/**
 * 农历转换工具
 * 支持 1900-2100 年的公历农历互转
 */

// 农历数据表 (1900-2100)
// 每个数字的后12位代表12个月，1为大月(30天)，0为小月(29天)
// 前4位代表闰月月份，0表示无闰月
const lunarInfo = [
  0x04bd8, 0x04ae0, 0x0a570, 0x054d5, 0x0d260, 0x0d950, 0x16554, 0x056a0, 0x09ad0, 0x055d2,
  0x04ae0, 0x0a5b6, 0x0a4d0, 0x0d250, 0x1d255, 0x0b540, 0x0d6a0, 0x0ada2, 0x095b0, 0x14977,
  0x04970, 0x0a4b0, 0x0b4b5, 0x06a50, 0x06d40, 0x1ab54, 0x02b60, 0x09570, 0x052f2, 0x04970,
  0x06566, 0x0d4a0, 0x0ea50, 0x06e95, 0x05ad0, 0x02b60, 0x186e3, 0x092e0, 0x1c8d7, 0x0c950,
  0x0d4a0, 0x1d8a6, 0x0b550, 0x056a0, 0x1a5b4, 0x025d0, 0x092d0, 0x0d2b2, 0x0a950, 0x0b557,
  0x06ca0, 0x0b550, 0x15355, 0x04da0, 0x0a5b0, 0x14573, 0x052b0, 0x0a9a8, 0x0e950, 0x06aa0,
  0x0aea6, 0x0ab50, 0x04b60, 0x0aae4, 0x0a570, 0x05260, 0x0f263, 0x0d950, 0x05b57, 0x056a0,
  0x096d0, 0x04dd5, 0x04ad0, 0x0a4d0, 0x0d4d4, 0x0d250, 0x0d558, 0x0b540, 0x0b6a0, 0x195a6,
  0x095b0, 0x049b0, 0x0a974, 0x0a4b0, 0x0b27a, 0x06a50, 0x06d40, 0x0af46, 0x0ab60, 0x09570,
  0x04af5, 0x04970, 0x064b0, 0x074a3, 0x0ea50, 0x06b58, 0x055c0, 0x0ab60, 0x096d5, 0x092e0,
  0x0c960, 0x0d954, 0x0d4a0, 0x0da50, 0x07552, 0x056a0, 0x0abb7, 0x025d0, 0x092d0, 0x0cab5,
  0x0a950, 0x0b4a0, 0x0baa4, 0x0ad50, 0x055d9, 0x04ba0, 0x0a5b0, 0x15176, 0x052b0, 0x0a930,
  0x07954, 0x06aa0, 0x0ad50, 0x05b52, 0x04b60, 0x0a6e6, 0x0a4e0, 0x0d260, 0x0ea65, 0x0d530,
  0x05aa0, 0x076a3, 0x096d0, 0x04afb, 0x04ad0, 0x0a4d0, 0x1d0b6, 0x0d250, 0x0d520, 0x0dd45,
  0x0b5a0, 0x056d0, 0x055b2, 0x049b0, 0x0a577, 0x0a4b0, 0x0aa50, 0x1b255, 0x06d20, 0x0ada0,
  0x14b63, 0x09370, 0x049f8, 0x04970, 0x064b0, 0x168a6, 0x0ea50, 0x06b20, 0x1a6c4, 0x0aae0,
  0x0a2e0, 0x0d2e3, 0x0c960, 0x0d557, 0x0d4a0, 0x0da50, 0x05d55, 0x056a0, 0x0a6d0, 0x055d4,
  0x052d0, 0x0a9b8, 0x0a950, 0x0b4a0, 0x0b6a6, 0x0ad50, 0x055a0, 0x0aba4, 0x0a5b0, 0x052b0,
  0x0b273, 0x06930, 0x07337, 0x06aa0, 0x0ad50, 0x14b55, 0x04b60, 0x0a570, 0x054e4, 0x0d160,
  0x0e968, 0x0d520, 0x0daa0, 0x16aa6, 0x056d0, 0x04ae0, 0x0a9d4, 0x0a2d0, 0x0d150, 0x0f252,
  0x0d520,
]

// 天干
const Gan = ['甲', '乙', '丙', '丁', '戊', '己', '庚', '辛', '壬', '癸']
// 地支
const Zhi = ['子', '丑', '寅', '卯', '辰', '巳', '午', '未', '申', '酉', '戌', '亥']
// 生肖
const Animals = ['鼠', '牛', '虎', '兔', '龙', '蛇', '马', '羊', '猴', '鸡', '狗', '猪']
// 农历月份
const lunarMonths = ['正', '二', '三', '四', '五', '六', '七', '八', '九', '十', '冬', '腊']
// 农历日期
const lunarDays = [
  '初一', '初二', '初三', '初四', '初五', '初六', '初七', '初八', '初九', '初十',
  '十一', '十二', '十三', '十四', '十五', '十六', '十七', '十八', '十九', '二十',
  '廿一', '廿二', '廿三', '廿四', '廿五', '廿六', '廿七', '廿八', '廿九', '三十',
]

/**
 * 获取农历年份的闰月月份
 * @param year 农历年份
 * @returns 闰月月份，0表示无闰月
 */
function leapMonth(year: number): number {
  return lunarInfo[year - 1900] & 0xf
}

/**
 * 获取农历年份的闰月天数
 * @param year 农历年份
 * @returns 闰月天数
 */
function leapDays(year: number): number {
  if (leapMonth(year)) {
    return lunarInfo[year - 1900] & 0x10000 ? 30 : 29
  }
  return 0
}

/**
 * 获取农历年份的总天数
 * @param year 农历年份
 * @returns 总天数
 */
function yearDays(year: number): number {
  let sum = 348
  for (let i = 0x8000; i > 0x8; i >>= 1) {
    sum += lunarInfo[year - 1900] & i ? 1 : 0
  }
  return sum + leapDays(year)
}

/**
 * 获取农历年份某月的天数
 * @param year 农历年份
 * @param month 农历月份
 * @returns 该月天数
 */
function monthDays(year: number, month: number): number {
  return lunarInfo[year - 1900] & (0x10000 >> month) ? 30 : 29
}

/**
 * 公历转农历
 * @param date 公历日期
 * @returns 农历信息,如果日期超出范围则返回null
 */
export function solar2lunar(date: Date) {
  const inputYear = date.getFullYear()
  
  // 检查年份范围
  if (inputYear < 1900 || inputYear > 2100) {
    return null
  }
  
  const baseDate = new Date(1900, 0, 31)
  let offset = Math.floor((date.getTime() - baseDate.getTime()) / 86400000)

  let year = 1900
  let daysInYear = 0

  // 计算农历年份
  while (year < 2101 && offset > 0) {
    daysInYear = yearDays(year)
    offset -= daysInYear
    year++
  }

  if (offset < 0) {
    offset += daysInYear
    year--
  }

  // 农历年份
  const lunarYear = year
  const leap = leapMonth(year)
  let isLeap = false

  // 计算农历月份
  let month = 1
  let daysOfMonth = 0
  for (month = 1; month <= 12 && offset > 0; month++) {
    // 闰月
    if (leap > 0 && month === leap + 1 && !isLeap) {
      --month
      isLeap = true
      daysOfMonth = leapDays(year)
    } else {
      daysOfMonth = monthDays(year, month)
    }

    // 解除闰月
    if (isLeap && month === leap + 1) {
      isLeap = false
    }

    offset -= daysOfMonth
  }

  // 修正月份
  if (offset === 0 && leap > 0 && month === leap + 1) {
    if (isLeap) {
      isLeap = false
    } else {
      isLeap = true
      --month
    }
  }

  if (offset < 0) {
    offset += daysOfMonth
    --month
  }

  const lunarMonth = month
  const lunarDay = offset + 1

  // 计算干支年
  const ganIndex = (lunarYear - 4) % 10
  const zhiIndex = (lunarYear - 4) % 12
  const ganZhiYear = Gan[ganIndex] + Zhi[zhiIndex]

  // 生肖
  const animal = Animals[(lunarYear - 4) % 12]

  // 确保月份和日期在有效范围内
  const validMonth = Math.max(1, Math.min(12, lunarMonth))
  const validDay = Math.max(1, Math.min(30, lunarDay))

  return {
    lunarYear,
    lunarMonth: validMonth,
    lunarDay: validDay,
    isLeap,
    ganZhiYear,
    animal,
    monthName: (isLeap ? '闰' : '') + (lunarMonths[validMonth - 1] || '未知') + '月',
    dayName: lunarDays[validDay - 1] || '未知',
    toString: function () {
      return `${this.ganZhiYear}年(${this.animal})${this.monthName}${this.dayName}`
    },
  }
}

/**
 * 农历转公历
 * @param year 农历年份
 * @param month 农历月份
 * @param day 农历日期
 * @param isLeap 是否闰月
 * @returns 公历日期
 */
export function lunar2solar(year: number, month: number, day: number, isLeap = false): Date | null {
  if (year < 1900 || year > 2100) {
    return null
  }

  const leap = leapMonth(year)
  if (isLeap && leap !== month) {
    return null
  }

  // 计算从1900年1月31日到目标日期的天数
  let offset = 0

  // 累加年份天数
  for (let i = 1900; i < year; i++) {
    offset += yearDays(i)
  }

  // 累加月份天数
  let leapFlag = false
  for (let i = 1; i < month; i++) {
    offset += monthDays(year, i)
  }

  // 如果是闰月，需要加上闰月之前的月份
  if (leap > 0 && month > leap) {
    offset += leapDays(year)
    if (month === leap + 1 && isLeap) {
      leapFlag = true
    }
  }

  // 加上日期
  offset += day - 1

  const baseDate = new Date(1900, 0, 31)
  const resultDate = new Date(baseDate.getTime() + offset * 86400000)

  return resultDate
}

/**
 * 格式化日期为 YYYY-MM-DD
 */
export function formatDate(date: Date): string {
  const year = date.getFullYear()
  const month = String(date.getMonth() + 1).padStart(2, '0')
  const day = String(date.getDate()).padStart(2, '0')
  return `${year}-${month}-${day}`
}

/**
 * 解析 YYYY-MM-DD 格式的日期字符串
 */
export function parseDate(dateStr: string): Date | null {
  if (!dateStr) return null
  const parts = dateStr.split('-')
  if (parts.length !== 3) return null
  const year = parseInt(parts[0])
  const month = parseInt(parts[1]) - 1
  const day = parseInt(parts[2])
  return new Date(year, month, day)
}

/**
 * 检查某个日期是否在当前月份
 * @param dateStr 日期字符串 YYYY-MM-DD
 * @param isLunar 是否按农历计算
 * @returns 如果在当前月份返回日期信息,否则返回null
 */
export function isInCurrentMonth(dateStr: string, isLunar: boolean = false): { day: number; month: number } | null {
  const date = parseDate(dateStr)
  if (!date) return null

  const now = new Date()
  const currentYear = now.getFullYear()
  const currentMonth = now.getMonth() + 1

  if (isLunar) {
    // 按农历计算:获取原日期的农历信息
    const originalLunar = solar2lunar(date)
    if (!originalLunar) return null

    // 计算今年对应的农历日期的公历日期
    const thisYearSolar = lunar2solar(
      currentYear,
      originalLunar.lunarMonth,
      originalLunar.lunarDay,
      originalLunar.isLeap
    )

    if (!thisYearSolar) {
      // 如果转换失败，尝试用明年的日期
      const nextYearSolar = lunar2solar(
        currentYear + 1,
        originalLunar.lunarMonth,
        originalLunar.lunarDay,
        originalLunar.isLeap
      )
      if (nextYearSolar) {
        const nextYearMonth = nextYearSolar.getMonth() + 1
        const nextYearDay = nextYearSolar.getDate()
        if (nextYearMonth === currentMonth) {
          return { day: nextYearDay, month: nextYearMonth }
        }
      }
      return null
    }

    const thisYearMonth = thisYearSolar.getMonth() + 1
    const thisYearDay = thisYearSolar.getDate()

    if (thisYearMonth === currentMonth) {
      return { day: thisYearDay, month: thisYearMonth }
    }
  } else {
    // 按公历计算:直接比较月份
    const month = date.getMonth() + 1
    const day = date.getDate()

    if (month === currentMonth) {
      return { day, month }
    }
  }

  return null
}