/**
 * 自动将任意精度的时间戳转换为毫秒级时间戳
 * 支持：秒(10位)、毫秒(13位)、微秒(16位)、纳秒(19位)
 */
function normalizeTimestamp(ts: number): number {
  if (ts <= 0) return ts;

  const len = Math.floor(ts).toString().length;

  if (len <= 10) {
    return ts * 1000;
  } else if (len <= 13) {
    return ts;
  } else if (len <= 16) {
    return Math.floor(ts / 1000);
  } else {
    return Math.floor(ts / 1000000);
  }
}

/**
 * 格式化时间戳为友好的显示格式（用于聊天/消息列表等）
 * - 当天、昨天：显示详细时间 HH:MM（昨天带「昨天」前缀）
 * - 大于昨天且在七天内：显示「X天前」
 * - 超过七天且本年：显示 MM/DD
 * - 非本年：显示 YY/MM/DD
 * 自动识别时间戳精度，支持秒/毫秒/微秒/纳秒级时间戳
 */
export function formatTime(ts: number): string {
  const MS = 1;
  const MINUTE = MS * 1000 * 60;
  const HOUR = MINUTE * 60;
  const DAY = HOUR * 24;

  const normalizedTs = normalizeTimestamp(ts);
  const now = Date.now();
  const diff = now - normalizedTs;

  if (diff <= 0) return '未来';
  if (diff < MINUTE) return '刚刚';

  const target = new Date(normalizedTs);
  const today = new Date(now);

  const pad = (n: number) => String(n).padStart(2, '0');
  const hm = `${pad(target.getHours())}:${pad(target.getMinutes())}`;

  const isSameDay = (a: Date, b: Date) =>
    a.getFullYear() === b.getFullYear() &&
    a.getMonth() === b.getMonth() &&
    a.getDate() === b.getDate();

  if (isSameDay(today, target)) return hm;

  const yesterday = new Date(today);
  yesterday.setDate(today.getDate() - 1);
  if (isSameDay(yesterday, target)) return `昨天 ${hm}`;

  // 按日历天数算「X天前」，避免「前天」因不足 48 小时被算成 1 天
  const todayStart = new Date(today.getFullYear(), today.getMonth(), today.getDate()).getTime();
  const targetStart = new Date(target.getFullYear(), target.getMonth(), target.getDate()).getTime();
  const calendarDaysAgo = Math.floor((todayStart - targetStart) / DAY);
  if (calendarDaysAgo >= 2 && calendarDaysAgo <= 7) return `${calendarDaysAgo}天前`;

  const MM = pad(target.getMonth() + 1);
  const DD = pad(target.getDate());
  if (target.getFullYear() !== today.getFullYear()) {
    const YY = String(target.getFullYear()).slice(-2);
    return `${YY}/${MM}/${DD}`;
  }
  return `${MM}/${DD}`;
}

/**
 * 信息流用时间格式（Feed 专用）
 * - 1 分钟内：刚刚
 * - 1 分钟～1 小时：xx分钟前
 * - 1 小时～1 天：xx小时前
 * - 1 天～1 周：x天前
 * - 超过 1 周、今年内：MM/DD
 * - 不是今年：YYYY/MM/DD
 */
export function formatFeedTime(ts: number): string {
  const MS = 1;
  const MINUTE = MS * 1000 * 60;
  const HOUR = MINUTE * 60;
  const DAY = HOUR * 24;
  const WEEK = DAY * 7;

  const normalizedTs = normalizeTimestamp(ts);
  const now = Date.now();
  const diff = now - normalizedTs;

  if (diff <= 0) return '刚刚';
  if (diff < MINUTE) return '刚刚';
  if (diff < HOUR) {
    const m = Math.floor(diff / MINUTE);
    return `${m}分钟前`;
  }
  if (diff < DAY) {
    const h = Math.floor(diff / HOUR);
    return `${h}小时前`;
  }
  if (diff < WEEK) {
    const d = Math.floor(diff / DAY);
    return `${d}天前`;
  }

  const target = new Date(normalizedTs);
  const today = new Date(now);
  const pad = (n: number) => String(n).padStart(2, '0');
  const MM = pad(target.getMonth() + 1);
  const DD = pad(target.getDate());

  if (target.getFullYear() !== today.getFullYear()) {
    return `${target.getFullYear()}/${MM}/${DD}`;
  }
  return `${MM}/${DD}`;
}