"""Layout signature extraction для Issue #113 (Phase 2.1 minimal).

Без `layout_type` / `balcony_count` — ждут B2B Объектив (#52).
"""

from __future__ import annotations

from typing import Literal

RoomBucket = Literal["studio", "1", "2", "3", "4+"]
AreaBin = Literal["<25", "25-40", "40-60", "60-80", "80-100", "100+"]


def room_bucket_from_flat(
    rooms: int | None,
    flat_type: str | None,
    is_studio: bool | None,
) -> RoomBucket:
    """Determine room_bucket из kn_flats полей.

    Priority:
    1. is_studio=True OR flat_type='Квартира-студия' → "studio"
    2. rooms IN (1, 2, 3) → str(rooms)
    3. rooms >= 4 → "4+"
    4. rooms = 0 (без is_studio) → "studio"
    5. fallback на "1" (rooms is None и не studio)
    """
    if is_studio is True or flat_type == "Квартира-студия":
        return "studio"
    if rooms is None:
        return "1"
    if rooms == 0:
        return "studio"
    if rooms >= 4:
        return "4+"
    if rooms in (1, 2, 3):
        return str(rooms)  # type: ignore[return-value]
    return "1"


def area_bin(area_m2: float) -> AreaBin:
    """Bucket площади per ARN-buckets (НСПД)."""
    if area_m2 < 25.0:
        return "<25"
    if area_m2 < 40.0:
        return "25-40"
    if area_m2 < 60.0:
        return "40-60"
    if area_m2 < 80.0:
        return "60-80"
    if area_m2 < 100.0:
        return "80-100"
    return "100+"


def layout_signature(room_bucket_val: RoomBucket, area_bin_val: AreaBin) -> str:
    """Deterministic string-signature для группировки."""
    return f"{room_bucket_val}__{area_bin_val}"