"""列表/导出用 UTC 时间窗（Gate / Binance 主站共用）。"""

from datetime import datetime, timedelta, timezone

PRESET_UTC_TODAY = "utc_today"
PRESET_UTC_LAST24H = "utc_last24h"
PRESET_UTC_LAST7D = "utc_last7d"
PRESET_CUSTOM = "custom"


def utc_now():
    return datetime.now(timezone.utc)


def utc_today_bounds(now=None):
    now = now or utc_now()
    start = now.replace(hour=0, minute=0, second=0, microsecond=0)
    return start, now


def resolve_window(query_mapping, default_preset=PRESET_UTC_TODAY):
    """
    从 ?win_preset= & from_utc= & to_utc= 解析窗口。
    返回 dict: preset, start_utc, end_utc, label, start_ms, end_ms
    """
    preset = (query_mapping.get("win_preset") or default_preset or PRESET_UTC_TODAY).strip().lower()
    now = utc_now()

    if preset == PRESET_UTC_LAST24H:
        start = now - timedelta(hours=24)
        end = now
        label = "近24小时(UTC)"
    elif preset == PRESET_UTC_LAST7D:
        start = now - timedelta(days=7)
        end = now
        label = "近7天(UTC)"
    elif preset == PRESET_CUSTOM:
        start = _parse_utc_input(query_mapping.get("from_utc")) or utc_today_bounds(now)[0]
        end = _parse_utc_input(query_mapping.get("to_utc")) or now
        if end < start:
            start, end = end, start
        label = f"{start.strftime('%Y-%m-%d %H:%M')} ~ {end.strftime('%Y-%m-%d %H:%M')} UTC"
    else:
        start, end = utc_today_bounds(now)
        preset = PRESET_UTC_TODAY
        label = f"UTC当日 {start.strftime('%Y-%m-%d')}"

    return {
        "preset": preset,
        "start_utc": start,
        "end_utc": end,
        "label": label,
        "start_ms": int(start.timestamp() * 1000),
        "end_ms": int(end.timestamp() * 1000),
    }


def _parse_utc_input(raw):
    s = (raw or "").strip().replace("T", " ").replace("Z", "").strip()
    if not s:
        return None
    for fmt, n in (("%Y-%m-%d %H:%M:%S", 19), ("%Y-%m-%d %H:%M", 16), ("%Y-%m-%d", 10)):
        try:
            dt = datetime.strptime(s[:n], fmt)
            return dt.replace(tzinfo=timezone.utc)
        except Exception:
            continue
    return None


def utc_window_to_bj_sql_strings(start_utc, end_utc, app_tz):
    """DB 存北京时间字符串时，用于 SQLite 字符串范围比较。"""
    start_bj = start_utc.astimezone(app_tz).strftime("%Y-%m-%d %H:%M:%S")
    end_bj = end_utc.astimezone(app_tz).strftime("%Y-%m-%d %H:%M:%S")
    return start_bj, end_bj