"""Domain entity: PreschoolPlanningDays.

One row per (child, year): how many "förskolans planeringsdagar" (preschool
closure/planning days, e.g. "studiedagar") that child's preschool has for a
given year, and how many were actually taken.

`taken_days` is nullable on purpose: `None` means "not recorded yet", which
must be distinguishable from "recorded, and it was zero" — that distinction
is the whole point of this slice. Before this table existed,
`app/services/allocation_service.py::_preschool_reserve_days` could only
multiply `Child.preschool_planning_days_per_year` (see
`app/entities/child.py`) by the number of years in the planning horizon and
subtract the lump sum from both parents' pools, with no way to know the true
per-year number or how many parental-leave days that assumption actually
cost.

NOTE for whoever wires the allocation engine to this table (tracked as a
follow-up, not done in this change): a (child, year) pair with no row here
means "use `Child.preschool_planning_days_per_year` as the planned figure,
taken unknown" — callers must fall back to that default rather than treating
a missing row as zero days.
"""

from dataclasses import dataclass
from datetime import datetime
from uuid import UUID


@dataclass
class PreschoolPlanningDays:
    id: UUID
    child_id: UUID
    year: int
    planned_days: int
    taken_days: int | None = None
    created_at: datetime | None = None
    updated_at: datetime | None = None