from typing import Generator

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.db.session import SessionLocal
from app.models.user import User


oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login")


def get_db() -> Generator[Session, None, None]:
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def get_current_user(token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)) -> User:
    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.jwt_algorithm])
        username: str | None = payload.get("sub")
        if username is None:
            raise credentials_exception
    except JWTError as exc:
        raise credentials_exception from exc
    user = db.query(User).filter(User.username == username).first()
    if not user:
        raise credentials_exception
    return user