auth.py

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from passlib.context import CryptContext
from datetime import datetime, timedelta, timezone

# --- Configuration ---
SECRET_KEY = "f8e2a3b9d0c7e5f6a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4" # Use a securely generated key
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 30

# --- Password Hashing Context ---
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

# --- OAuth2 Scheme ---
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

# --- Functions ---
def verify_password(plain_password, hashed_password):
    """Verifies a plain password against a hashed one."""
    return pwd_context.verify(plain_password, hashed_password)

def get_password_hash(password):
    """Hashes a plain password."""
    return pwd_context.hash(password)

def create_access_token(data: dict):
    """Creates a new JWT access token."""
    to_encode = data.copy()
    expire = datetime.now(timezone.utc) + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    to_encode.update({"exp": expire})
    encoded_jwt = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
    return encoded_jwt

async def get_current_user(token: str = Depends(oauth2_scheme)):
    """Dependency to get the current user from a token."""
    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])
        email: str = payload.get("sub")
        if email is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    # In a real app, you would fetch the full user object from the DB here
    return {"email": email}