"""统一响应与业务异常（对齐《03-接口文档》1.2 统一响应结构）"""
import uuid
from contextvars import ContextVar
from typing import Any

from fastapi import FastAPI, Request
from fastapi.exceptions import RequestValidationError
from fastapi.responses import JSONResponse

from app.core import errors

# 请求链路 ID（中间件写入，日志/响应共用）
request_id_ctx: ContextVar[str] = ContextVar("request_id", default="")


def ok(data: Any = None, message: str = "ok") -> dict:
    return {
        "code": errors.OK,
        "message": message,
        "data": data if data is not None else {},
        "request_id": request_id_ctx.get() or str(uuid.uuid4()),
    }


class BizException(Exception):
    """业务异常：抛出后由全局处理器转为统一响应"""

    def __init__(self, code: int, message: str | None = None, http_status: int = 200, data: dict | None = None):
        self.code = code
        self.message = message or errors.DEFAULT_MESSAGES.get(code, "error")
        self.http_status = http_status
        self.data = data or {}


def _fail_body(code: int, message: str, data: dict | None = None) -> dict:
    return {
        "code": code,
        "message": message,
        "data": data or {},
        "request_id": request_id_ctx.get() or str(uuid.uuid4()),
    }


def register_exception_handlers(app: FastAPI) -> None:
    @app.exception_handler(BizException)
    async def biz_handler(request: Request, exc: BizException) -> JSONResponse:
        return JSONResponse(status_code=exc.http_status, content=_fail_body(exc.code, exc.message, exc.data))

    @app.exception_handler(RequestValidationError)
    async def validation_handler(request: Request, exc: RequestValidationError) -> JSONResponse:
        return JSONResponse(
            status_code=200,
            content=_fail_body(errors.PARAM_ERROR, f"参数错误: {exc.errors()[0].get('msg', '')}"),
        )

    @app.exception_handler(Exception)
    async def unhandled_handler(request: Request, exc: Exception) -> JSONResponse:
        return JSONResponse(status_code=500, content=_fail_body(errors.INTERNAL_ERROR, "服务器内部错误"))