"""Placement rule helpers used by ShopSpace and PREP-only edits."""
from __future__ import annotations
from typing import Iterable, Sequence, Tuple

GridPos = Tuple[int, int]

def entrance_blocked(tags) -> bool:
    return "is_entrance" in set(tags or [])

def can_rotate(footprint) -> bool:
    """All furniture may rotate; non-square footprints swap axes on rotate."""
    try:
        w, h = int(footprint[0]), int(footprint[1])
    except (TypeError, IndexError, ValueError):
        return False
    return w > 0 and h > 0

def rotate_footprint_xy(footprint, rot90: bool = False) -> Tuple[int, int]:
    """Return (w,h) after optional 90° rotate (shared with furniture_shop)."""
    w, h = int(footprint[0]), int(footprint[1])
    return (h, w) if rot90 else (w, h)

def prep_only_edit(phase: str) -> bool:
    """Layout edits allowed only in PREP."""
    return str(phase).upper() == "PREP"

def overlap(a_origin: GridPos, a_fp: Sequence[int], b_origin: GridPos, b_fp: Sequence[int]) -> bool:
    ax, ay = a_origin
    aw, ah = int(a_fp[0]), int(a_fp[1])
    bx, by = b_origin
    bw, bh = int(b_fp[0]), int(b_fp[1])
    return not (ax + aw <= bx or bx + bw <= ax or ay + ah <= by or by + bh <= ay)

def layout_comfort(free_cells: int, total_cells: int) -> bool:
    """True when enough free walking room remains."""
    if total_cells <= 0:
        return False
    return (free_cells / total_cells) >= 0.25

def validate_display_slots(slot_ids: Iterable[str], required: int = 5) -> bool:
    ids = list(slot_ids)
    return len(ids) >= required and len(set(ids)) == len(ids)