"""
app/utils/scope.py
------------------
Customer-scoping utility for the Janitorial QC portal.

Provides a single entry-point — get_customer_scope(user) — that returns the
set of facility IDs a customer is authorised to view, derived from their
CustomerAssignment rows.

Usage (inside any route that serves customer users):

    from app.utils.scope import get_customer_scope

    facility_ids = get_customer_scope(current_user)
    inspections  = Inspection.query.filter(
        Inspection.facility_id.in_(facility_ids)
    ).all()

For non-customer roles the function returns None, signalling that no
facility-level scoping is required (full access applies).
"""

import logging
from app.models.project import CustomerAssignment
from app.models.facility import Facility

logger = logging.getLogger(__name__)


def get_customer_scope(user) -> list[int] | None:
    """Return the list of facility IDs accessible to a customer user.

    Parameters
    ----------
    user : User
        The currently authenticated user.

    Returns
    -------
    list[int]
        Facility IDs the customer may access.  May be empty if no assignments
        exist yet — callers should treat an empty list as "no access".
    None
        Returned for non-customer roles, indicating unrestricted access.
    """
    if user.role != 'customer':
        return None  # no scoping needed for internal staff

    assignments = CustomerAssignment.query.filter_by(user_id=user.id).all()

    if not assignments:
        return []

    # Separate direct facility assignments from project-level assignments
    direct_facility_ids = {a.facility_id for a in assignments if a.facility_id}
    project_ids         = {a.project_id  for a in assignments if not a.facility_id}

    facility_ids = set(direct_facility_ids)

    # Single bulk query for all project-scoped facilities — replaces the
    # previous per-assignment Facility.query loop (N+1 pattern).
    if project_ids:
        project_facilities = (
            Facility.query
            .filter(
                Facility.project_id.in_(project_ids),
                Facility.active == True,
            )
            .all()
        )
        for f in project_facilities:
            facility_ids.add(f.id)

    logger.debug(
        'SCOPE | customer_scope | user_id=%s username=%s facility_ids=%s',
        user.id, user.username, sorted(facility_ids),
    )

    return sorted(facility_ids)