/**
 * System Date Skill
 * 获取当前日期和时间（北京时间 UTC+8）
 */

/**
 * 获取北京时间
 */
function getBeijingTime() {
  const now = new Date();
  // UTC 时间 + 8 小时 = 北京时间
  const beijingTime = new Date(now.getTime() + (8 * 60 * 60 * 1000));
  return beijingTime;
}

/**
 * 计算农历日期（2026 年春节 2 月 17 日 = 正月初一）
 */
function getLunarDate(beijingDate) {
  const springFestival = new Date('2026-02-17T00:00:00'); // 春节北京时间
  const diffMs = beijingDate.getTime() - springFestival.getTime();
  const daysSince = Math.floor(diffMs / (1000 * 60 * 60 * 24));
  const lunarDay = daysSince + 1; // 正月初一是第 1 天
  
  if (lunarDay >= 1 && lunarDay <= 30) {
    return `农历正月初${lunarDay}`;
  } else {
    return `农历${lunarDay > 30 ? '二月' : '腊月'}${Math.abs(lunarDay - 30)}`;
  }
}

/**
 * 获取当前日期时间（北京时间）
 */
function getCurrentDateTime() {
  const beijingNow = getBeijingTime();
  
  const year = beijingNow.getFullYear();
  const month = beijingNow.getMonth() + 1;
  const day = beijingNow.getDate();
  const weekdays = ['日', '一', '二', '三', '四', '五', '六'];
  const weekday = `星期${weekdays[beijingNow.getDay()]}`;
  
  return {
    success: true,
    timezone: 'Asia/Shanghai',
    year: year,
    month: month,
    day: day,
    weekday: weekday,
    fullDate: `${year}年${month}月${day}日`,
    lunarDate: getLunarDate(beijingNow),
    isoString: beijingNow.toISOString()
  };
}

/**
 * 获取相对日期（北京时间）
 */
function getRelativeDate(relative = 'today') {
  const beijingNow = getBeijingTime();
  let targetDate = new Date(beijingNow);
  
  switch (relative.toLowerCase()) {
    case 'today':
    case '今天':
      break;
    case 'tomorrow':
    case '明天':
      targetDate.setDate(targetDate.getDate() + 1);
      break;
    case 'yesterday':
    case '昨天':
      targetDate.setDate(targetDate.getDate() - 1);
      break;
  }
  
  const year = targetDate.getFullYear();
  const month = targetDate.getMonth() + 1;
  const day = targetDate.getDate();
  const weekdays = ['日', '一', '二', '三', '四', '五', '六'];
  const weekday = `星期${weekdays[targetDate.getDay()]}`;
  
  return {
    success: true,
    relative: relative,
    year: year,
    month: month,
    day: day,
    weekday: weekday,
    fullDate: `${year}年${month}月${day}日`,
    lunarDate: getLunarDate(targetDate),
    timezone: 'Asia/Shanghai'
  };
}

/**
 * 格式化日期为可读文本
 */
function formatDateInfo(dateInfo, includeLunar = true) {
  const lines = [
    `📅 **${dateInfo.fullDate}**`,
    `**星期:** ${dateInfo.weekday}`,
  ];
  
  if (includeLunar && dateInfo.lunarDate) {
    lines.push(`**农历:** ${dateInfo.lunarDate}`);
  }
  
  lines.push(`**时区:** ${dateInfo.timezone || 'Asia/Shanghai'}`);
  
  return lines.join('\n');
}

// 命令行测试
if (require.main === module) {
  console.log('=== 北京时间测试 ===');
  console.log('今天:', new Date(new Date().getTime() + 8*60*60*1000).toISOString());
  console.log('');
  
  const arg = process.argv[2] || 'today';
  const result = getRelativeDate(arg);
  console.log(formatDateInfo(result));
}

module.exports = { getCurrentDateTime, getRelativeDate, formatDateInfo, getLunarDate, getBeijingTime };