import { defaultFormatPattern, patternRegExp, weeks } from './constants';
import { createDateInstance, paddingLeftZero } from './utils';
import { LikeDate } from './model';

/**
 *
 * @param date 将要格式化的日期
 * @param pattern 格式化模式，默认为：'yyyy年MM月dd日 hh时mm分ss秒'
 * @example
 * 格式化当前日期 format()
 * 传入时间戳 format(1607000082114)
 */
function format(
  date?: LikeDate,
  pattern: string = defaultFormatPattern,
): string {
  const dateInstance = createDateInstance(date);
  if (!dateInstance) {
    return '';
  }

  if (typeof pattern !== 'string') {
    pattern = defaultFormatPattern;
  }

  return pattern.replace(patternRegExp, (match, $1): string => {
    const { length } = $1;
    const year = dateInstance.getFullYear().toString();
    switch ($1.charAt(0)) {
      case 'y':
        return year.substr(year.length - length);
      case 'M':
        return paddingLeftZero(dateInstance.getMonth() + 1, length);
      case 'd':
        return paddingLeftZero(dateInstance.getDate(), length);
      case 'w':
        return String(dateInstance.getDay() === 0 ? 7 : dateInstance.getDay());
      case 'W':
        return weeks[dateInstance.getDay()];
      case 'h':
        return paddingLeftZero(dateInstance.getHours(), length);
      case 'm':
        return paddingLeftZero(dateInstance.getMinutes(), length);
      case 's':
        return paddingLeftZero(dateInstance.getSeconds(), length);
      default:
        return '';
    }
  });
}

/**
 * 比较两个日期
 * date1 = date2 return 0
 * date1 > date2 return 1
 * date1 < date2 return -1
 * @param {*} date1 日期一
 * @param {*} date2 日期二
 */
function compare(date1: LikeDate, date2: LikeDate): number {
  const firstTimestamp = createDateInstance(date1)?.getTime();
  const secondTimestamp = createDateInstance(date2)?.getTime();

  if (!firstTimestamp || !secondTimestamp) return Number.NaN;

  if (firstTimestamp - secondTimestamp === 0) {
    return 0;
  }

  return firstTimestamp - secondTimestamp > 0 ? 1 : -1;
}

/**
 * 计算2日期之间的天数
 * @param date1 日期一
 * @param date2 日期二
 */
function countDays(date1: LikeDate, date2: LikeDate): number {
  const firstTimestamp = createDateInstance(date1)?.getTime();
  const secondTimestamp = createDateInstance(date2)?.getTime();

  if (!firstTimestamp || !secondTimestamp) return Number.NaN;

  return Math.abs(firstTimestamp - secondTimestamp) / (24 * 60 * 60 * 1000);
}

/**
 * 是否是闰年
 * @param {*} year 年份
 */
function isLeapYear(year: number): boolean {
  return (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0;
}
/**
 * 获取某月的天数
 * @param {*} month 月份，从1开始，取值为1~12
 * @param {*} year 年份，可选，用于判断是否为闰年，默认为当前年
 */
function getDaysOfMonth(
  month: number,
  year = new Date().getFullYear(),
): number {
  const days = [
    31,
    isLeapYear(year) ? 29 : 28,
    31,
    30,
    31,
    30,
    31,
    31,
    30,
    31,
    30,
    31,
  ];
  return days[month - 1];
}

/**
 * 获取昨天日期
 * @param {*} pattern 格式化模式，可选，形式同format函数第二个参数，不传则返回日期对象
 */
function getYesterday(pattern?: string): string | Date {
  const date = new Date();
  date.setDate(date.getDate() - 1);

  if (pattern) {
    return format(date, pattern);
  }

  return date;
}

/**
 * 获取明天日期
 * @param {*} pattern 格式化模式，可选，形式同format函数第二个参数，不传则返回日期对象
 */
function getTomorrow(pattern?: string): string | Date {
  const date = new Date();
  date.setDate(date.getDate() + 1);

  if (pattern) {
    return format(date, pattern);
  }

  return date;
}

/**
 * 根据生日获取年龄
 * @param birthday 生日
 * @param strict 是否严格计算，默认为true
 * @returns age 年龄
 * @description 传入生日无法转换成日期时，会返回 -1
 * @description 禁止严格计算时，只计算年份的差值；开启严格计算时，会根据年月日严格计算
 */
function getAgeByBirthday(birthday: LikeDate, strict = true): number {
  const birthDate = createDateInstance(birthday);
  const nowDate = new Date();

  if (!birthDate) return -1;

  const yearDiff = nowDate.getFullYear() - birthDate.getFullYear();
  const monthDiff = nowDate.getMonth() - birthDate.getMonth();
  const dayDiff = nowDate.getDate() - birthDate.getDate();

  if (!strict) return yearDiff;

  const age =
    monthDiff < 0 || (monthDiff === 0 && dayDiff < 0) ? yearDiff - 1 : yearDiff;
  return age < 0 ? 0 : age;
}

function isValid(date: LikeDate) {
  return createDateInstance(date) !== null;
}

export {
  format,
  compare,
  countDays,
  isLeapYear,
  getDaysOfMonth,
  getYesterday,
  getTomorrow,
  getAgeByBirthday,
  isValid,
};