from typing import Generator

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from pydantic import ValidationError
from sqlalchemy.orm import Session

from app.core.config import settings
from app.db.session import SessionLocal
from app.models.user import User
from app.schemas.token import TokenPayload

# OAuth2 token URL
oauth2_scheme = OAuth2PasswordBearer(
    tokenUrl=f"{settings.API_V1_STR}/auth/login"
)


def get_db() -> Generator:
    """
    Get a database session.
    
    Yields:
        Generator: A database session.
    """
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


def get_current_user(
    db: Session = Depends(get_db),
    token: str = Depends(oauth2_scheme)
) -> User:
    """
    Get the current authenticated user.
    
    Args:
        db: Database session
        token: JWT token
        
    Returns:
        User: The current user
        
    Raises:
        HTTPException: If authentication fails
    """
    try:
        payload = jwt.decode(
            token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
        )
        token_data = TokenPayload(**payload)
    except (JWTError, ValidationError) as err:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Could not validate credentials",
            headers={"WWW-Authenticate": "Bearer"},
        ) from err
        
    user = db.query(User).filter(User.id == token_data.sub).first()
    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_400_BAD_REQUEST,
            detail="Inactive user"
        )
    
    return user


def get_current_active_user(
    current_user: User = Depends(get_current_user),
) -> User:
    """
    Get the current active user.
    
    Args:
        current_user: Current user
        
    Returns:
        User: The current active user
        
    Raises:
        HTTPException: If the user is inactive
    """
    if not current_user.is_active:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Inactive user"
        )
    return current_user


def get_current_admin_user(
    current_user: User = Depends(get_current_user),
) -> User:
    """
    Get the current admin user.
    
    Args:
        current_user: Current user
        
    Returns:
        User: The current admin user
        
    Raises:
        HTTPException: If the user is not an admin
    """
    if current_user.role != "admin":
        raise HTTPException(
            status_code=status.HTTP_403_FORBIDDEN,
            detail="Not enough permissions"
        )
    return current_user