"""按自然日（YYYY-MM-DD）解析为 [day_start, day_end) 的 create_time 筛选条件。"""

from datetime import datetime, timedelta


def current_month_bounds(now: datetime | None = None) -> tuple[datetime, datetime]:
    """当前自然月 [month_start, next_month_start)，与服务器本地时间一致（项目约定 Asia/Shanghai）。"""
    if now is None:
        now = datetime.now()
    month_start = now.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
    if now.month == 12:
        month_end = datetime(now.year + 1, 1, 1)
    else:
        month_end = datetime(now.year, now.month + 1, 1)
    return month_start, month_end


def parse_create_time_day_bounds(apply_date: str | None) -> tuple[datetime, datetime] | None:
    if not apply_date or not str(apply_date).strip():
        return None
    try:
        day_start = datetime.strptime(str(apply_date).strip(), "%Y-%m-%d")
        return day_start, day_start + timedelta(days=1)
    except ValueError:
        return None


def resolve_apply_create_time(apply_date: str | None, now: datetime | None = None) -> datetime:
    """申请日 YYYY-MM-DD → create_time；当天用当前时刻，其它日期用当日 0 点。"""
    if now is None:
        now = datetime.now()
    bounds = parse_create_time_day_bounds(apply_date)
    if not bounds:
        return now
    day_start, _ = bounds
    if day_start.date() == now.date():
        return now
    return day_start