import { dayjs, dayjsLocal } from '../../utils/dayjs'
import type { Dayjs } from 'dayjs'
import type { DatePickerDateObj as DateObj } from './types'

// Constant list of month labels
export const months: string[] = [
  'Jan',
  'Feb',
  'Mar',
  'Apr',
  'May',
  'Jun',
  'Jul',
  'Aug',
  'Sep',
  'Oct',
  'Nov',
  'Dec',
]

// Start of given month (0-indexed month)
export function monthStart(year: number, monthIndex: number): Dayjs {
  return dayjs(`${year}-${monthIndex + 1}-01`)
}

// Build weeks grid for the calendar
export function generateWeeks(
  year: number,
  monthIndex: number,
  selected: string,
): DateObj[][] {
  const start = monthStart(year, monthIndex).startOf('week')
  const end = monthStart(year, monthIndex).endOf('month').endOf('week')
  const days: DateObj[] = []
  let d: Dayjs = start
  while (d.isBefore(end) || d.isSame(end)) {
    const inMonth = d.month() === monthIndex
    const sel = dayjs(selected)
    days.push({
      date: d,
      key: d.format('YYYY-MM-DD'),
      inMonth,
      isToday: d.isSame(dayjsLocal().format('YYYY-MM-DD'), 'day'),
      isSelected: sel.isValid() && d.isSame(sel, 'day'),
    })
    d = d.add(1, 'day')
  }
  const chunked: DateObj[][] = []
  for (let i = 0; i < days.length; i += 7) chunked.push(days.slice(i, i + 7))
  return chunked
}

type DateConstructorParam = string | number | Date

function getDate(...args: DateConstructorParam[]): Date {
  return new Date(...(args as [DateConstructorParam]))
}

function getDateValue(date: Date | string) {
  if (!date || date.toString() === 'Invalid Date') return ''

  return dayjs(date)
    .set('hour', 0)
    .set('minute', 0)
    .set('second', 0)
    .set('millisecond', 0)
    .format('YYYY-MM-DD')
}

function getDatesAfter(date: Date, count: number) {
  let incrementer = 1
  if (count < 0) {
    incrementer = -1
    count = Math.abs(count)
  }
  const dates: Date[] = []

  while (count) {
    date = getDate(
      date.getFullYear(),
      date.getMonth(),
      date.getDate() + incrementer,
    )
    dates.push(date)
    count--
  }

  if (incrementer === -1) {
    return dates.reverse()
  }
  return dates
}

function getDaysInMonth(monthIndex: number, year: number) {
  const daysInMonthMap = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
  const daysInMonth = daysInMonthMap[monthIndex]
  if (monthIndex === 1 && isLeapYear(year)) {
    return 29
  }
  return daysInMonth
}

function isLeapYear(year: number) {
  if (year % 400 === 0) return true
  if (year % 100 === 0) return false
  if (year % 4 === 0) return true
  return false
}

export { getDate, getDateValue, getDatesAfter, getDaysInMonth, isLeapYear }