# dao/stu_score_dao.py
# 学生成绩数据访问层：含成绩等级自动判定的业务规则

from decimal import Decimal
from typing import List, Optional, Tuple

from sqlalchemy.orm import Session

from dao.exceptions import ConflictError, NotFoundError
from dao.pagination import paginate
from dao.stu_dao import assert_stu_alive
from model.stu_score_model import StuScore


def compute_score_level(score: Decimal) -> str:
    """根据分数自动判定等级：>=90 优秀、80-89 良好、60-79 普通、<60 不及格"""
    if score >= 90:
        return "优秀"
    if score >= 80:
        return "良好"
    if score >= 60:
        return "普通"
    return "不及格"


def assert_score_alive(db: Session, score_id: int, detail: Optional[str] = None) -> StuScore:
    """确认成绩记录存在且未删除，否则抛 NotFoundError。"""
    score = (
        db.query(StuScore)
        .filter(StuScore.id == score_id, StuScore.is_deleted == False)  # noqa: E712 布尔列
        .first()
    )
    if not score:
        raise NotFoundError(detail or "成绩记录不存在或已删除")
    return score


def list_scores(
    db: Session,
    page: int,
    size: int,
    stu_id: Optional[str] = None,
    score_level: Optional[str] = None,
) -> Tuple[int, List[StuScore]]:
    """分页查询未删除的成绩，支持按学生 / 等级过滤。"""
    query = db.query(StuScore).filter(StuScore.is_deleted == False)  # noqa: E712 布尔列
    if stu_id:
        query = query.filter(StuScore.stu_id == stu_id)
    if score_level:
        query = query.filter(StuScore.score_level == score_level)
    return paginate(query, page, size, order_by=StuScore.id)


def list_scores_by_student(db: Session, stu_id: str) -> List[StuScore]:
    """查询某学生的全部有效成绩，按考试轮次升序。"""
    return (
        db.query(StuScore)
        .filter(StuScore.stu_id == stu_id, StuScore.is_deleted == False)  # noqa: E712
        .order_by(StuScore.exam_attempt)
        .all()
    )


def create_score(db: Session, data: dict) -> StuScore:
    """新增成绩：校验学生存在、同轮次不重复，并在未指定等级时自动判定。"""
    assert_stu_alive(db, data["stu_id"])

    exists = (
        db.query(StuScore)
        .filter(
            StuScore.stu_id == data["stu_id"],
            StuScore.exam_attempt == data["exam_attempt"],
            StuScore.is_deleted == False,  # noqa: E712
        )
        .first()
    )
    if exists:
        raise ConflictError("该学生此轮次成绩已存在")

    # 未显式指定等级时，根据分数自动判定
    if not data.get("score_level"):
        data["score_level"] = compute_score_level(data["exam_score"])

    score = StuScore(**data)
    db.add(score)
    db.commit()
    db.refresh(score)
    return score


def update_score(db: Session, score_id: int, data: dict) -> StuScore:
    """更新成绩：若更换学生需校验存在；只改分数没改等级时自动重判等级。"""
    score = assert_score_alive(db, score_id)

    if data.get("stu_id"):
        assert_stu_alive(db, data["stu_id"])

    if "exam_score" in data and "score_level" not in data:
        data["score_level"] = compute_score_level(data["exam_score"])

    for field, value in data.items():
        setattr(score, field, value)

    db.commit()
    db.refresh(score)
    return score


def soft_delete_score(db: Session, score_id: int) -> None:
    """软删除成绩记录。"""
    score = assert_score_alive(db, score_id)
    score.is_deleted = True
    db.commit()