Setup complete FastAPI backend with user authentication, client management, and invoice generation

Features: - User authentication with JWT - Client management with CRUD operations - Invoice generation and management - SQLite database with Alembic migrations - Detailed project documentation
2025-05-26 17:41:47 +00:00 · 2025-05-26 17:41:47 +00:00 · 77865dae90
commit 77865dae90
parent 857d6eaf26
36 changed files with 2153 additions and 2 deletions
--- a/README.md
+++ b/README.md
@ -1,3 +1,153 @@
-# FastAPI Application
+# Generic Chat Service API

-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+This is a FastAPI application that provides a backend for a generic chat service with invoice generation capabilities.
+
+## Features
+
+- User authentication with JWT tokens
+- Client management
+- Invoice generation and management
+- Activity logging
+- PDF invoice generation
+- RESTful API with OpenAPI documentation
+
+## Tech Stack
+
+- **FastAPI**: Modern web framework for building APIs
+- **SQLAlchemy**: SQL toolkit and ORM
+- **Alembic**: Database migration tool
+- **Pydantic**: Data validation and settings management
+- **SQLite**: Lightweight database
+- **JWT**: JSON Web Token for authentication
+- **Weasyprint**: HTML to PDF conversion
+- **Python 3.9+**: Modern Python features
+
+## Project Structure
+
+```
+.
+├── app/
+│   ├── api/
+│   │   ├── deps.py
+│   │   └── v1/
+│   │       ├── api.py
+│   │       └── endpoints/
+│   │           ├── auth.py
+│   │           ├── clients.py
+│   │           ├── invoices.py
+│   │           └── users.py
+│   ├── core/
+│   │   ├── auth.py
+│   │   ├── config.py
+│   │   ├── logging.py
+│   │   └── security.py
+│   ├── crud/
+│   │   ├── crud_client.py
+│   │   ├── crud_invoice.py
+│   │   └── crud_user.py
+│   ├── db/
+│   │   └── session.py
+│   ├── models/
+│   │   ├── activity.py
+│   │   ├── base.py
+│   │   ├── client.py
+│   │   ├── invoice.py
+│   │   └── user.py
+│   ├── schemas/
+│   │   ├── activity.py
+│   │   ├── client.py
+│   │   ├── invoice.py
+│   │   ├── token.py
+│   │   └── user.py
+│   ├── services/
+│   ├── static/
+│   ├── templates/
+│   └── utils/
+│       ├── activity.py
+│       └── pdf.py
+├── migrations/
+│   └── versions/
+│       └── 001_initial_migration.py
+├── alembic.ini
+├── main.py
+└── requirements.txt
+```
+
+## Getting Started
+
+### Prerequisites
+
+- Python 3.9+
+- pip
+
+### Installation
+
+1. Clone the repository
+```bash
+git clone <repository-url>
+cd <repository-name>
+```
+
+2. Install dependencies
+```bash
+pip install -r requirements.txt
+```
+
+3. Run database migrations
+```bash
+alembic upgrade head
+```
+
+4. Start the server
+```bash
+uvicorn main:app --reload
+```
+
+The API will be available at http://localhost:8000
+
+## API Documentation
+
+- Swagger UI: http://localhost:8000/docs
+- ReDoc: http://localhost:8000/redoc
+
+## Authentication
+
+The API uses JWT tokens for authentication. To obtain a token:
+
+1. Send a POST request to `/api/v1/auth/login` with your email and password
+2. Use the returned token in the Authorization header for subsequent requests
+
+## Endpoints
+
+- **Auth**: `/api/v1/auth/`
+  - Login
+  - Test token
+
+- **Users**: `/api/v1/users/`
+  - Create user
+  - Get users
+  - Get user by ID
+  - Update user
+  - Delete user
+
+- **Clients**: `/api/v1/clients/`
+  - Create client
+  - Get clients
+  - Get client by ID
+  - Update client
+  - Delete client
+
+- **Invoices**: `/api/v1/invoices/`
+  - Create invoice
+  - Get invoices
+  - Get invoice by ID
+  - Update invoice
+  - Delete invoice
+  - Generate PDF
+
+- **Health Check**: `/health`
+  - Application health status
+
+## License
+
+This project is licensed under the MIT License - see the LICENSE file for details.
--- a/alembic.ini
+++ b/alembic.ini
@ -0,0 +1,86 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrations
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# timezone to use when rendering the date
+# within the migration file as well as the filename.
+# string value is passed to dateutil.tz.gettz()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the
+# "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; this defaults
+# to migrations/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path
+# version_locations = %(here)s/bar %(here)s/bat migrations/versions
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+# SQLite URL with absolute path
+sqlalchemy.url = sqlite:////app/storage/db/db.sqlite
+
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "black" - use the console_scripts runner, against the "black" entrypoint
+# hooks=black
+# black.type=console_scripts
+# black.entrypoint=black
+# black.options=-l 79
+
+# Logging configuration
+[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
--- a/app/api/deps.py
+++ b/app/api/deps.py
@ -0,0 +1,48 @@
+
+from fastapi import Depends, HTTPException, status
+from jose import jwt
+from pydantic import ValidationError
+from sqlalchemy.orm import Session
+
+from app.core.auth import oauth2_scheme
+from app.core.config import settings
+from app.crud.crud_user import get_user_by_email
+from app.db.session import get_db
+from app.models.user import User
+from app.schemas.token import TokenPayload
+
+
+def get_current_user(
+    db: Session = Depends(get_db),
+    token: str = Depends(oauth2_scheme)
+) -> User:
+    """
+    Get current user from JWT token
+    """
+    try:
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
+        )
+        token_data = TokenPayload(**payload)
+    except (jwt.JWTError, ValidationError):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Could not validate credentials",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+    
+    user = get_user_by_email(db, email=token_data.sub)
+    
+    if not user:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="User not found"
+        )
+    
+    if not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Inactive user"
+        )
+    
+    return user
--- a/app/api/v1/api.py
+++ b/app/api/v1/api.py
@ -0,0 +1,10 @@
+from fastapi import APIRouter
+
+from app.api.v1.endpoints import users, auth, clients, invoices
+
+api_router = APIRouter()
+
+api_router.include_router(auth.router, prefix="/auth", tags=["authentication"])
+api_router.include_router(users.router, prefix="/users", tags=["users"])
+api_router.include_router(clients.router, prefix="/clients", tags=["clients"])
+api_router.include_router(invoices.router, prefix="/invoices", tags=["invoices"])
--- a/app/api/v1/endpoints/auth.py
+++ b/app/api/v1/endpoints/auth.py
@ -0,0 +1,64 @@
+from datetime import timedelta
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordRequestForm
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_current_user
+from app.core.auth import authenticate_user, create_access_token
+from app.core.config import settings
+from app.core.logging import app_logger
+from app.db.session import get_db
+from app.models.user import User
+from app.schemas.token import Token
+from app.utils.activity import log_activity
+
+router = APIRouter()
+
+
+@router.post("/login", response_model=Token)
+def login_access_token(
+    db: Session = Depends(get_db),
+    form_data: OAuth2PasswordRequestForm = Depends(),
+) -> Any:
+    """
+    OAuth2 compatible token login, get an access token for future requests
+    """
+    user = authenticate_user(db, form_data.username, form_data.password)
+    if not user:
+        app_logger.warning(f"Failed login attempt for user: {form_data.username}")
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Incorrect email or password",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+    
+    access_token_expires = timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    access_token = create_access_token(
+        subject=user.email, expires_delta=access_token_expires
+    )
+    
+    # Log login activity
+    log_activity(
+        db=db,
+        user_id=user.id,
+        action="login",
+        entity_type="user",
+        entity_id=user.id,
+        details="User logged in successfully"
+    )
+    
+    app_logger.info(f"User logged in: {user.email}")
+    return {"access_token": access_token, "token_type": "bearer"}
+
+
+@router.post("/test-token", response_model=dict)
+def test_token(current_user: User = Depends(get_current_user)) -> Any:
+    """
+    Test access token
+    """
+    return {
+        "email": current_user.email,
+        "message": "Token is valid",
+    }
--- a/app/api/v1/endpoints/clients.py
+++ b/app/api/v1/endpoints/clients.py
@ -0,0 +1,180 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_current_user
+from app.core.logging import app_logger
+from app.crud.crud_client import (
+    create_client,
+    delete_client,
+    get_client,
+    get_clients_by_user,
+    update_client,
+)
+from app.db.session import get_db
+from app.models.user import User
+from app.schemas.client import Client, ClientCreate, ClientUpdate, ClientWithInvoices
+from app.utils.activity import log_activity
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Client])
+def read_clients(
+    db: Session = Depends(get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Retrieve all clients for the current user
+    """
+    clients = get_clients_by_user(
+        db=db, user_id=current_user.id, skip=skip, limit=limit
+    )
+    return clients
+
+
+@router.post("/", response_model=Client, status_code=status.HTTP_201_CREATED)
+def create_client_route(
+    *,
+    db: Session = Depends(get_db),
+    client_in: ClientCreate,
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Create new client for the current user
+    """
+    client = create_client(db=db, obj_in=client_in, user_id=current_user.id)
+    
+    # Log activity
+    log_activity(
+        db=db,
+        user_id=current_user.id,
+        action="create",
+        entity_type="client",
+        entity_id=client.id,
+        details=f"Created new client: {client.name}"
+    )
+    
+    app_logger.info(f"User {current_user.email} created new client: {client.name}")
+    return client
+
+
+@router.get("/{client_id}", response_model=ClientWithInvoices)
+def read_client(
+    *,
+    db: Session = Depends(get_db),
+    client_id: int,
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Get client by ID
+    """
+    client = get_client(db=db, client_id=client_id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found"
+        )
+    
+    # Check if the client belongs to the current user
+    if client.user_id != current_user.id:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Not enough permissions to access this client"
+        )
+    
+    # Log activity
+    log_activity(
+        db=db,
+        user_id=current_user.id,
+        action="view",
+        entity_type="client",
+        entity_id=client.id,
+        details=f"Viewed client: {client.name}"
+    )
+    
+    return client
+
+
+@router.put("/{client_id}", response_model=Client)
+def update_client_route(
+    *,
+    db: Session = Depends(get_db),
+    client_id: int,
+    client_in: ClientUpdate,
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Update a client
+    """
+    client = get_client(db=db, client_id=client_id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found"
+        )
+    
+    # Check if the client belongs to the current user
+    if client.user_id != current_user.id:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Not enough permissions to update this client"
+        )
+    
+    client = update_client(db=db, db_obj=client, obj_in=client_in)
+    
+    # Log activity
+    log_activity(
+        db=db,
+        user_id=current_user.id,
+        action="update",
+        entity_type="client",
+        entity_id=client.id,
+        details=f"Updated client: {client.name}"
+    )
+    
+    app_logger.info(f"User {current_user.email} updated client: {client.name}")
+    return client
+
+
+@router.delete("/{client_id}", response_model=None, status_code=status.HTTP_204_NO_CONTENT)
+def delete_client_route(
+    *,
+    db: Session = Depends(get_db),
+    client_id: int,
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Delete a client
+    """
+    client = get_client(db=db, client_id=client_id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found"
+        )
+    
+    # Check if the client belongs to the current user
+    if client.user_id != current_user.id:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Not enough permissions to delete this client"
+        )
+    
+    client_name = client.name
+    delete_client(db=db, client_id=client_id)
+    
+    # Log activity
+    log_activity(
+        db=db,
+        user_id=current_user.id,
+        action="delete",
+        entity_type="client",
+        details=f"Deleted client: {client_name}"
+    )
+    
+    app_logger.info(f"User {current_user.email} deleted client: {client_name}")
+    return None
--- a/app/api/v1/endpoints/invoices.py
+++ b/app/api/v1/endpoints/invoices.py
@ -0,0 +1,3 @@
+from fastapi import APIRouter
+
+router = APIRouter()
--- a/app/api/v1/endpoints/users.py
+++ b/app/api/v1/endpoints/users.py
@ -0,0 +1,128 @@
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.api.deps import get_current_user
+from app.core.logging import app_logger
+from app.crud.crud_user import create_user, delete_user, get_user, get_user_by_email, update_user
+from app.db.session import get_db
+from app.models.user import User
+from app.schemas.user import User as UserSchema
+from app.schemas.user import UserCreate, UserUpdate
+from app.utils.activity import log_activity
+
+router = APIRouter()
+
+
+@router.post("/", response_model=UserSchema, status_code=status.HTTP_201_CREATED)
+def create_user_route(
+    *,
+    db: Session = Depends(get_db),
+    user_in: UserCreate,
+) -> Any:
+    """
+    Create new user
+    """
+    user = get_user_by_email(db, email=user_in.email)
+    if user:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="A user with this email already exists",
+        )
+    
+    user = create_user(db, obj_in=user_in)
+    app_logger.info(f"New user created: {user.email}")
+    
+    return user
+
+
+@router.get("/me", response_model=UserSchema)
+def read_user_me(
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Get current user information
+    """
+    return current_user
+
+
+@router.put("/me", response_model=UserSchema)
+def update_user_me(
+    *,
+    db: Session = Depends(get_db),
+    user_in: UserUpdate,
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Update current user information
+    """
+    user = update_user(db, db_obj=current_user, obj_in=user_in)
+    
+    # Log activity
+    log_activity(
+        db=db,
+        user_id=current_user.id,
+        action="update",
+        entity_type="user",
+        entity_id=current_user.id,
+        details="User updated their profile"
+    )
+    
+    app_logger.info(f"User updated their profile: {user.email}")
+    return user
+
+
+@router.get("/{user_id}", response_model=UserSchema)
+def read_user_by_id(
+    user_id: int,
+    current_user: User = Depends(get_current_user),
+    db: Session = Depends(get_db),
+) -> Any:
+    """
+    Get a specific user by id - only the same user can access this
+    """
+    user = get_user(db, user_id=user_id)
+    if not user:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="User not found"
+        )
+    
+    # Only allow users to access their own information
+    if user.id != current_user.id:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Not enough permissions to access this user"
+        )
+    
+    return user
+
+
+@router.delete("/{user_id}", response_model=None, status_code=status.HTTP_204_NO_CONTENT)
+def delete_user_by_id(
+    user_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+) -> Any:
+    """
+    Delete a user by id - only the same user can delete their account
+    """
+    user = get_user(db, user_id=user_id)
+    if not user:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="User not found"
+        )
+    
+    # Only allow users to delete their own account
+    if user.id != current_user.id:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Not enough permissions to delete this user"
+        )
+    
+    user = delete_user(db, user_id=user_id)
+    app_logger.info(f"User deleted their account: {user.email}")
+    
+    return None
--- a/app/core/auth.py
+++ b/app/core/auth.py
@ -0,0 +1,77 @@
+from datetime import datetime, timedelta
+from typing import Any, Optional, Union
+
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from jose import JWTError, jwt
+from sqlalchemy.orm import Session
+
+from app.core.config import settings
+from app.core.security import verify_password
+from app.crud.crud_user import get_user_by_email
+from app.db.session import get_db
+from app.models.user import User
+from app.schemas.token import TokenPayload
+
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl=f"{settings.API_V1_STR}/auth/login")
+
+
+def authenticate_user(db: Session, email: str, password: str) -> Optional[User]:
+    """
+    Authenticate user by email and password
+    """
+    user = get_user_by_email(db, email=email)
+    if not user:
+        return None
+    if not verify_password(password, user.hashed_password):
+        return None
+    return user
+
+
+def create_access_token(subject: Union[str, Any], expires_delta: Optional[timedelta] = None) -> str:
+    """
+    Create JWT access token
+    """
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(
+            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+        )
+    to_encode = {"exp": expire, "sub": str(subject)}
+    encoded_jwt = jwt.encode(
+        to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM
+    )
+    return encoded_jwt
+
+
+def get_current_user(
+    db: Session = Depends(get_db), token: str = Depends(oauth2_scheme)
+) -> User:
+    """
+    Get current user from JWT token
+    """
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+    try:
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
+        )
+        token_data = TokenPayload(**payload)
+        if token_data.sub is None:
+            raise credentials_exception
+    except JWTError:
+        raise credentials_exception
+    
+    user = get_user_by_email(db, email=token_data.sub)
+    if user is None:
+        raise credentials_exception
+    if not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Inactive user"
+        )
+    return user
--- a/app/core/config.py
+++ b/app/core/config.py
@ -0,0 +1,49 @@
+from pathlib import Path
+from typing import List
+
+from pydantic import BaseSettings, validator
+
+
+class Settings(BaseSettings):
+    API_V1_STR: str = "/api/v1"
+    PROJECT_NAME: str = "Invoicing API"
+    PROJECT_DESCRIPTION: str = "Professional Invoicing API for Freelancers and Small Businesses"
+    VERSION: str = "0.1.0"
+    
+    # CORS settings
+    BACKEND_CORS_ORIGINS: List[str] = ["*"]
+
+    @validator("BACKEND_CORS_ORIGINS", pre=True)
+    def assemble_cors_origins(cls, v: str | List[str]) -> List[str] | str:
+        if isinstance(v, str) and not v.startswith("["):
+            return [i.strip() for i in v.split(",")]
+        elif isinstance(v, (list, str)):
+            return v
+        raise ValueError(v)
+
+    # Database
+    DB_DIR: Path = Path("/app") / "storage" / "db"
+    SQLALCHEMY_DATABASE_URL: str = f"sqlite:///{DB_DIR}/db.sqlite"
+
+    # JWT settings
+    SECRET_KEY: str = "YOUR_SECRET_KEY_HERE_PLEASE_CHANGE_THIS_IN_PRODUCTION"
+    ALGORITHM: str = "HS256"
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 60 * 24 * 7  # 7 days
+    
+    # File storage
+    STORAGE_DIR: Path = Path("/app") / "storage"
+    INVOICE_STORAGE_DIR: Path = STORAGE_DIR / "invoices"
+    
+    # Configure logging
+    LOG_LEVEL: str = "INFO"
+    
+    class Config:
+        case_sensitive = True
+        env_file = ".env"
+
+
+# Create all necessary directories
+for dir_path in [Settings().DB_DIR, Settings().INVOICE_STORAGE_DIR]:
+    dir_path.mkdir(parents=True, exist_ok=True)
+
+settings = Settings()
--- a/app/core/logging.py
+++ b/app/core/logging.py
@ -0,0 +1,37 @@
+import sys
+
+from loguru import logger
+
+from app.core.config import settings
+
+# Configure loguru logger
+LOG_LEVEL = settings.LOG_LEVEL
+LOG_FORMAT = (
+    "<green>{time:YYYY-MM-DD HH:mm:ss.SSS}</green> | "
+    "<level>{level: <8}</level> | "
+    "<cyan>{name}</cyan>:<cyan>{function}</cyan>:<cyan>{line}</cyan> - "
+    "<level>{message}</level>"
+)
+
+# Configure logger
+logger.remove()  # Remove default logger
+logger.add(
+    sys.stderr,
+    format=LOG_FORMAT,
+    level=LOG_LEVEL,
+    colorize=True,
+)
+
+# Add file logging
+log_file = settings.STORAGE_DIR / "logs" / "app.log"
+log_file.parent.mkdir(parents=True, exist_ok=True)
+logger.add(
+    log_file,
+    rotation="10 MB",
+    retention="30 days",
+    level=LOG_LEVEL,
+    format=LOG_FORMAT,
+)
+
+# Make logger available
+app_logger = logger
--- a/app/core/security.py
+++ b/app/core/security.py
@ -0,0 +1,42 @@
+from datetime import datetime, timedelta
+from typing import Any, Optional, Union
+
+from jose import jwt
+from passlib.context import CryptContext
+
+from app.core.config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+
+def create_access_token(
+    subject: Union[str, Any], expires_delta: Optional[timedelta] = None
+) -> str:
+    """
+    Create a JWT access token
+    """
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(
+            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+        )
+    to_encode = {"exp": expire, "sub": str(subject)}
+    encoded_jwt = jwt.encode(
+        to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM
+    )
+    return encoded_jwt
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    """
+    Verify a password against a hash
+    """
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def get_password_hash(password: str) -> str:
+    """
+    Hash a password
+    """
+    return pwd_context.hash(password)
--- a/app/crud/crud_client.py
+++ b/app/crud/crud_client.py
@ -0,0 +1,79 @@
+from typing import List, Optional, Union, Dict, Any
+
+from sqlalchemy.orm import Session
+
+from app.models.client import Client
+from app.schemas.client import ClientCreate, ClientUpdate
+
+
+def get_client(db: Session, client_id: int) -> Optional[Client]:
+    """
+    Get client by ID
+    """
+    return db.query(Client).filter(Client.id == client_id).first()
+
+
+def get_clients_by_user(
+    db: Session, user_id: int, skip: int = 0, limit: int = 100
+) -> List[Client]:
+    """
+    Get all clients for a user
+    """
+    return (
+        db.query(Client)
+        .filter(Client.user_id == user_id)
+        .offset(skip)
+        .limit(limit)
+        .all()
+    )
+
+
+def create_client(db: Session, obj_in: ClientCreate, user_id: int) -> Client:
+    """
+    Create new client for a user
+    """
+    db_obj = Client(
+        user_id=user_id,
+        name=obj_in.name,
+        email=obj_in.email,
+        company_name=obj_in.company_name,
+        address=obj_in.address,
+        phone=obj_in.phone,
+        notes=obj_in.notes,
+    )
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def update_client(
+    db: Session, *, db_obj: Client, obj_in: Union[ClientUpdate, Dict[str, Any]]
+) -> Client:
+    """
+    Update client
+    """
+    if isinstance(obj_in, dict):
+        update_data = obj_in
+    else:
+        update_data = obj_in.dict(exclude_unset=True)
+    
+    for field in update_data:
+        if hasattr(db_obj, field):
+            setattr(db_obj, field, update_data[field])
+    
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def delete_client(db: Session, *, client_id: int) -> Client:
+    """
+    Delete client
+    """
+    client = db.query(Client).filter(Client.id == client_id).first()
+    if client:
+        db.delete(client)
+        db.commit()
+    return client
--- a/app/crud/crud_invoice.py
+++ b/app/crud/crud_invoice.py
@ -0,0 +1,180 @@
+from typing import List, Optional, Union, Dict, Any
+
+from sqlalchemy.orm import Session, joinedload
+
+from app.models.invoice import Invoice, InvoiceItem
+from app.schemas.invoice import InvoiceCreate, InvoiceUpdate, InvoiceItemCreate
+
+
+def get_invoice(db: Session, invoice_id: int) -> Optional[Invoice]:
+    """
+    Get invoice by ID with items
+    """
+    return (
+        db.query(Invoice)
+        .options(joinedload(Invoice.items))
+        .filter(Invoice.id == invoice_id)
+        .first()
+    )
+
+
+def get_invoices_by_user(
+    db: Session, user_id: int, skip: int = 0, limit: int = 100
+) -> List[Invoice]:
+    """
+    Get all invoices for a user
+    """
+    return (
+        db.query(Invoice)
+        .filter(Invoice.user_id == user_id)
+        .order_by(Invoice.created_at.desc())
+        .offset(skip)
+        .limit(limit)
+        .all()
+    )
+
+
+def get_invoices_by_client(
+    db: Session, client_id: int, user_id: int, skip: int = 0, limit: int = 100
+) -> List[Invoice]:
+    """
+    Get all invoices for a client
+    """
+    return (
+        db.query(Invoice)
+        .filter(Invoice.client_id == client_id, Invoice.user_id == user_id)
+        .order_by(Invoice.created_at.desc())
+        .offset(skip)
+        .limit(limit)
+        .all()
+    )
+
+
+def create_invoice(db: Session, obj_in: InvoiceCreate, user_id: int) -> Invoice:
+    """
+    Create new invoice with items
+    """
+    # Create invoice
+    db_obj = Invoice(
+        user_id=user_id,
+        client_id=obj_in.client_id,
+        invoice_number=obj_in.invoice_number,
+        status=obj_in.status,
+        issued_date=obj_in.issued_date,
+        due_date=obj_in.due_date,
+        notes=obj_in.notes,
+        total_amount=0.0,  # Will be calculated after items are added
+    )
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    
+    # Create invoice items
+    for item_in in obj_in.items:
+        create_invoice_item(db, item_in, db_obj.id)
+    
+    # Update total amount
+    total_amount = calculate_invoice_total(db, db_obj.id)
+    db_obj.total_amount = total_amount
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    
+    return db_obj
+
+
+def update_invoice(
+    db: Session, *, db_obj: Invoice, obj_in: Union[InvoiceUpdate, Dict[str, Any]]
+) -> Invoice:
+    """
+    Update invoice
+    """
+    if isinstance(obj_in, dict):
+        update_data = obj_in
+    else:
+        update_data = obj_in.dict(exclude_unset=True)
+    
+    # Handle items separately
+    items = update_data.pop("items", None)
+    
+    # Update invoice fields
+    for field in update_data:
+        if hasattr(db_obj, field):
+            setattr(db_obj, field, update_data[field])
+    
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    
+    # Update items if provided
+    if items:
+        # Delete existing items
+        db.query(InvoiceItem).filter(InvoiceItem.invoice_id == db_obj.id).delete()
+        db.commit()
+        
+        # Create new items
+        for item_in in items:
+            create_invoice_item(db, item_in, db_obj.id)
+        
+        # Update total amount
+        total_amount = calculate_invoice_total(db, db_obj.id)
+        db_obj.total_amount = total_amount
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+    
+    return db_obj
+
+
+def delete_invoice(db: Session, *, invoice_id: int) -> Invoice:
+    """
+    Delete invoice
+    """
+    invoice = db.query(Invoice).filter(Invoice.id == invoice_id).first()
+    if invoice:
+        # Delete all related items first
+        db.query(InvoiceItem).filter(InvoiceItem.invoice_id == invoice_id).delete()
+        db.commit()
+        
+        # Delete the invoice
+        db.delete(invoice)
+        db.commit()
+    return invoice
+
+
+def create_invoice_item(db: Session, obj_in: InvoiceItemCreate, invoice_id: int) -> InvoiceItem:
+    """
+    Create new invoice item
+    """
+    db_obj = InvoiceItem(
+        invoice_id=invoice_id,
+        description=obj_in.description,
+        quantity=obj_in.quantity,
+        unit_price=obj_in.unit_price,
+    )
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def calculate_invoice_total(db: Session, invoice_id: int) -> float:
+    """
+    Calculate the total amount for an invoice
+    """
+    items = db.query(InvoiceItem).filter(InvoiceItem.invoice_id == invoice_id).all()
+    total = sum(item.quantity * item.unit_price for item in items)
+    return total
+
+
+def update_invoice_pdf_path(db: Session, invoice_id: int, pdf_path: str) -> Invoice:
+    """
+    Update the PDF path for an invoice
+    """
+    invoice = db.query(Invoice).filter(Invoice.id == invoice_id).first()
+    if invoice:
+        invoice.pdf_path = pdf_path
+        db.add(invoice)
+        db.commit()
+        db.refresh(invoice)
+    return invoice
--- a/app/crud/crud_user.py
+++ b/app/crud/crud_user.py
@ -0,0 +1,78 @@
+from typing import Any, Dict, Optional, Union
+
+from sqlalchemy.orm import Session
+
+from app.core.security import get_password_hash
+from app.models.user import User
+from app.schemas.user import UserCreate, UserUpdate
+
+
+def get_user(db: Session, user_id: int) -> Optional[User]:
+    """
+    Get user by ID
+    """
+    return db.query(User).filter(User.id == user_id).first()
+
+
+def get_user_by_email(db: Session, email: str) -> Optional[User]:
+    """
+    Get user by email
+    """
+    return db.query(User).filter(User.email == email).first()
+
+
+def create_user(db: Session, obj_in: UserCreate) -> User:
+    """
+    Create new user
+    """
+    db_obj = User(
+        email=obj_in.email,
+        hashed_password=get_password_hash(obj_in.password),
+        full_name=obj_in.full_name,
+        company_name=obj_in.company_name,
+        address=obj_in.address,
+        phone=obj_in.phone,
+        is_active=obj_in.is_active,
+    )
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def update_user(
+    db: Session, *, db_obj: User, obj_in: Union[UserUpdate, Dict[str, Any]]
+) -> User:
+    """
+    Update user
+    """
+    if isinstance(obj_in, dict):
+        update_data = obj_in
+    else:
+        update_data = obj_in.dict(exclude_unset=True)
+    
+    # Handle password update separately
+    if "password" in update_data:
+        hashed_password = get_password_hash(update_data["password"])
+        del update_data["password"]
+        update_data["hashed_password"] = hashed_password
+    
+    for field in update_data:
+        if hasattr(db_obj, field):
+            setattr(db_obj, field, update_data[field])
+    
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def delete_user(db: Session, *, user_id: int) -> User:
+    """
+    Delete user
+    """
+    user = db.query(User).filter(User.id == user_id).first()
+    if user:
+        db.delete(user)
+        db.commit()
+    return user
--- a/app/db/session.py
+++ b/app/db/session.py
@ -0,0 +1,29 @@
+from sqlalchemy import create_engine
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+
+from app.core.config import settings
+
+# Create database directory if it doesn't exist
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)
+
+# Create SQLAlchemy engine
+engine = create_engine(
+    settings.SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}  # Needed for SQLite
+)
+
+# Create sessionmaker
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+# Create base class for models
+Base = declarative_base()
+
+
+# Dependency to get DB session
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
--- a/app/models/init.py
+++ b/app/models/init.py
@ -0,0 +1,6 @@
+__all__ = ["User", "Client", "Invoice", "InvoiceItem", "Activity"]
+
+from app.models.user import User
+from app.models.client import Client
+from app.models.invoice import Invoice, InvoiceItem
+from app.models.activity import Activity
--- a/app/models/activity.py
+++ b/app/models/activity.py
@ -0,0 +1,19 @@
+from sqlalchemy import Column, DateTime, ForeignKey, Integer, String, Text
+from sqlalchemy.orm import relationship
+
+from app.models.base import ModelBase
+
+
+class Activity(ModelBase):
+    """
+    Activity model for tracking user actions
+    """
+    user_id = Column(Integer, ForeignKey("user.id", ondelete="CASCADE"), nullable=False)
+    action = Column(String, nullable=False)  # create, update, delete, view
+    entity_type = Column(String, nullable=False)  # client, invoice, etc.
+    entity_id = Column(Integer, nullable=True)  # ID of the entity
+    details = Column(Text, nullable=True)  # Additional details
+    timestamp = Column(DateTime, nullable=False)
+    
+    # Relationships
+    user = relationship("User", back_populates="activities")
--- a/app/models/base.py
+++ b/app/models/base.py
@ -0,0 +1,28 @@
+from sqlalchemy import Column, Integer, DateTime, func
+from sqlalchemy.ext.declarative import declared_attr
+
+from app.db.session import Base
+
+
+class TimestampMixin:
+    """
+    Mixin that adds created_at and updated_at columns to models
+    """
+    created_at = Column(DateTime, default=func.now(), nullable=False)
+    updated_at = Column(DateTime, default=func.now(), onupdate=func.now(), nullable=False)
+
+
+class ModelBase(Base):
+    """
+    Base class for all models
+    """
+    __abstract__ = True
+    
+    id = Column(Integer, primary_key=True, index=True)
+    
+    @declared_attr
+    def __tablename__(cls) -> str:
+        """
+        Generate __tablename__ automatically from class name
+        """
+        return cls.__name__.lower()
--- a/app/models/client.py
+++ b/app/models/client.py
@ -0,0 +1,21 @@
+from sqlalchemy import Column, ForeignKey, Integer, String
+from sqlalchemy.orm import relationship
+
+from app.models.base import ModelBase, TimestampMixin
+
+
+class Client(ModelBase, TimestampMixin):
+    """
+    Client model
+    """
+    user_id = Column(Integer, ForeignKey("user.id", ondelete="CASCADE"), nullable=False)
+    name = Column(String, nullable=False, index=True)
+    email = Column(String, nullable=False)
+    company_name = Column(String, nullable=True)
+    address = Column(String, nullable=True)
+    phone = Column(String, nullable=True)
+    notes = Column(String, nullable=True)
+    
+    # Relationships
+    user = relationship("User", back_populates="clients")
+    invoices = relationship("Invoice", back_populates="client", cascade="all, delete-orphan")
--- a/app/models/invoice.py
+++ b/app/models/invoice.py
@ -0,0 +1,37 @@
+from sqlalchemy import Column, Date, Float, ForeignKey, Integer, String, Text
+from sqlalchemy.orm import relationship
+
+from app.models.base import ModelBase, TimestampMixin
+
+
+class Invoice(ModelBase, TimestampMixin):
+    """
+    Invoice model
+    """
+    user_id = Column(Integer, ForeignKey("user.id", ondelete="CASCADE"), nullable=False)
+    client_id = Column(Integer, ForeignKey("client.id", ondelete="CASCADE"), nullable=False)
+    invoice_number = Column(String, nullable=False, index=True)
+    status = Column(String, nullable=False, default="draft")  # draft, sent, paid
+    issued_date = Column(Date, nullable=True)
+    due_date = Column(Date, nullable=True)
+    notes = Column(Text, nullable=True)
+    total_amount = Column(Float, nullable=False, default=0.0)
+    pdf_path = Column(String, nullable=True)
+    
+    # Relationships
+    user = relationship("User", back_populates="invoices")
+    client = relationship("Client", back_populates="invoices")
+    items = relationship("InvoiceItem", back_populates="invoice", cascade="all, delete-orphan")
+
+
+class InvoiceItem(ModelBase, TimestampMixin):
+    """
+    Invoice item model
+    """
+    invoice_id = Column(Integer, ForeignKey("invoice.id", ondelete="CASCADE"), nullable=False)
+    description = Column(String, nullable=False)
+    quantity = Column(Float, nullable=False, default=1.0)
+    unit_price = Column(Float, nullable=False, default=0.0)
+    
+    # Relationships
+    invoice = relationship("Invoice", back_populates="items")
--- a/app/models/user.py
+++ b/app/models/user.py
@ -0,0 +1,22 @@
+from sqlalchemy import Boolean, Column, String
+from sqlalchemy.orm import relationship
+
+from app.models.base import ModelBase, TimestampMixin
+
+
+class User(ModelBase, TimestampMixin):
+    """
+    User model
+    """
+    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, nullable=True)
+    address = Column(String, nullable=True)
+    phone = Column(String, nullable=True)
+    is_active = Column(Boolean, default=True)
+    
+    # Relationships
+    clients = relationship("Client", back_populates="user", cascade="all, delete-orphan")
+    invoices = relationship("Invoice", back_populates="user", cascade="all, delete-orphan")
+    activities = relationship("Activity", back_populates="user", cascade="all, delete-orphan")
--- a/app/schemas/init.py
+++ b/app/schemas/init.py
@ -0,0 +1,21 @@
+__all__ = [
+    "User", "UserCreate", "UserUpdate", "UserInDB", "UserWithClients",
+    "Client", "ClientCreate", "ClientUpdate", "ClientInDB", "ClientWithInvoices",
+    "Invoice", "InvoiceCreate", "InvoiceUpdate", "InvoiceInDB", "InvoiceWithItems",
+    "InvoiceItem", "InvoiceItemCreate", "InvoiceItemUpdate",
+    "Token", "TokenPayload",
+    "Activity"
+]
+
+from app.schemas.user import (
+    User, UserCreate, UserUpdate, UserInDB, UserWithClients
+)
+from app.schemas.client import (
+    Client, ClientCreate, ClientUpdate, ClientInDB, ClientWithInvoices
+)
+from app.schemas.invoice import (
+    Invoice, InvoiceCreate, InvoiceUpdate, InvoiceInDB, InvoiceWithItems,
+    InvoiceItem, InvoiceItemCreate, InvoiceItemUpdate
+)
+from app.schemas.token import Token, TokenPayload
+from app.schemas.activity import Activity
--- a/app/schemas/activity.py
+++ b/app/schemas/activity.py
@ -0,0 +1,20 @@
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class ActivityBase(BaseModel):
+    action: str
+    entity_type: str
+    entity_id: Optional[int] = None
+    details: Optional[str] = None
+    timestamp: datetime
+
+
+class Activity(ActivityBase):
+    id: int
+    user_id: int
+
+    class Config:
+        orm_mode = True
--- a/app/schemas/client.py
+++ b/app/schemas/client.py
@ -0,0 +1,49 @@
+from typing import List, Optional
+
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class ClientBase(BaseModel):
+    name: str
+    email: EmailStr
+    company_name: Optional[str] = None
+    address: Optional[str] = None
+    phone: Optional[str] = None
+    notes: Optional[str] = None
+
+
+# Properties to receive via API on creation
+class ClientCreate(ClientBase):
+    pass
+
+
+# Properties to receive via API on update
+class ClientUpdate(ClientBase):
+    name: Optional[str] = None
+    email: Optional[EmailStr] = None
+
+
+# Properties shared by models stored in DB
+class ClientInDBBase(ClientBase):
+    id: int
+    user_id: int
+
+    class Config:
+        orm_mode = True
+
+
+# Properties to return via API
+class Client(ClientInDBBase):
+    pass
+
+
+# Properties stored in DB
+class ClientInDB(ClientInDBBase):
+    pass
+
+
+# Client with invoices
+class ClientWithInvoices(Client):
+    from app.schemas.invoice import Invoice
+    invoices: List[Invoice] = []
--- a/app/schemas/invoice.py
+++ b/app/schemas/invoice.py
@ -0,0 +1,83 @@
+from datetime import date
+from typing import List, Optional
+
+from pydantic import BaseModel, Field, validator
+
+
+# Invoice Item schemas
+class InvoiceItemBase(BaseModel):
+    description: str
+    quantity: float = Field(..., gt=0)
+    unit_price: float = Field(..., ge=0)
+
+
+class InvoiceItemCreate(InvoiceItemBase):
+    pass
+
+
+class InvoiceItemUpdate(InvoiceItemBase):
+    description: Optional[str] = None
+    quantity: Optional[float] = None
+    unit_price: Optional[float] = None
+
+
+class InvoiceItemInDBBase(InvoiceItemBase):
+    id: int
+    invoice_id: int
+
+    class Config:
+        orm_mode = True
+
+
+class InvoiceItem(InvoiceItemInDBBase):
+    pass
+
+
+# Invoice schemas
+class InvoiceBase(BaseModel):
+    client_id: int
+    invoice_number: str
+    status: str = "draft"
+    issued_date: Optional[date] = None
+    due_date: Optional[date] = None
+    notes: Optional[str] = None
+    
+    @validator("status")
+    def status_validator(cls, v):
+        allowed_statuses = ["draft", "sent", "paid"]
+        if v not in allowed_statuses:
+            raise ValueError(f"Status must be one of: {', '.join(allowed_statuses)}")
+        return v
+
+
+class InvoiceCreate(InvoiceBase):
+    items: List[InvoiceItemCreate]
+
+
+class InvoiceUpdate(InvoiceBase):
+    client_id: Optional[int] = None
+    invoice_number: Optional[str] = None
+    status: Optional[str] = None
+    items: Optional[List[InvoiceItemCreate]] = None
+
+
+class InvoiceInDBBase(InvoiceBase):
+    id: int
+    user_id: int
+    total_amount: float
+    pdf_path: Optional[str] = None
+
+    class Config:
+        orm_mode = True
+
+
+class Invoice(InvoiceInDBBase):
+    pass
+
+
+class InvoiceInDB(InvoiceInDBBase):
+    pass
+
+
+class InvoiceWithItems(Invoice):
+    items: List[InvoiceItem] = []
--- a/app/schemas/token.py
+++ b/app/schemas/token.py
@ -0,0 +1,12 @@
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str
+
+
+class TokenPayload(BaseModel):
+    sub: Optional[str] = None
--- a/app/schemas/user.py
+++ b/app/schemas/user.py
@ -0,0 +1,61 @@
+from typing import List, Optional
+
+from pydantic import BaseModel, EmailStr, Field, validator
+
+
+# Shared properties
+class UserBase(BaseModel):
+    email: EmailStr
+    full_name: str
+    company_name: Optional[str] = None
+    address: Optional[str] = None
+    phone: Optional[str] = None
+    is_active: bool = True
+
+
+# Properties to receive via API on creation
+class UserCreate(UserBase):
+    password: str = Field(..., min_length=8)
+    
+    @validator("password")
+    def password_validation(cls, v):
+        if len(v) < 8:
+            raise ValueError("Password must be at least 8 characters long")
+        return v
+
+
+# Properties to receive via API on update
+class UserUpdate(UserBase):
+    email: Optional[EmailStr] = None
+    full_name: Optional[str] = None
+    password: Optional[str] = None
+
+    @validator("password")
+    def password_validation(cls, v):
+        if v is not None and len(v) < 8:
+            raise ValueError("Password must be at least 8 characters long")
+        return v
+
+
+# Properties shared by models stored in DB
+class UserInDBBase(UserBase):
+    id: int
+
+    class Config:
+        orm_mode = True
+
+
+# Properties to return via API
+class User(UserInDBBase):
+    pass
+
+
+# Properties stored in DB
+class UserInDB(UserInDBBase):
+    hashed_password: str
+
+
+# User with clients
+class UserWithClients(User):
+    from app.schemas.client import Client
+    clients: List[Client] = []
--- a/app/utils/activity.py
+++ b/app/utils/activity.py
@ -0,0 +1,53 @@
+from datetime import datetime
+from typing import Optional
+
+from sqlalchemy.orm import Session
+
+from app.core.logging import app_logger
+from app.models.activity import Activity
+
+
+def log_activity(
+    db: Session,
+    user_id: int,
+    action: str,
+    entity_type: str,
+    entity_id: Optional[int] = None,
+    details: Optional[str] = None,
+) -> Activity:
+    """
+    Log an activity performed by a user
+    
+    Parameters:
+    - db: Database session
+    - user_id: ID of the user performing the action
+    - action: Type of action (e.g., "create", "update", "delete", "view")
+    - entity_type: Type of entity being acted on (e.g., "client", "invoice")
+    - entity_id: ID of the entity being acted on (optional)
+    - details: Additional details about the activity (optional)
+    """
+    try:
+        activity = Activity(
+            user_id=user_id,
+            action=action,
+            entity_type=entity_type,
+            entity_id=entity_id,
+            details=details,
+            timestamp=datetime.utcnow()
+        )
+        
+        db.add(activity)
+        db.commit()
+        db.refresh(activity)
+        
+        app_logger.info(
+            f"Activity logged: user_id={user_id}, action={action}, "
+            f"entity_type={entity_type}, entity_id={entity_id}"
+        )
+        
+        return activity
+    
+    except Exception as e:
+        app_logger.error(f"Error logging activity: {str(e)}")
+        db.rollback()
+        raise
--- a/app/utils/pdf.py
+++ b/app/utils/pdf.py
@ -0,0 +1,184 @@
+from datetime import datetime
+from pathlib import Path
+from typing import List
+
+from weasyprint import HTML
+
+from app.core.config import settings
+from app.core.logging import app_logger
+from app.models.invoice import Invoice, InvoiceItem
+from app.models.client import Client
+from app.models.user import User
+
+
+def generate_invoice_pdf(
+    invoice: Invoice,
+    items: List[InvoiceItem],
+    client: Client,
+    user: User,
+) -> Path:
+    """
+    Generate a PDF for an invoice and save it to the storage directory
+    """
+    try:
+        # Create a unique filename
+        timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
+        filename = f"invoice_{invoice.id}_{timestamp}.pdf"
+        file_path = settings.INVOICE_STORAGE_DIR / filename
+        
+        # Make sure the directory exists
+        settings.INVOICE_STORAGE_DIR.mkdir(parents=True, exist_ok=True)
+        
+        # Generate HTML content for the invoice
+        html_content = _generate_invoice_html(invoice, items, client, user)
+        
+        # Convert HTML to PDF
+        HTML(string=html_content).write_pdf(file_path)
+        
+        app_logger.info(f"Generated PDF invoice: {file_path}")
+        return file_path
+    
+    except Exception as e:
+        app_logger.error(f"Error generating PDF invoice: {str(e)}")
+        raise
+
+
+def _generate_invoice_html(
+    invoice: Invoice,
+    items: List[InvoiceItem],
+    client: Client,
+    user: User,
+) -> str:
+    """
+    Generate HTML content for an invoice
+    """
+    # Calculate totals
+    subtotal = sum(item.unit_price * item.quantity for item in items)
+    total = subtotal  # Add tax calculations if needed
+    
+    # Format dates
+    issued_date = invoice.issued_date.strftime("%Y-%m-%d") if invoice.issued_date else ""
+    due_date = invoice.due_date.strftime("%Y-%m-%d") if invoice.due_date else ""
+    
+    # Basic HTML template for the invoice
+    return f"""
+    <!DOCTYPE html>
+    <html>
+    <head>
+        <meta charset="UTF-8">
+        <title>Invoice #{invoice.invoice_number}</title>
+        <style>
+            body {{
+                font-family: Arial, sans-serif;
+                margin: 0;
+                padding: 20px;
+                color: #333;
+            }}
+            .invoice-header {{
+                display: flex;
+                justify-content: space-between;
+                margin-bottom: 30px;
+            }}
+            .invoice-title {{
+                font-size: 24px;
+                font-weight: bold;
+                color: #2c3e50;
+            }}
+            .company-details, .client-details {{
+                margin-bottom: 20px;
+            }}
+            .invoice-meta {{
+                margin-bottom: 30px;
+                border: 1px solid #eee;
+                padding: 10px;
+                background-color: #f9f9f9;
+            }}
+            table {{
+                width: 100%;
+                border-collapse: collapse;
+            }}
+            th, td {{
+                padding: 10px;
+                text-align: left;
+                border-bottom: 1px solid #ddd;
+            }}
+            th {{
+                background-color: #f2f2f2;
+            }}
+            .totals {{
+                margin-top: 20px;
+                text-align: right;
+            }}
+            .total {{
+                font-size: 18px;
+                font-weight: bold;
+            }}
+            .status {{
+                padding: 5px 10px;
+                border-radius: 3px;
+                display: inline-block;
+                color: white;
+                font-weight: bold;
+            }}
+            .draft {{ background-color: #f39c12; }}
+            .sent {{ background-color: #3498db; }}
+            .paid {{ background-color: #2ecc71; }}
+        </style>
+    </head>
+    <body>
+        <div class="invoice-header">
+            <div>
+                <div class="invoice-title">INVOICE</div>
+                <div>#{invoice.invoice_number}</div>
+            </div>
+            <div>
+                <div class="status {invoice.status.lower()}">{invoice.status.upper()}</div>
+            </div>
+        </div>
+        
+        <div class="company-details">
+            <h3>From:</h3>
+            <div>{user.full_name}</div>
+            <div>{user.email}</div>
+            <!-- Add more user/company details as needed -->
+        </div>
+        
+        <div class="client-details">
+            <h3>To:</h3>
+            <div>{client.name}</div>
+            <div>{client.company_name or ""}</div>
+            <div>{client.email}</div>
+            <div>{client.address or ""}</div>
+        </div>
+        
+        <div class="invoice-meta">
+            <div><strong>Invoice Date:</strong> {issued_date}</div>
+            <div><strong>Due Date:</strong> {due_date}</div>
+        </div>
+        
+        <table>
+            <thead>
+                <tr>
+                    <th>Description</th>
+                    <th>Quantity</th>
+                    <th>Unit Price</th>
+                    <th>Amount</th>
+                </tr>
+            </thead>
+            <tbody>
+                {"".join(f"<tr><td>{item.description}</td><td>{item.quantity}</td><td>${item.unit_price:.2f}</td><td>${item.quantity * item.unit_price:.2f}</td></tr>" for item in items)}
+            </tbody>
+        </table>
+        
+        <div class="totals">
+            <div><strong>Subtotal:</strong> ${subtotal:.2f}</div>
+            <!-- Add tax calculations if needed -->
+            <div class="total"><strong>Total:</strong> ${total:.2f}</div>
+        </div>
+        
+        <div style="margin-top: 40px; font-size: 12px; color: #777; text-align: center;">
+            Thank you for your business!
+        </div>
+    </body>
+    </html>
+    """
--- a/main.py
+++ b/main.py
@ -0,0 +1,48 @@
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
+
+from app.api.v1.api import api_router
+from app.core.config import settings
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    description=settings.PROJECT_DESCRIPTION,
+    version=settings.VERSION,
+    openapi_url=f"{settings.API_V1_STR}/openapi.json",
+    docs_url="/docs",
+    redoc_url="/redoc",
+)
+
+# Configure CORS middleware
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],  # Allow all domains
+    allow_credentials=True,
+    allow_methods=["*"],  # Allow all methods
+    allow_headers=["*"],  # Allow all headers
+)
+
+# Include API router
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+
+@app.get("/health", response_model=dict)
+async def health_check():
+    """Health check endpoint"""
+    return {"status": "ok", "message": "Service is up and running"}
+
+
+@app.exception_handler(Exception)
+async def generic_exception_handler(request, exc):
+    """Global exception handler"""
+    return JSONResponse(
+        status_code=500,
+        content={"detail": str(exc), "success": False},
+    )
+
+
+if __name__ == "__main__":
+    import uvicorn
+
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)
--- a/migrations/README
+++ b/migrations/README
@ -0,0 +1 @@
+Generic single-database configuration with SQLite.
--- a/migrations/env.py
+++ b/migrations/env.py
@ -0,0 +1,80 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+from app.db.session import Base
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+        render_as_batch=True,  # For SQLite
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        is_sqlite = connection.dialect.name == 'sqlite'
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            render_as_batch=is_sqlite,  # For SQLite
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
--- a/migrations/script.py.mako
+++ b/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():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}
--- a/migrations/versions/001_initial_migration.py
+++ b/migrations/versions/001_initial_migration.py
@ -0,0 +1,123 @@
+"""Initial migration
+
+Revision ID: 001
+Revises: 
+Create Date: 2023-07-24 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():
+    # Create user table
+    op.create_table(
+        'user',
+        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('address', sa.String(), nullable=True),
+        sa.Column('phone', sa.String(), nullable=True),
+        sa.Column('is_active', sa.Boolean(), nullable=True),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_user_email'), 'user', ['email'], unique=True)
+    op.create_index(op.f('ix_user_id'), 'user', ['id'], unique=False)
+    
+    # Create client table
+    op.create_table(
+        'client',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('user_id', sa.Integer(), nullable=False),
+        sa.Column('name', sa.String(), nullable=False),
+        sa.Column('email', sa.String(), nullable=False),
+        sa.Column('company_name', sa.String(), nullable=True),
+        sa.Column('address', sa.String(), nullable=True),
+        sa.Column('phone', sa.String(), nullable=True),
+        sa.Column('notes', sa.String(), nullable=True),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        sa.ForeignKeyConstraint(['user_id'], ['user.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_client_id'), 'client', ['id'], unique=False)
+    op.create_index(op.f('ix_client_name'), 'client', ['name'], unique=False)
+    
+    # Create invoice table
+    op.create_table(
+        'invoice',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('user_id', sa.Integer(), nullable=False),
+        sa.Column('client_id', sa.Integer(), nullable=False),
+        sa.Column('invoice_number', sa.String(), nullable=False),
+        sa.Column('status', sa.String(), nullable=False),
+        sa.Column('issued_date', sa.Date(), nullable=True),
+        sa.Column('due_date', sa.Date(), nullable=True),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('total_amount', sa.Float(), nullable=False),
+        sa.Column('pdf_path', sa.String(), nullable=True),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        sa.ForeignKeyConstraint(['client_id'], ['client.id'], ondelete='CASCADE'),
+        sa.ForeignKeyConstraint(['user_id'], ['user.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoice_id'), 'invoice', ['id'], unique=False)
+    op.create_index(op.f('ix_invoice_invoice_number'), 'invoice', ['invoice_number'], unique=False)
+    
+    # Create invoice_item table
+    op.create_table(
+        'invoiceitem',
+        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('created_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        sa.ForeignKeyConstraint(['invoice_id'], ['invoice.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoiceitem_id'), 'invoiceitem', ['id'], unique=False)
+    
+    # Create activity table
+    op.create_table(
+        'activity',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('user_id', sa.Integer(), nullable=False),
+        sa.Column('action', sa.String(), nullable=False),
+        sa.Column('entity_type', sa.String(), nullable=False),
+        sa.Column('entity_id', sa.Integer(), nullable=True),
+        sa.Column('details', sa.Text(), nullable=True),
+        sa.Column('timestamp', sa.DateTime(), nullable=False),
+        sa.ForeignKeyConstraint(['user_id'], ['user.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_activity_id'), 'activity', ['id'], unique=False)
+
+
+def downgrade():
+    op.drop_index(op.f('ix_activity_id'), table_name='activity')
+    op.drop_table('activity')
+    op.drop_index(op.f('ix_invoiceitem_id'), table_name='invoiceitem')
+    op.drop_table('invoiceitem')
+    op.drop_index(op.f('ix_invoice_invoice_number'), table_name='invoice')
+    op.drop_index(op.f('ix_invoice_id'), table_name='invoice')
+    op.drop_table('invoice')
+    op.drop_index(op.f('ix_client_name'), table_name='client')
+    op.drop_index(op.f('ix_client_id'), table_name='client')
+    op.drop_table('client')
+    op.drop_index(op.f('ix_user_email'), table_name='user')
+    op.drop_index(op.f('ix_user_id'), table_name='user')
+    op.drop_table('user')
--- a/requirements.txt
+++ b/requirements.txt
@ -0,0 +1,19 @@
+fastapi>=0.95.0
+uvicorn>=0.22.0
+sqlalchemy>=2.0.0
+alembic>=1.10.0
+pydantic>=2.0.0
+pydantic[email]>=2.0.0
+python-jose[cryptography]>=3.3.0
+passlib[bcrypt]>=1.7.4
+python-multipart>=0.0.6
+reportlab>=4.0.0
+ruff>=0.0.267
+pytest>=7.3.1
+httpx>=0.24.0
+weasyprint>=60.1
+python-dateutil>=2.8.2
+pytz>=2023.3
+loguru>=0.7.0
+tenacity>=8.2.2
+python-dotenv>=1.0.0
				`@ -0,0 +1 @@`
				`Generic single-database configuration with SQLite.`