export function getNumberOfWeeks(year){
  const firstDayOfYear = new Date(year, 0, 1);
  const lastDayOfYear = new Date(year, 11, 31);
  const daysInYear = (lastDayOfYear - firstDayOfYear) / (24 * 60 * 60 * 1000) + 1;
  const weeksInYear = Math.ceil(daysInYear / 7);
  return weeksInYear;
}
export function currentWeek(){
	let now = new Date();
	let currentYear = now.getFullYear();
	let firstDayOfYear = new Date(currentYear, 0, 1);
	let diffDays = Math.floor((now - firstDayOfYear) / (24 * 60 * 60 * 1000));
	let currentWeek = Math.ceil((diffDays + firstDayOfYear.getDay() + 1) / 7);
	return currentWeek 
}
export function getDateByWeek(week, year) {
  year = year || new Date().getFullYear();
  let currentDate = new Date(year, 0, 1); // 当年的1月1日
  let numDays = currentDate.getDay(); // 获取当年第一天是周几
  if (numDays === 0) numDays = 7; // 如果是周日，则numDays设为7
  let firstThursday = new Date(currentDate.getTime() + (4 - numDays) * 86400000); // 当年第一个周四
  let firstWeek = Math.ceil((firstThursday.getDate() - 1) / 7); // 第一个周四前的周数
 
  week = week + firstWeek; // 加上第一个周四的周数
  if (week === 0) {
    year -= 1; // 如果是0周，则获取上一年的最后一周
    week = getWeekNumber(new Date(year, 11, 31)); // 上一年12月31日的周数
  } else if (week > 52 && getWeekNumber(new Date(year + 1, 0, 3)) === 1) {
    year += 1; // 如果超过52周且下一年的1月3日是周一，则获取下一年的第一周
    week = 1;
  }
 
  currentDate = new Date(year, 0, 1); // 设置为当年的1月1日
  currentDate.setDate(currentDate.getDate() + (week - 1) * 7); // 计算当周的日期
  return currentDate; // 返回当前周的日期
}
 
function getWeekNumber(date) {
  let currentDate = new Date(date.getTime());
  let numDays = currentDate.getDay();
  if (numDays === 0) numDays = 7;
  currentDate.setDate(currentDate.getDate() + 3 - numDays); // 周一
  let firstDayYear = new Date(currentDate.getFullYear(), 0, 1); // 当年的1月1日
  let firstWeek = Math.ceil((firstDayYear.getDay() - firstDayYear.getDay() % 7) / 7); // 第一个周一是当年的第几周
  let weekNumber = Math.ceil((currentDate.getDay() * 5 - firstDayYear.getDay() + 10) / 7); // 当前周数
  return firstWeek + weekNumber;
}
export function parseTime(time, cFormat) {
  if (arguments.length === 0 || !time) {
    return null
  }
  const format = cFormat || '{y}-{m}-{d} {h}:{i}:{s}'
  let date
  if (typeof time === 'object') {
    date = time
  } else {
    if ((typeof time === 'string')) {
      if ((/^[0-9]+$/.test(time))) {
        // support "1548221490638"
        time = parseInt(time)
      } else {
        // support safari
        // https://stackoverflow.com/questions/4310953/invalid-date-in-safari
        time = time.replace(new RegExp(/-/gm), '/')
      }
    }

    if ((typeof time === 'number') && (time.toString().length === 10)) {
      time = time * 1000
    }
    date = new Date(time)
  }
  const formatObj = {
    y: date.getFullYear(),
    m: date.getMonth() + 1,
    d: date.getDate(),
    h: date.getHours(),
    i: date.getMinutes(),
    s: date.getSeconds(),
    a: date.getDay()
  }
  const time_str = format.replace(/{([ymdhisa])+}/g, (result, key) => {
    const value = formatObj[key]
    // Note: getDay() returns 0 on Sunday
    if (key === 'a') { return ['日', '一', '二', '三', '四', '五', '六'][value ] }
    return value.toString().padStart(2, '0')
  })
  return time_str
}