"""币安 U 本位合约模拟盘（Demo Trading）签名客户端

只连模拟盘：地址写死，没有切换实盘的参数，避免误下真单。
"""

import hashlib
import hmac
import time
from typing import Any
from urllib.parse import urlencode

import httpx

BASE_URL = "https://demo-fapi.binance.com"
RECV_WINDOW_MS = 5000
TIMEOUT_SECONDS = 10


class ExchangeError(Exception):
    """交易所或网络错误；code 为币安错误码（如 -2021），网络层错误时 status、code 为空"""

    def __init__(self, status: int | None, code: int | None, message: str) -> None:
        super().__init__(f"{status} {code}: {message}")
        self.status = status
        self.code = code
        self.message = message

    @property
    def retryable(self) -> bool:
        # 只有限流、服务端错误、-1001（内部断连）可以重试；业务错误重试也不会成功
        return self.status in (418, 429) or (self.status or 0) >= 500 or self.code == -1001

    def __str__(self) -> str:
        if self.status is None:
            return self.message
        return f"币安返回 {self.status}（{self.code}）：{self.message}"


class DemoClient:
    def __init__(self, api_key: str, api_secret: str) -> None:
        self.secret = api_secret.encode()
        self.http = httpx.AsyncClient(base_url=BASE_URL, timeout=TIMEOUT_SECONDS, headers={"X-MBX-APIKEY": api_key})
        # 本地时钟与服务器的偏差（毫秒），遇到 -1021 时校准
        self.time_offset = 0

    async def __aenter__(self) -> "DemoClient":
        return self

    async def __aexit__(self, *_: object) -> None:
        await self.http.aclose()

    async def sync_time(self) -> None:
        server_time = (await self.request("GET", "/fapi/v1/time", signed=False))["serverTime"]
        self.time_offset = server_time - int(time.time() * 1000)

    async def request(self, method: str, path: str, params: dict[str, Any] | None = None, signed: bool = True) -> Any:
        """不自动重试：下单类请求重发可能重复成交，由调用方按 clientOrderId 查询后决定"""
        for attempt in range(2):
            # 币安要求布尔参数为小写字符串
            query = {k: str(v).lower() if isinstance(v, bool) else v for k, v in (params or {}).items() if v is not None}
            if signed:
                query["timestamp"] = int(time.time() * 1000) + self.time_offset
                query["recvWindow"] = RECV_WINDOW_MS
            encoded = urlencode(query)
            if signed:
                encoded += "&signature=" + hmac.new(self.secret, encoded.encode(), hashlib.sha256).hexdigest()
            try:
                resp = await self.http.request(method, f"{path}?{encoded}" if encoded else path)
            except httpx.TransportError as e:
                raise ExchangeError(None, None, f"无法连接币安模拟盘：{e!r}") from e
            if resp.status_code < 400:
                return resp.json()
            try:
                body = resp.json()
            except ValueError:
                body = {}
            code = body.get("code") if isinstance(body, dict) else None
            # 时间戳超出接收窗口时请求未被受理，校准时钟后重发是安全的
            if code == -1021 and attempt == 0:
                await self.sync_time()
                continue
            raise ExchangeError(resp.status_code, code, body.get("msg", resp.text[:200]) if isinstance(body, dict) else resp.text[:200])
        raise AssertionError("unreachable")