"""Profile selection utilities for FastAPI route protection.

Provides dependency functions that check the active_profile_id cookie
and return the selected User profile, or redirect to /.
"""

from typing import Optional

import structlog
from fastapi import Depends, Request
from sqlmodel import Session

from app.database import get_db_session
from app.models.user import User

logger = structlog.get_logger(__name__)


class NoProfileSelectedError(Exception):
    """Raised when a request lacks a valid profile selection."""


def get_active_profile_id(request: Request) -> Optional[int]:
    """Extract the active profile ID from the cookie.

    Args:
        request: The incoming HTTP request.

    Returns:
        The active profile user ID, or None if not set.
    """
    profile_id = request.cookies.get("active_profile_id")
    if profile_id and profile_id.isdigit():
        return int(profile_id)
    return None


def require_active_profile(request: Request, session: Session = Depends(get_db_session)) -> User:
    """FastAPI dependency that requires a valid profile selection.

    Reads the active_profile_id cookie, loads the profile from DB,
    and raises NoProfileSelectedError if missing or invalid.

    Args:
        request: The incoming HTTP request.
        session: Database session (injected by FastAPI).

    Returns:
        The selected User profile.

    Raises:
        NoProfileSelectedError: If no valid profile is selected.
    """
    profile_id = get_active_profile_id(request)
    if profile_id is None:
        raise NoProfileSelectedError()

    user = session.get(User, profile_id)
    if user is None:
        raise NoProfileSelectedError()

    return user