# dao/cls_mgmt_dao.py
# 班级管理数据访问层

from typing import List, Optional, Tuple

from sqlalchemy.orm import Session

from dao.exceptions import ConflictError, NotFoundError
from dao.pagination import paginate
from dao.teacher_dao import assert_teacher_alive
from model.cls_mgmt_model import ClsMgmt


def assert_cls_alive(db: Session, cls_id: str, detail: Optional[str] = None) -> ClsMgmt:
    """
    确认班级存在且未删除，否则抛 NotFoundError。
    供学生模块复用作外键校验。
    """
    cls = db.query(ClsMgmt).filter(ClsMgmt.id == cls_id, ClsMgmt.is_deleted == 0).first()
    if not cls:
        raise NotFoundError(detail or f"班级 {cls_id} 不存在")
    return cls


def list_classes(
    db: Session,
    page: int,
    size: int,
    head_tea_id: Optional[str] = None,
    lecturer_id: Optional[str] = None,
) -> Tuple[int, List[ClsMgmt]]:
    """分页查询班级，支持按班主任 / 主讲老师过滤。"""
    query = db.query(ClsMgmt).filter(ClsMgmt.is_deleted == 0)
    if head_tea_id:
        query = query.filter(ClsMgmt.head_tea_id == head_tea_id)
    if lecturer_id:
        query = query.filter(ClsMgmt.lecturer_id == lecturer_id)
    return paginate(query, page, size, order_by=ClsMgmt.id)


def create_class(db: Session, data: dict) -> ClsMgmt:
    """新增班级：校验编号唯一，且班主任与主讲老师都存在。"""
    # 编号是主键，已软删除的记录同样占用该编号，所以这里不加 is_deleted 过滤
    if db.query(ClsMgmt).filter(ClsMgmt.id == data["id"]).first():
        raise ConflictError("班级编号已存在")

    for tea_id in (data["head_tea_id"], data["lecturer_id"]):
        assert_teacher_alive(db, tea_id)

    cls = ClsMgmt(**data)
    db.add(cls)
    db.commit()
    db.refresh(cls)
    return cls


def update_class(db: Session, cls_id: str, data: dict) -> ClsMgmt:
    """更新班级：若更换教师需重新校验教师存在。"""
    cls = assert_cls_alive(db, cls_id, "班级不存在或已删除")

    for field in ("head_tea_id", "lecturer_id"):
        if data.get(field):
            assert_teacher_alive(db, data[field])

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

    db.commit()
    db.refresh(cls)
    return cls


def soft_delete_class(db: Session, cls_id: str) -> None:
    """软删除班级。"""
    cls = assert_cls_alive(db, cls_id, "班级不存在或已删除")
    cls.is_deleted = 1
    db.commit()