try:
    user_id = await get_user()
    post_id = params_kw.get('post_id', '')

    db = DBPools()
    async with db.sqlorContext('sage') as sor:
        # 检查作品是否存在且为付费KTV
        posts = await sor.R('showcase_posts', {"id": post_id})
        if not posts:
            return json.dumps({"status": "error", "message": "作品不存在"}, ensure_ascii=False)

        post = posts[0]
        price = float(post.get('price', 0))
        if price <= 0:
            return json.dumps({"status": "error", "message": "该作品免费，无需购买"}, ensure_ascii=False)

        # 检查是否已购买
        existing = await sor.sqlExe(
            "SELECT id FROM showcase_downloads WHERE post_id = ${post_id}$ AND user_id = ${user_id}$ AND payment_status = '1'",
            {"post_id": post_id, "user_id": user_id}
        )
        if existing:
            return json.dumps({"status": "ok", "message": "已购买", "download_url": post.get('content_url', '')}, ensure_ascii=False)

        # 创建购买记录(模拟支付成功)
        dl_data = {
            "post_id": post_id,
            "user_id": user_id,
            "price": price,
            "payment_status": "1",
            "download_url": post.get('content_url', ''),
            "download_count": 1,
            "created_at": curDateString()
        }
        result = await create_showcase_download(dl_data)
        return json.dumps({"status": "ok", "message": "购买成功", "download_url": post.get('content_url', '')}, ensure_ascii=False)
except Exception as e:
    return json.dumps({"status": "error", "message": str(e)}, ensure_ascii=False)