from sqlalchemy.orm import Session
from models.employment import Employment
from schemas.employment import EmploymentCreate, EmploymentUpdate, EmploymentResponse


def create_employment(db, obj_in):
    """新增就业信息：一个学生只能存在一条就业记录"""
    try:
        # obj_in.model_dump()把pydantic请求对象转为字典，解包传给Employment生成ORM对象
        db_obj = Employment(**obj_in.model_dump())
        # add：把对象加入数据库会话，此时还没写入数据库
        db.add(db_obj)
        # commit：提交事务，真正写入mysql数据库
        db.commit()
        # refresh：从数据库刷新对象，拿到数据库自动生成的id、默认时间等字段
        db.refresh(db_obj)
        # model_validate：把sqlalchemy ORM对象解析进pydantic响应模型
        # model_dump：把pydantic模型转为普通python字典返回给上层api
        return EmploymentResponse.model_validate(db_obj).model_dump()
    except Exception:
        # 发生任何异常，执行回滚，撤销本次会话中未提交的数据库改动
        db.rollback()
        # 异常情况返回None，上层api可以判断新增失败
        return None


def get_employment_by_id(db, eid):
    """根据主键id查询就业详情，过滤逻辑删除"""
    try:
        db_obj = db.query(Employment).filter(
            Employment.id == eid,
            Employment.is_deleted == 0
        ).first()
        if not db_obj:
            return None
        return EmploymentResponse.model_validate(db_obj).model_dump()
    except Exception:
        return None


def get_employment_by_student_id(db, student_id):
    """根据学生id查询就业信息，过滤逻辑删除"""
    try:
        db_obj = db.query(Employment).filter(
            Employment.student_id == student_id,
            Employment.is_deleted == 0
        ).first()
        if not db_obj:
            return None
        return EmploymentResponse.model_validate(db_obj).model_dump()
    except Exception:
        return None


def get_employment_list(db, company_name=None, salary_min=None, salary_max=None, skip=0, limit=20):
    """就业列表查询；支持公司名模糊、薪资范围筛选；只查询is_deleted=0"""
    try:
        query = db.query(Employment).filter(Employment.is_deleted == 0)
        if company_name:
            query = query.filter(Employment.company_name.like(f"%{company_name}%"))
        if salary_min is not None:
            query = query.filter(Employment.salary >= salary_min)
        if salary_max is not None:
            query = query.filter(Employment.salary <= salary_max)
        # count()统计满足条件总条数，用于分页total
        total = query.count()
        # offset偏移量（跳过多少条），limit每页多少条，执行查询拿到结果列表
        records = query.offset(skip).limit(limit).all()
        # 列表推导式：循环每一条ORM记录，全部转为字典，得到字典列表
        dict_list = [EmploymentResponse.model_validate(item).model_dump() for item in records]
        # 返回字典列表 + 总条数
        return dict_list, total
    except Exception:
        # 异常返回空列表，总条数0
        return [], 0


def update_employment(db, eid, obj_in):
    """修改就业信息，只更新传入的字段"""
    try:
        # 根据id查询未删除的记录
        db_obj_raw = db.query(Employment).filter(
            Employment.id == eid,
            Employment.is_deleted == 0
        ).first()
        # 记录不存在直接返回None
        if db_obj_raw is None:
            return None
        # exclude_unset=True：只取出前端实际传过来的字段，不会带上没传的None字段
        update_dict = obj_in.model_dump(exclude_unset=True)
        for key, value in update_dict.items():
            setattr(db_obj_raw, key, value)
        db.commit()
        db.refresh(db_obj_raw)
        return EmploymentResponse.model_validate(db_obj_raw).model_dump()
    except Exception:
        db.rollback()
        return None


def delete_employment_logic(db, eid):
    """逻辑删除，只修改is_deleted=1，不做物理删除"""
    try:
        db_obj_raw = db.query(Employment).filter(
            Employment.id == eid,
            Employment.is_deleted == 0
        ).first()
        if db_obj_raw is None:
            return False
        db_obj_raw.is_deleted = 1
        db.commit()
        return True
    except Exception:
        db.rollback()
        return False