Authentication and Authorization with FastAPI

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

# MySQL Database URL with custom port
SQLALCHEMY_DATABASE_URL = "mysql+pymysql://root:@localhost:3306/example"

engine = create_engine(
    SQLALCHEMY_DATABASE_URL
)
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

Base = declarative_base()

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from sqlalchemy.orm import Session
from .utils import verify_password, get_password_hash, create_access_token
from .models import TokenData
from users.models import User
from .database import SessionLocal, engine, Base

Base.metadata.create_all(bind=engine)

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="auth/token")

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()

def get_user(db: Session, username: str):
    return db.query(User).filter(User.username == username).first()

def authenticate_user(db: Session, username: str, password: str):
    user = get_user(db, username)
    if not user:
        return False
    if not verify_password(password, user.hashed_password):
        return False
    return user

def get_current_user(db: Session = Depends(get_db), token: str = Depends(oauth2_scheme)):
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_data = TokenData(username=username)
    except JWTError:
        raise credentials_exception
    user = get_user(db, username=token_data.username)
    if user is None:
        raise credentials_exception
    return user

from pydantic import BaseModel

class Token(BaseModel):
    access_token: str
    token_type: str

class TokenData(BaseModel):
    username: str | None = None

from fastapi import APIRouter, Depends, HTTPException, status
from fastapi.security import OAuth2PasswordRequestForm
from sqlalchemy.orm import Session
from .dependencies import get_db, authenticate_user, create_access_token, get_user
from .models import Token
from .schemas import UserCreate, UserResponse
from users.models import User
from .utils import get_password_hash  # Import get_password_hash here

router = APIRouter()

@router.post("/token", response_model=Token)
def login_for_access_token(form_data: OAuth2PasswordRequestForm = Depends(), db: Session = Depends(get_db)):
    user = authenticate_user(db, form_data.username, form_data.password)
    if not user:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Incorrect username or password",
            headers={"WWW-Authenticate": "Bearer"},
        )
    access_token = create_access_token(data={"sub": user.username})
    return {"access_token": access_token, "token_type": "bearer"}

@router.post("/signup", response_model=UserResponse)
def signup(user: UserCreate, db: Session = Depends(get_db)):
    db_user = get_user(db, username=user.username)
    if db_user:
        raise HTTPException(status_code=400, detail="Username already registered")
    hashed_password = get_password_hash(user.password)
    db_user = User(username=user.username, hashed_password=hashed_password)
    db.add(db_user)
    db.commit()
    db.refresh(db_user)
    return db_user

from pydantic import BaseModel

class UserBase(BaseModel):
    username: str

class UserCreate(UserBase):
    password: str

class UserResponse(UserBase):
    id: int

    class Config:
        orm_mode = True

from passlib.context import CryptContext
from jose import JWTError, jwt
from datetime import datetime, timedelta

SECRET_KEY = "your_secret_key"
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

def verify_password(plain_password, hashed_password):
    return pwd_context.verify(plain_password, hashed_password)

def get_password_hash(password):
    return pwd_context.hash(password)

def create_access_token(data: dict, expires_delta: timedelta | None = None):
    to_encode = data.copy()
    if expires_delta:
        expire = datetime.utcnow() + expires_delta
    else:
        expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

from sqlalchemy import Boolean, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True, index=True)
    username = Column(String, unique=True, index=True)
    hashed_password = Column(String)
    is_active = Column(Boolean, default=True)

from fastapi import APIRouter, Depends
from sqlalchemy.orm import Session
from auth.dependencies import get_current_user, get_db
from .schemas import User
from .models import User as UserModel

router = APIRouter()

@router.get("/me", response_model=User)
def read_users_me(current_user: UserModel = Depends(get_current_user)):
    return current_user

from pydantic import BaseModel

class UserBase(BaseModel):
    username: str

class UserCreate(UserBase):
    password: str

class User(UserBase):
    id: int
    is_active: bool

    class Config:
        orm_mode = True

from fastapi import FastAPI
from auth.routes import router as auth_router
from users.routes import router as users_router

app = FastAPI()

app.include_router(auth_router, prefix="/auth", tags=["auth"])
app.include_router(users_router, prefix="/users", tags=["users"])

@app.get("/")
def read_root():
    return {"message": "Welcome to FastAPI authentication and authorization example"}