"""公开行情辅助：补历史到期结算指数展示（不发明成交现金）。"""

from __future__ import annotations

import json
import logging
import urllib.error
import urllib.request
from typing import Any

logger = logging.getLogger(__name__)

_CACHE: dict[int, float] = {}
_CACHE_MAX = 256


def looks_binance_option(inst_id: str | None) -> bool:
    return "USD_UM" in str(inst_id or "")


def eth_usdt_close_at_ms(ts_ms: int | None) -> float | None:
    """币安 ETHUSDT 1m K 线收盘价（近似期权结算指数）。失败返回 None。"""
    if ts_ms is None:
        return None
    try:
        ms = int(ts_ms)
    except (TypeError, ValueError):
        return None
    if ms <= 0:
        return None
    minute = (ms // 60_000) * 60_000
    cached = _CACHE.get(minute)
    if cached is not None:
        return cached
    url = (
        "https://api.binance.com/api/v3/klines"
        f"?symbol=ETHUSDT&interval=1m&startTime={minute}&limit=1"
    )
    try:
        with urllib.request.urlopen(url, timeout=4) as resp:
            raw = resp.read().decode("utf-8", "replace")
        rows = json.loads(raw)
        if not rows:
            return None
        close_px = float(rows[0][4])
        if close_px <= 0:
            return None
        if len(_CACHE) >= _CACHE_MAX:
            _CACHE.clear()
        _CACHE[minute] = close_px
        return close_px
    except (urllib.error.URLError, TimeoutError, ValueError, TypeError, IndexError) as e:
        logger.debug("eth_usdt_close_at_ms failed ms=%s: %s", minute, e)
        return None


def maybe_public_settle_index(g: dict[str, Any]) -> float | None:
    """库内无结算价时，币安期权到期组用公开 ETHUSDT 收盘近似。"""
    if str(g.get("close_reason") or "") != "expiry":
        return None
    inst = g.get("option_inst_id") or g.get("option2_inst_id")
    if not looks_binance_option(str(inst) if inst else None):
        return None
    ts = g.get("close_at_ms") or g.get("hold_close_at_ms")
    return eth_usdt_close_at_ms(ts if ts is not None else None)