const weekDayNumber = 7
const week_zh_cn = ['周日', '周一', '周二', '周三', '周四', '周五', '周六']
const week_en_us = ['SUN', 'MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT']

class Day {
  constructor(year, month, day, content, isCurrentMonth = false, isCurrentDay = false) {
    this.year = year
    this.month = month
    this.day = day
    this.content = content
    this.isCurrentMonth = isCurrentMonth
    this.isCurrentDay = isCurrentDay
  }
}

const defaultDate = new Date()
const defaultYear = defaultDate.getFullYear()
const defaultMonth = defaultDate.getMonth()
const defaultDay = defaultDate.getDate()

/**
 * 初始化日历
 * @param {[Day]} currentDays
 * @param {number} [year = defaultYear]
 * @param {number} [month = defaultMonth]
 * @param {number} [day = defaultDay]
 * @returns {[Day]}
 */
function initDay(
  currentDays = new Array(42),
  year = defaultYear,
  month = defaultMonth,
  day = defaultDay
) {
  if (!Array.isArray(currentDays)) {
    currentDays = new Array(42)
  } else if (currentDays.length !== 42) {
    console.log(currentDays)
    throw new Error('currentDays:' + currentDays)
  } else {
    currentDays = [...currentDays]
  }

  const days = currentDays
  const lastDayOfLastMonth = new Date(year, month, 0)
  const firstDayOfMonth = new Date(year, month, 1)
  const lastDayOfMonth = new Date(year, month + 1, 0)
  const currentDaysOfMonth = lastDayOfMonth.getDate()
  const daysOfLastMonth = lastDayOfLastMonth.getDate()

  for (let i = 0; i < firstDayOfMonth.getDay(); i++) {
    const weekDay = firstDayOfMonth.getDay() - 1
    days[i] = new Day(year, month - 1, daysOfLastMonth - weekDay + i, week_zh_cn[i])
  }

  for (let i = 0; i < currentDaysOfMonth; i++) {
    const weekDay = (firstDayOfMonth.getDay() + i) % weekDayNumber
    days[firstDayOfMonth.getDay() + i] = new Day(year, month, i + 1, week_zh_cn[weekDay], true)
    if (i === day - 1) {
      days[firstDayOfMonth.getDay() + i].isCurrentDay = true
    }
  }

  for (let i = currentDaysOfMonth + firstDayOfMonth.getDay(); i < days.length; i++) {
    const extraDay = i - currentDaysOfMonth - firstDayOfMonth.getDay() + 1
    const weekDay = i % weekDayNumber
    days[i] = new Day(year, month + 1, extraDay, week_zh_cn[weekDay])
  }

  return currentDays
}

export { week_zh_cn, week_en_us, defaultYear, defaultMonth, defaultDay, initDay }