import os
from typing import Optional

import pandas as pd
import tushare as ts


def _init_api():
    token = os.environ.get("TUSHARE_TOKEN")
    if not token:
        raise RuntimeError("TUSHARE_TOKEN 环境变量未设置")
    ts.set_token(token)
    return ts.pro_api()


def fetch_contract(ts_code: str, limit: int = 100) -> pd.DataFrame:
    """拉取指定期货合约的日线数据,返回按 trade_date 升序排列的 DataFrame。"""
    pro = _init_api()
    df = pro.fut_daily(ts_code=ts_code)

    if df.empty:
        raise RuntimeError(f"未返回 {ts_code} 的任何数据,可能合约代码错误或 token 积分不足")

    cols = [
        "ts_code", "trade_date", "open", "high", "low",
        "close", "vol", "amount", "oi", "oi_chg", "pre_close",
    ]
    df = df[[c for c in cols if c in df.columns]].copy()

    numeric = ["open", "high", "low", "close", "vol", "amount", "oi", "oi_chg", "pre_close"]
    for c in numeric:
        if c in df.columns:
            df[c] = pd.to_numeric(df[c], errors="coerce")

    df = df.sort_values("trade_date").reset_index(drop=True)
    return df