"""客观题本地判分：精确比对答案集合。"""
from app.models.question import OBJECTIVE_TYPES, Question


def is_objective(q: Question) -> bool:
    return q.type in OBJECTIVE_TYPES


def can_grade_locally(q: Question) -> bool:
    """客观题且录了标准答案，才能本地判。"""
    return is_objective(q) and bool(q.correct_answer)


def grade_objective(q: Question, user_answer: list[str]) -> bool | None:
    """选择/判断题：忽略顺序与大小写，比对答案集合。

    没录标准答案时返回 None（无法判定），而不是 False —— 否则一条只是
    随手记下、还没填答案的笔记会被静默算错，并污染复习清单。
    """
    correct = {str(a).strip().upper() for a in (q.correct_answer or [])}
    if not correct:
        return None
    given = {str(a).strip().upper() for a in (user_answer or [])}
    return correct == given