"""统一响应包。

Success:  {"code": 0, "msg": "ok", "data": ...}
Failure:  {"code": 404, "msg": "学生不存在", "data": null}
code=0 表示成功，其余为业务错误码（与 HTTP 状态码对齐，前端可统一判断 code !== 0）。
"""

from __future__ import annotations

from typing import Any, Generic, TypeVar

from pydantic import BaseModel, Field

T = TypeVar("T")


class Resp(BaseModel, Generic[T]):
    code: int = Field(0, description="0=成功，非 0=业务错误码")
    msg: str = Field("ok", description="提示信息")
    data: T | None = Field(None, description="业务数据")

    @classmethod
    def ok(cls, data: Any = None, msg: str = "ok") -> dict:
        return {"code": 0, "msg": msg, "data": data}

    @classmethod
    def fail(cls, msg: str, code: int = 400, data: Any = None) -> dict:
        return {"code": code, "msg": msg, "data": data}


def ok(data: Any = None, msg: str = "ok") -> dict:
    """最常用的写法：return ok(result)"""
    return {"code": 0, "msg": msg, "data": data}