class DateUtil {
  static formatDateToMonthDay(dateStr) {
    const date = DateUtil._parseDate(dateStr);
    if (!DateUtil._isValidDate(date)) return '';
    return `${date.getMonth() + 1}月${date.getDate()}日`;
  }

  static formatDateToYearMonthDay(dateStr) {
    const date = DateUtil._parseDate(dateStr);
    if (!DateUtil._isValidDate(date)) return '';
    return `${date.getFullYear()}年${date.getMonth() + 1}月${date.getDate()}日`;
  }

  static formatDateToYMD(dateStr) {
    const date = DateUtil._parseDate(dateStr);
    if (!DateUtil._isValidDate(date)) return '';
    return [
      date.getFullYear(),
      String(date.getMonth() + 1).padStart(2, '0'),
      String(date.getDate()).padStart(2, '0'),
    ].join('-');
  }

  static formatDateTimeToYMDHMS(dateStr) {
    const date = DateUtil._parseDate(dateStr);
    if (!DateUtil._isValidDate(date)) return '';
    return `${DateUtil.formatDateToYMD(date)} ${DateUtil._timeParts(date).join(':')}`;
  }

  static formatDateTimeToYMDHM(dateStr) {
    const date = DateUtil._parseDate(dateStr);
    if (!DateUtil._isValidDate(date)) return '';
    const [hour, minute] = DateUtil._timeParts(date);
    return `${DateUtil.formatDateToYMD(date)} ${hour}:${minute}`;
  }

  static formatTimeToHMS(dateStr) {
    const date = typeof dateStr === 'number' ? new Date(dateStr) : DateUtil._parseDate(dateStr);
    if (!DateUtil._isValidDate(date)) return '';
    return DateUtil._timeParts(date).join(':');
  }

  static getCurrentDate() {
    return new Date();
  }

  static isSameDay(date1, date2) {
    const d1 = DateUtil._parseDate(date1);
    const d2 = DateUtil._parseDate(date2);
    if (!DateUtil._isValidDate(d1) || !DateUtil._isValidDate(d2)) return false;
    return (
      d1.getFullYear() === d2.getFullYear() &&
      d1.getMonth() === d2.getMonth() &&
      d1.getDate() === d2.getDate()
    );
  }

  static _parseDate(dateStr) {
    if (dateStr instanceof Date) return dateStr;
    if (typeof dateStr === 'number') return new Date(dateStr);
    if (typeof dateStr !== 'string') return null;
    const value = dateStr.trim();
    if (!value) return null;
    if (/^\d{4}-\d{2}-\d{2}$/.test(value)) {
      return new Date(value.replace(/-/g, '/'));
    }
    return new Date(value);
  }

  static _isValidDate(date) {
    return date instanceof Date && !Number.isNaN(date.getTime());
  }

  static _timeParts(date) {
    return [
      String(date.getHours()).padStart(2, '0'),
      String(date.getMinutes()).padStart(2, '0'),
      String(date.getSeconds()).padStart(2, '0'),
    ];
  }
}

if (typeof module !== 'undefined' && module.exports) {
  module.exports = DateUtil;
} else if (typeof window !== 'undefined') {
  window.DateUtil = DateUtil;
}