const MS_MINUTE = 60_000;
const MS_HOUR = 60 * MS_MINUTE;
const MS_DAY = 24 * MS_HOUR;

function shanghaiParts(input: string | Date) {
  const d = input instanceof Date ? input : new Date(input);
  if (Number.isNaN(d.getTime())) return null;
  const sh = new Date(d.getTime() + 8 * 60 * 60 * 1000);
  const p = (n: number) => String(n).padStart(2, '0');
  return {
    year: sh.getUTCFullYear(),
    month: p(sh.getUTCMonth() + 1),
    day: p(sh.getUTCDate()),
    hour: p(sh.getUTCHours()),
    minute: p(sh.getUTCMinutes()),
  };
}

/** 核销走马灯时间：24 小时内相对时间，超过则显示具体时间 */
export function formatRedeemRelativeTime(input?: string | Date | null): string {
  if (input == null || input === '') return '刚刚';
  const at = input instanceof Date ? input : new Date(input);
  if (Number.isNaN(at.getTime())) return '刚刚';
  const diffMs = Date.now() - at.getTime();
  if (diffMs < MS_MINUTE) return '刚刚';
  if (diffMs < MS_HOUR) return `${Math.floor(diffMs / MS_MINUTE)}分钟前`;
  if (diffMs < MS_DAY) return `${Math.floor(diffMs / MS_HOUR)}小时前`;
  const parts = shanghaiParts(at);
  if (!parts) return '刚刚';
  const nowParts = shanghaiParts(new Date());
  const datePrefix =
    nowParts && parts.year === nowParts.year
      ? `${parts.month}-${parts.day}`
      : `${parts.year}-${parts.month}-${parts.day}`;
  return `${datePrefix} ${parts.hour}:${parts.minute}`;
}

/** 格式化为 Asia/Shanghai：2026-08-03 15:14:30（不依赖 Intl，兼容微信小程序） */
export function formatShanghaiDateTime(input?: string | Date | null): string {
  if (input == null || input === '') return '—';
  if (typeof input === 'string') {
    const s = input.trim();
    if (/^\d{4}-\d{2}-\d{2}[ T]\d{2}:\d{2}/.test(s)) {
      return s.slice(0, 19).replace('T', ' ');
    }
  }
  const d = input instanceof Date ? input : new Date(input);
  if (Number.isNaN(d.getTime())) return '—';
  // 用 UTC 读数 + 固定东八区偏移，避免依赖 Intl / 设备时区 API 差异
  const sh = new Date(d.getTime() + 8 * 60 * 60 * 1000);
  const p = (n: number) => String(n).padStart(2, '0');
  return `${sh.getUTCFullYear()}-${p(sh.getUTCMonth() + 1)}-${p(sh.getUTCDate())} ${p(sh.getUTCHours())}:${p(sh.getUTCMinutes())}:${p(sh.getUTCSeconds())}`;
}