"""Shared helpers for resolving the department that owns a given task type."""
from typing import Optional


def find_owning_department(db_project, task_type: str) -> Optional[str]:
    """Return the name of the department (standard or custom) whose task_types
    list contains task_type for this project, or None if no department owns it."""
    if not task_type:
        return None

    from routers.projects import STANDARD_DEPARTMENTS

    for department in STANDARD_DEPARTMENTS:
        if task_type in department["task_types"]:
            return department["name"]

    for department in (db_project.custom_departments or []):
        if task_type in department.get("task_types", []):
            return department["name"]

    return None