from sqlalchemy.orm import Session
from core import database
from models.teacher import Teacher
from models.class_teacher import ClassTeachers
from schemas.teacher import TeacherUpdate, TeacherCreate,ClassTeachersCreate
from utils.code_generator import generate_no
from fastapi import HTTPException

'''
本文件内容为老师表与班级老师关系表的增删改查函数集合
'''
#=================老师表Teacher的CRUD================
#查询所有未被删除的老师
def get_teacher_list(db:Session):
    #查询老师列表，过滤逻辑删除
    return db.query(Teacher).filter(Teacher.is_deleted == 0).all()
#根据id,查询单个符合条件的老师
def get_teacher_by_id(db:Session,teacher_id:int,):
    return db.query(Teacher).filter(Teacher.id == teacher_id
                                    ,Teacher.is_deleted == 0).first()
#新增
def create_teacher(db:Session,obj:TeacherCreate):
    '''
    新增
    :param db: Session 数据库会话
    :param obj:TeacherCreate 前端传入新增数据
    :return: db_teacher 新增成功的ORM对象
    业务逻辑：
        1、查重：同名有效老师不能重复新增
        2、如果前端手动添加teacher_no，校验编号不能和已有有效老师编号重复
        3、创建ORM对象加入会话
        4、调用generate_no，走动生成业务编号
        5、commit提交事务入库，refresh刷新对象
    '''
    exist_teacher = db.query(Teacher).filter(Teacher.teacher_name == obj.teacher_name
                                             ,Teacher.is_deleted == 0).first()
    if exist_teacher:
        raise HTTPException(status_code=409,detail='该用户已存在')
    if obj.teacher_no:
        exist_teacher = db.query(Teacher).filter(Teacher.teacher_no == obj
                                                 .teacher_no,Teacher.is_deleted == 0).first()
        if exist_teacher:
            raise HTTPException(status_code=409,detail='老师编号已存在')
    #开始添加
    data = obj.model_dump(exclude_none=True)
    db_teacher = Teacher(**data)
    db.add(db_teacher)
    # 调用公共函数生成业务编号，内部执行db.flush拿到自增id
    generate_no('teacher_no','TCH',db_teacher,db)
    db.commit()
    db.refresh(db_teacher)
    #从数据库重新查询这条记录，刷新 db_teacher 对象。
    #作用：同步数据库默认字段的值，例如`created_at`、`updated_at`，拿到数据库里最新的数据，
    # 最终返回给前端。
    return db_teacher
#更新
def update_teacher(db:Session,teacher_id:int,obj:TeacherUpdate):
    """
        修改老师信息，局部更新
        :param db: Session 数据库会话
        :param teacher_id: int 需要修改的老师id
        :param obj: TeacherUpdate 前端传入要修改的字段
        :return: db_teacher ORM对象 / None
    """
    # 调用get_teacher_by_id校验用户是否存在
    db_teacher = get_teacher_by_id(db,teacher_id)
    if obj.teacher_name:
        exist_teacher = db.query(Teacher).filter(
            Teacher.teacher_name == obj.teacher_name,
            Teacher.id != teacher_id,
            Teacher.is_deleted == 0
        ).first()
        if exist_teacher:
            raise HTTPException(status_code=409, detail="该姓名已被其他老师占用！")
    if obj.teacher_no:
        exist_no = db.query(Teacher).filter(
            Teacher.teacher_no == obj.teacher_no,
            Teacher.id != teacher_id,
            Teacher.is_deleted == 0
        ).first()
        if exist_no:
            raise HTTPException(status_code=409, detail="老师编号已被其他老师占用！")
    #用户存在，解析键值对，循环使用setattr添加
    update_data = obj.model_dump(exclude_none=True)
    for k, v in update_data.items():
        setattr(db_teacher, k, v)
    db.commit()
    db.refresh(db_teacher)
    return db_teacher
#删除
def delete_teacher(db:Session,teacher_id:int):
    """
        逻辑删除老师，不是物理删除；修改is_deleted=1
        :param db: Session
        :param teacher_id:老师主键id
        :return: Teacher ORM对象，找不到返回None
        业务限制：老师已经分配班级，则不允许删除，防止脏数据
    """
    # 查询目标老师
    db_teacher = get_teacher_by_id(db, teacher_id)
    if not db_teacher:
        return None

    # 校验：查询班级老师中间表，判断该老师是否还有有效带班关系
    rel = db.query(ClassTeachers).filter(
        ClassTeachers.teacher_id == teacher_id,
        ClassTeachers.is_deleted == 0
    ).first()
    if rel:
        raise HTTPException(
            status_code=400,
            detail="该老师已分配班级，不能删除，请先解除带班关系！"
        )

    # 逻辑删除标记
    db_teacher.is_deleted = 1
    db.commit()
    return db_teacher

#==================班级老师中间表 CRUD=====================
#查询
def get_class_teacher_by_class_id(db: Session, class_id: int):
    """
    根据班级id，查询该班级所有有效的带班老师关系
    :param db: Session
    :param class_id:班级主键
    :return: list[ClassTeacher]
    """
    return (
        db.query(ClassTeachers)
        .filter(ClassTeachers.class_id == class_id
                ,ClassTeachers.is_deleted == 0)
        .all()
    )

#新增
def create_class_teacher(db: Session, obj: ClassTeachersCreate):
    """
    分配老师到班级，新增班级-老师关系记录
    :param db: Session
    :param obj: ClassTeacherCreate class_id、teacher_id、role
    :return: ClassTeacher ORM对象
    校验：
        1.老师必须存在且未删除
        2.同一班级同一个老师同一个角色不能重复分配
    """
    # 校验老师是否存在
    teacher = get_teacher_by_id(db, obj.teacher_id)
    if not teacher:
        raise HTTPException(status_code=404, detail="老师不存在或已删除！")

    # 查重：同一班级+同一老师+同一角色不能重复分配
    rel = db.query(ClassTeachers).filter(
        ClassTeachers.class_id == obj.class_id,
        ClassTeachers.teacher_id == obj.teacher_id,
        ClassTeachers.role == obj.role,
        ClassTeachers.is_deleted == 0
    ).first()
    if rel:
        raise HTTPException(status_code=409, detail="该老师已以相同角色分配到该班级！")

    data = obj.model_dump()
    db_obj = ClassTeachers(**data)
    db.add(db_obj)
    db.commit()
    db.refresh(db_obj)

    return db_obj

#更新
def update_class_teacher_full(db: Session, rel_id: int, obj: ClassTeachersCreate):
    """
    完整更新班级老师关系：可修改 class_id、teacher_id、role
    :param db: Session
    :param rel_id: 中间表主键
    :param obj: ClassTeacherCreate 传入的新参数
    :return: ClassTeacher ORM对象
    校验：
        1. 关系记录存在且未删除
        2. 如果修改teacher_id，校验老师必须有效存在
        3. 校验新组合(class_id+teacher_id+role)不能和其他有效记录重复
    """
    # 1. 查询原有记录
    db_rel = db.query(ClassTeachers).filter(
        ClassTeachers.id == rel_id,
        ClassTeachers.is_deleted == 0
    ).first()
    if not db_rel:
        return None

    # 2. 如果老师ID发生变化，校验老师是否有效
    if obj.teacher_id != db_rel.teacher_id:
        teacher = get_teacher_by_id(db, obj.teacher_id)
        if not teacher:
            raise HTTPException(status_code=404, detail="老师不存在或已删除！")

    # 3. 查重：新的三元组合不能重复（排除自身这条记录）
    exist_rel = db.query(ClassTeachers).filter(
        ClassTeachers.class_id == obj.class_id,
        ClassTeachers.teacher_id == obj.teacher_id,
        ClassTeachers.role == obj.role,
        ClassTeachers.is_deleted == 0,
        ClassTeachers.id != rel_id
    ).first()
    if exist_rel:
        raise HTTPException(status_code=409, detail="该老师已以相同角色分配到该班级！")

    # 赋值更新
    db_rel.class_id = obj.class_id
    db_rel.teacher_id = obj.teacher_id
    db_rel.role = obj.role

    db.commit()
    db.refresh(db_rel)
    return db_rel


#删除
def delete_class_teacher(db: Session, rel_id: int):
    """
    逻辑删除班级老师带班关系
    :param db: Session
    :param rel_id: class_teachers表主键id
    :return: ClassTeacher ORM对象，找不到返回None
    """
    db_obj = (
        db.query(ClassTeachers)
        .filter(ClassTeachers.id == rel_id, ClassTeachers.is_deleted == 0)
        .first()
    )
    if not db_obj:
        return None

    db_obj.is_deleted = 1
    db.commit()
    return db_obj