"""业务窗时钟：16:00 开 → 08:00 停开；轮次与休息。"""

from __future__ import annotations

from datetime import datetime, timedelta
from zoneinfo import ZoneInfo

_SH = ZoneInfo("Asia/Shanghai")


def now_sh(now: datetime | None = None) -> datetime:
    return (now or datetime.now(tz=_SH)).astimezone(_SH)


def parse_hhmm(s: str) -> tuple[int, int]:
    parts = (s or "16:00").strip().split(":")
    return int(parts[0]), int(parts[1]) if len(parts) > 1 else 0


def window_key(now: datetime | None = None) -> str:
    """
    业务窗键：若当前 >= 当日 16:00，窗从今日 16:00 起，键=今日日期；
    若 < 16:00，仍可能属于「昨日起的窗」（到今日 08:00），键=昨日。
    """
    n = now_sh(now)
    open_h, open_m = 16, 0
    stop_h, stop_m = 8, 0
    today_open = n.replace(hour=open_h, minute=open_m, second=0, microsecond=0)
    today_stop = n.replace(hour=stop_h, minute=stop_m, second=0, microsecond=0)
    if n >= today_open:
        return n.strftime("%Y%m%d")
    if n < today_stop:
        # 仍在昨 16:00 开启的窗内
        return (n.date() - timedelta(days=1)).strftime("%Y%m%d")
    # 08:00～16:00：不在开仓窗，键用「即将开始」的今日窗
    return n.strftime("%Y%m%d")


def can_open_new(
    now: datetime | None = None,
    *,
    open_hhmm: str = "16:00",
    stop_hhmm: str = "08:00",
) -> bool:
    n = now_sh(now)
    oh, om = parse_hhmm(open_hhmm)
    sh, sm = parse_hhmm(stop_hhmm)
    today_open = n.replace(hour=oh, minute=om, second=0, microsecond=0)
    today_stop = n.replace(hour=sh, minute=sm, second=0, microsecond=0)
    if n >= today_open:
        return True
    if n < today_stop:
        return True
    return False


def group_date_ymd(now: datetime | None = None) -> str:
    return window_key(now)