from __future__ import annotations
from functools import lru_cache
from typing import NamedTuple, Any, Dict, Tuple
from sqlalchemy import inspect
from sqlalchemy.orm import Mapper

class RelInfo(NamedTuple):
    key: str
    uselist: bool
    target_cls: type | None

@lru_cache(maxsize=512)
def mapper_info(model: type) -> Dict[str, Any]:
    m: Mapper = inspect(model)
    cols = tuple(prop.key for prop in m.column_attrs)
    rels = { r.key: RelInfo(r.key, bool(r.uselist), getattr(r.mapper, "class_", None))
             for r in m.relationships }
    pks = tuple(c.key for c in m.primary_key)
    table = getattr(model, "__table__", None)
    return {"cols": cols, "rels": rels, "pks": pks, "table": table}

def rel_map(model: type) -> Dict[str, RelInfo]:
    return mapper_info(model)["rels"]

def column_names_for_model(model: type) -> Tuple[str, ...]:
    return mapper_info(model)["col"]