import { Lunar, Solar } from "lunar-javascript";

export interface LunarDateParts {
  year: number;
  month: number;
  day: number;
  isLeapMonth: boolean;
}

/** 农历 → 阳历 YYYY-MM-DD，无效则 null */
export function lunarToSolarYmd(parts: LunarDateParts): string | null {
  try {
    const month = parts.isLeapMonth ? -parts.month : parts.month;
    const lunar = Lunar.fromYmd(parts.year, month, parts.day);
    return lunar.getSolar().toYmd();
  } catch {
    return null;
  }
}

/** 阳历 YYYY-MM-DD → 农历分量 */
export function solarYmdToLunarParts(ymd: string): LunarDateParts | null {
  try {
    const [y, m, d] = ymd.split("-").map(Number);
    if (!y || !m || !d) {
      return null;
    }
    const lunar = Solar.fromYmd(y, m, d).getLunar();
    const month = lunar.getMonth();
    return {
      year: lunar.getYear(),
      month: Math.abs(month),
      day: lunar.getDay(),
      isLeapMonth: month < 0,
    };
  } catch {
    return null;
  }
}

/** 格式化农历显示 */
export function formatLunarLabel(parts: LunarDateParts): string | null {
  try {
    const month = parts.isLeapMonth ? -parts.month : parts.month;
    return Lunar.fromYmd(parts.year, month, parts.day).toString();
  } catch {
    return null;
  }
}

/** 格式化阳历显示 */
export function formatSolarLabel(ymd: string): string | null {
  try {
    const [y, m, d] = ymd.split("-").map(Number);
    if (!y || !m || !d) {
      return null;
    }
    const solar = Solar.fromYmd(y, m, d);
    const week = ["日", "一", "二", "三", "四", "五", "六"][solar.getWeek()];
    return `${y}年${m}月${d}日 星期${week}`;
  } catch {
    return null;
  }
}

export function todayLunarParts(): LunarDateParts {
  const lunar = Solar.fromDate(new Date()).getLunar();
  const month = lunar.getMonth();
  return {
    year: lunar.getYear(),
    month: Math.abs(month),
    day: lunar.getDay(),
    isLeapMonth: month < 0,
  };
}

export function todaySolarYmd(): string {
  return Solar.fromDate(new Date()).toYmd();
}