import hashlib
import json
import time
import uuid
from typing import Optional

import httpx

from config import APP_ID, TOKEN


TOKEN_URL = "https://openaiapi.weixin.qq.com/v2/token"


def _md5_hex(data: str) -> str:
    return hashlib.md5(data.encode("utf-8")).hexdigest()


async def fetch_access_token(account: Optional[str] = None) -> str:
    """
    调用微信智能对话 /v2/token 接口，换取 AccessToken。
    文档参考：https://developers.weixin.qq.com/doc/aispeech/confapi/dialog/token.html
    """
    timestamp = int(time.time())
    nonce = uuid.uuid4().hex[:16]

    body_obj = {}
    if account:
        body_obj["account"] = account
    body_str = json.dumps(body_obj, separators=(",", ":"), ensure_ascii=False)

    # sign = md5(Token + str(unix_timestamp) + nonce + md5(body))
    body_md5 = _md5_hex(body_str) if body_str else _md5_hex("")
    sign_src = f"{TOKEN}{timestamp}{nonce}{body_md5}"
    sign = _md5_hex(sign_src)

    headers = {
        "X-APPID": APP_ID,
        "request_id": str(uuid.uuid4()),
        "timestamp": str(timestamp),
        "nonce": nonce,
        "sign": sign,
        "content-type": "application/json",
    }

    async with httpx.AsyncClient(timeout=5) as client:
        resp = await client.post(TOKEN_URL, headers=headers, content=body_str.encode("utf-8"))
        resp.raise_for_status()
        data = resp.json()
        if data.get("code") != 0:
            raise RuntimeError(f"fetch_access_token error: {data}")
        return data["data"]["access_token"]