auth.py

from datetime import datetime, timedelta
from typing import Optional
from jose import JWTError, jwt
import bcrypt
import os
import secrets
from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from sqlmodel import Session, select
from uuid import UUID

from database import get_session
from models import User

# JWT settings (configurable via environment)
def get_or_create_secret_key():
    """Get secret key from env or generate and persist a new one"""
    env_key = os.getenv("SECRET_KEY")
    if env_key:
        return env_key
    
    # Check for persisted key
    key_file = ".secret_key"
    if os.path.exists(key_file):
        with open(key_file, "r") as f:
            return f.read().strip()
    
    # Generate new secure key
    new_key = secrets.token_urlsafe(32)
    with open(key_file, "w") as f:
        f.write(new_key)
    print(f"Generated new SECRET_KEY and saved to {key_file}")
    return new_key

SECRET_KEY = get_or_create_secret_key()
ALGORITHM = os.getenv("JWT_ALGORITHM", "HS256")
ACCESS_TOKEN_EXPIRE_MINUTES = int(os.getenv("ACCESS_TOKEN_EXPIRE_MINUTES", "30"))

security = HTTPBearer()

def verify_password(plain_password: str, hashed_password: str) -> bool:
    """Verify a password against a hash"""
    password_bytes = plain_password.encode('utf-8')
    hashed_bytes = hashed_password.encode('utf-8')
    return bcrypt.checkpw(password_bytes, hashed_bytes)

def get_password_hash(password: str) -> str:
    """Generate a password hash"""
    password_bytes = password.encode('utf-8')
    salt = bcrypt.gensalt()
    hashed = bcrypt.hashpw(password_bytes, salt)
    return hashed.decode('utf-8')

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=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(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    session: Session = Depends(get_session)
):
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        token = credentials.credentials
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        email = payload.get("sub")
        if email is None:
            raise credentials_exception
    except JWTError:
        raise credentials_exception
    
    statement = select(User).where(User.email == email)
    user = session.exec(statement).first()
    if user is None:
        raise credentials_exception
    return user

def require_superadmin(user: User = Depends(get_current_user)):
    if not user.is_superadmin:
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Super admin access required"
        )
    return user