import json

import requests
from dataclasses import dataclass
from typing import Optional


@dataclass
class DraftResult:
    media_id: str


def create_draft(
    access_token: str,
    title: str,
    html: str,
    digest: str,
    thumb_media_id: Optional[str] = None,
    author: Optional[str] = None,
) -> DraftResult:
    """
    Create a draft in WeChat.
    API: POST https://api.weixin.qq.com/cgi-bin/draft/add
    Returns DraftResult.
    Raise ValueError on error (errcode present and != 0).
    """
    article = {
        "title": title,
        "author": author or "",
        "digest": digest,
        "content": html,
        "show_cover_pic": 0,
    }

    # thumb_media_id is required by WeChat API — if not provided,
    # upload a default 1x1 white pixel, or skip if truly empty
    if thumb_media_id:
        article["thumb_media_id"] = thumb_media_id

    body = {"articles": [article]}

    # MUST use ensure_ascii=False — otherwise Chinese becomes \uXXXX
    # and WeChat stores the escape sequences literally, causing title
    # length overflow and garbled content.
    resp = requests.post(
        "https://api.weixin.qq.com/cgi-bin/draft/add",
        params={"access_token": access_token},
        data=json.dumps(body, ensure_ascii=False).encode("utf-8"),
        headers={"Content-Type": "application/json; charset=utf-8"},
    )

    data = resp.json()

    errcode = data.get("errcode", 0)
    if errcode != 0:
        errmsg = data.get("errmsg", "unknown error")
        raise ValueError(f"WeChat create_draft error: errcode={errcode}, errmsg={errmsg}")

    if "media_id" not in data:
        raise ValueError(f"WeChat create_draft error: missing media_id in response: {data}")

    return DraftResult(media_id=data["media_id"])