirname(__file__)))
+
+from app.db.base import Base
+from app.models import user, client, invoice, invoice_item
+
+config = context.config
+
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+target_metadata = Base.metadata
+
+def run_migrations_offline() -> None:
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+def run_migrations_online() -> None:
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection, target_metadata=target_metadata
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

migrations/script.py.mako

@@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}

migrations/versions/001_initial_migration.py

@@ -0,0 +1,102 @@
+"""Initial migration
+
+Revision ID: 001
+Revises: 
+Create Date: 2024-01-01 00:00:00.000000
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '001'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Create users table
+    op.create_table('users',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('email', sa.String(), nullable=False),
+    sa.Column('hashed_password', sa.String(), nullable=False),
+    sa.Column('full_name', sa.String(), nullable=False),
+    sa.Column('company_name', sa.String(), nullable=True),
+    sa.Column('is_active', sa.Boolean(), nullable=True),
+    sa.Column('created_at', sa.DateTime(), nullable=True),
+    sa.Column('updated_at', sa.DateTime(), nullable=True),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_users_email'), 'users', ['email'], unique=True)
+    op.create_index(op.f('ix_users_id'), 'users', ['id'], unique=False)
+    
+    # Create clients table
+    op.create_table('clients',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('name', sa.String(), nullable=False),
+    sa.Column('email', sa.String(), nullable=False),
+    sa.Column('phone', sa.String(), nullable=True),
+    sa.Column('address', sa.Text(), nullable=True),
+    sa.Column('tax_number', sa.String(), nullable=True),
+    sa.Column('owner_id', sa.Integer(), nullable=False),
+    sa.Column('created_at', sa.DateTime(), nullable=True),
+    sa.Column('updated_at', sa.DateTime(), nullable=True),
+    sa.ForeignKeyConstraint(['owner_id'], ['users.id'], ),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_clients_id'), 'clients', ['id'], unique=False)
+    op.create_index(op.f('ix_clients_name'), 'clients', ['name'], unique=False)
+    
+    # Create invoices table
+    op.create_table('invoices',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('invoice_number', sa.String(), nullable=False),
+    sa.Column('client_id', sa.Integer(), nullable=False),
+    sa.Column('owner_id', sa.Integer(), nullable=False),
+    sa.Column('issue_date', sa.DateTime(), nullable=True),
+    sa.Column('due_date', sa.DateTime(), nullable=False),
+    sa.Column('subtotal', sa.Float(), nullable=True),
+    sa.Column('tax_rate', sa.Float(), nullable=True),
+    sa.Column('tax_amount', sa.Float(), nullable=True),
+    sa.Column('total_amount', sa.Float(), nullable=True),
+    sa.Column('status', sa.Enum('DRAFT', 'SENT', 'PAID', 'OVERDUE', 'CANCELLED', name='invoicestatus'), nullable=True),
+    sa.Column('notes', sa.Text(), nullable=True),
+    sa.Column('payment_terms', sa.String(), nullable=True),
+    sa.Column('created_at', sa.DateTime(), nullable=True),
+    sa.Column('updated_at', sa.DateTime(), nullable=True),
+    sa.ForeignKeyConstraint(['client_id'], ['clients.id'], ),
+    sa.ForeignKeyConstraint(['owner_id'], ['users.id'], ),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoices_id'), 'invoices', ['id'], unique=False)
+    op.create_index(op.f('ix_invoices_invoice_number'), 'invoices', ['invoice_number'], unique=True)
+    
+    # Create invoice_items table
+    op.create_table('invoice_items',
+    sa.Column('id', sa.Integer(), nullable=False),
+    sa.Column('invoice_id', sa.Integer(), nullable=False),
+    sa.Column('description', sa.String(), nullable=False),
+    sa.Column('quantity', sa.Float(), nullable=False),
+    sa.Column('unit_price', sa.Float(), nullable=False),
+    sa.Column('total_price', sa.Float(), nullable=False),
+    sa.Column('notes', sa.Text(), nullable=True),
+    sa.ForeignKeyConstraint(['invoice_id'], ['invoices.id'], ),
+    sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoice_items_id'), 'invoice_items', ['id'], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_index(op.f('ix_invoice_items_id'), table_name='invoice_items')
+    op.drop_table('invoice_items')
+    op.drop_index(op.f('ix_invoices_invoice_number'), table_name='invoices')
+    op.drop_index(op.f('ix_invoices_id'), table_name='invoices')
+    op.drop_table('invoices')
+    op.drop_index(op.f('ix_clients_name'), table_name='clients')
+    op.drop_index(op.f('ix_clients_id'), table_name='clients')
+    op.drop_table('clients')
+    op.drop_index(op.f('ix_users_id'), table_name='users')
+    op.drop_index(op.f('ix_users_email'), table_name='users')
+    op.drop_table('users')

pyproject.toml

@@ -0,0 +1,25 @@
+[tool.ruff]
+line-length = 88
+target-version = "py39"
+
+[tool.ruff.lint]
+select = [
+    "E",  # pycodestyle errors
+    "W",  # pycodestyle warnings
+    "F",  # pyflakes
+    "I",  # isort
+    "B",  # flake8-bugbear
+    "C4", # flake8-comprehensions
+    "UP", # pyupgrade
+]
+ignore = [
+    "E501",  # line too long, handled by black
+    "B008",  # do not perform function calls in argument defaults
+    "C901",  # too complex
+]
+
+[tool.ruff.lint.per-file-ignores]
+"__init__.py" = ["F401"]
+
+[tool.ruff.lint.isort]
+known-third-party = ["fastapi", "pydantic", "sqlalchemy"]

requirements.txt

@@ -0,0 +1,10 @@
+fastapi==0.104.1
+uvicorn[standard]==0.24.0
+sqlalchemy==2.0.23
+alembic==1.12.1
+pydantic==2.5.0
+pydantic-settings==2.1.0
+python-jose[cryptography]==3.3.0
+passlib[bcrypt]==1.7.4
+python-multipart==0.0.6
+ruff==0.1.6