"""领券业务透传端点。

把客户端的 POST /api/v1/coupon/step 请求原样转发给 pricebot-backend
的 /api/coupon/step。MVP 阶段**不鉴权**(见 docs/待办与技术债.md P1:
device_id 透传给 pricebot 区分设备,待补 JWT + device_id↔user_id 绑定后
才能做用户级画像)。

pricebot 协议文档:
  pricebot-backend/docs/projects/领券-客户端对接协议.md
"""
from __future__ import annotations

import json
import logging
from typing import Any

import httpx
from fastapi import APIRouter, HTTPException, Request, status

from app.core.config import settings
from app.core.pricebot_router import pick_pricebot

logger = logging.getLogger("shagua.coupon")

router = APIRouter(prefix="/api/v1/coupon", tags=["coupon"])


@router.post("/step", summary="领券任务步进 (透传到 pricebot)")
async def coupon_step(
    request: Request,
) -> dict[str, Any]:
    """把请求体原样转发给 pricebot-backend 的 /api/coupon/step。

    - 鉴权: MVP 阶段不鉴权(待补 JWT,见 docs/待办与技术债.md P1)
    - 透传: 不做 schema 校验,pricebot 自己校验
    - 失败: 网络不可达 / pricebot 5xx → 502 + 友好 message
    """
    # 读原始字节,避免"反序列化→再序列化"的双重 JSON(省透传 CPU)。只 loads 一次拿
    # trace_id 做亲和 + 打日志,转发时直接发原始 bytes,不重新 dumps。
    raw = await request.body()
    try:
        meta = json.loads(raw)
    except Exception as e:
        raise HTTPException(status_code=400, detail=f"invalid json body: {e}") from e
    if not isinstance(meta, dict):
        meta = {}

    # 按 trace_id 一致性 hash 选 pricebot 实例(同一领券任务的所有帧落同一进程)
    base = pick_pricebot(meta.get("trace_id"))
    url = f"{base.rstrip('/')}/api/coupon/step"
    timeout = settings.PRICEBOT_REQUEST_TIMEOUT_SEC

    logger.info(
        "coupon_step device_id=%s trace_id=%s step=%s",
        meta.get("device_id"),
        meta.get("trace_id"),
        meta.get("step"),
    )

    try:
        async with httpx.AsyncClient(timeout=timeout) as client:
            resp = await client.post(
                url, content=raw, headers={"Content-Type": "application/json"}
            )
    except httpx.RequestError as e:
        logger.error("[pricebot] request failed: %s", e)
        raise HTTPException(
            status_code=status.HTTP_502_BAD_GATEWAY,
            detail=f"pricebot upstream unreachable: {e}",
        ) from e

    if resp.status_code >= 500:
        logger.error(
            "[pricebot] 5xx status=%d body=%s",
            resp.status_code,
            resp.text[:500],
        )
        raise HTTPException(
            status_code=status.HTTP_502_BAD_GATEWAY,
            detail=f"pricebot upstream returned {resp.status_code}",
        )

    return resp.json()