import fecha from 'element-ui/src/utils/date'
import { t } from 'element-ui/src/locale'

const weeks = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat']
const months = ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec']

const newArray = function(start, end) {
 let result = []
 for (let i = start; i <= end; i++) {
 result.push(i)
 }
 return result
}

export const getI18nSettings = () => {
 return {
 dayNamesShort: weeks.map(week => t(`el.datepicker.weeks.${ week }`)),
 dayNames: weeks.map(week => t(`el.datepicker.weeks.${ week }`)),
 monthNamesShort: months.map(month => t(`el.datepicker.months.${ month }`)),
 monthNames: months.map((month, index) => t(`el.datepicker.month${ index + 1 }`)),
 amPm: ['am', 'pm']
 }
}

export const toDate = function(date) {
 return isDate(date) ? new Date(date) : null
}

export const isDate = function(date) {
 if (date === null || date === undefined) return false
 if (isNaN(new Date(date).getTime())) return false
 if (Array.isArray(date)) return false // deal with `new Date([ new Date() ]) -> new Date()`
 return true
}

export const isDateObject = function(val) {
 return val instanceof Date
}

export const formatDate = function(date, format) {
 date = toDate(date)
 if (!date) return ''
 return fecha.format(date, format || 'yyyy-MM-dd', getI18nSettings())
}

export const parseDate = function(string, format) {
 return fecha.parse(string, format || 'yyyy-MM-dd', getI18nSettings())
}

export const getDayCountOfMonth = function(year, month) {
 if (month === 3 || month === 5 || month === 8 || month === 10) {
 return 30
 }

 if (month === 1) {
 if (year % 4 === 0 && year % 100 !== 0 || year % 400 === 0) {
 return 29
 } else {
 return 28
 }
 }

 return 31
}

export const getDayCountOfYear = function(year) {
 const isLeapYear = year % 400 === 0 || (year % 100 !== 0 && year % 4 === 0)
 return isLeapYear ? 366 : 365
}

export const getFirstDayOfMonth = function(date) {
 const temp = new Date(date.getTime())
 temp.setDate(1)
 return temp.getDay()
}

// see: https://stackoverflow.com/questions/3674539/incrementing-a-date-in-javascript
// {prev, next} Date should work for Daylight Saving Time
// Adding 24 * 60 * 60 * 1000 does not work in the above scenario
export const prevDate = function(date, amount = 1) {
 return new Date(date.getFullYear(), date.getMonth(), date.getDate() - amount)
}

export const nextDate = function(date, amount = 1) {
 return new Date(date.getFullYear(), date.getMonth(), date.getDate() + amount)
}

export const getStartDateOfMonth = function(year, month) {
 const result = new Date(year, month, 1)
 const day = result.getDay()

 if (day === 0) {
 return prevDate(result, 7)
 } else {
 return prevDate(result, day)
 }
}

export const getWeekNumber = function(src) {
 if (!isDate(src)) return null
 const date = new Date(src.getTime())
 date.setHours(0, 0, 0, 0)
 // Thursday in current week decides the year.
 date.setDate(date.getDate() + 3 - (date.getDay() + 6) % 7)
 // January 4 is always in week 1.
 const week1 = new Date(date.getFullYear(), 0, 4)
 // Adjust to Thursday in week 1 and count number of weeks from date to week 1.
 // Rounding should be fine for Daylight Saving Time. Its shift should never be more than 12 hours.
 return 1 + Math.round(((date.getTime() - week1.getTime()) / 86400000 - 3 + (week1.getDay() + 6) % 7) / 7)
}

export const getRangeHours = function(ranges) {
 const hours = []
 let disabledHours = [];

 (ranges || []).forEach(range => {
 const value = range.map(date => date.getHours())

 disabledHours = disabledHours.concat(newArray(value[0], value[1]))
 })

 if (disabledHours.length) {
 for (let i = 0; i < 24; i++) {
 hours[i] = disabledHours.indexOf(i) === -1
 }
 } else {
 for (let i = 0; i < 24; i++) {
 hours[i] = false
 }
 }

 return hours
}

export const getPrevMonthLastDays = (date, amount) => {
 if (amount <= 0) return []
 const temp = new Date(date.getTime())
 temp.setDate(0)
 const lastDay = temp.getDate()
 return range(amount).map((_, index) => lastDay - (amount - index - 1))
}

export const getMonthDays = (date) => {
 const temp = new Date(date.getFullYear(), date.getMonth() + 1, 0)
 const days = temp.getDate()
 return range(days).map((_, index) => index + 1)
}

function setRangeData(arr, start, end, value) {
 for (let i = start; i < end; i++) {
 arr[i] = value
 }
}

export const getRangeMinutes = function(ranges, hour) {
 const minutes = new Array(60)

 if (ranges.length > 0) {
 ranges.forEach(range => {
 const start = range[0]
 const end = range[1]
 const startHour = start.getHours()
 const startMinute = start.getMinutes()
 const endHour = end.getHours()
 const endMinute = end.getMinutes()
 if (startHour === hour && endHour !== hour) {
 setRangeData(minutes, startMinute, 60, true)
 } else if (startHour === hour && endHour === hour) {
 setRangeData(minutes, startMinute, endMinute + 1, true)
 } else if (startHour !== hour && endHour === hour) {
 setRangeData(minutes, 0, endMinute + 1, true)
 } else if (startHour < hour && endHour > hour) {
 setRangeData(minutes, 0, 60, true)
 }
 })
 } else {
 setRangeData(minutes, 0, 60, true)
 }
 return minutes
}

export const range = function(n) {
 // see https://stackoverflow.com/questions/3746725/create-a-javascript-array-containing-1-n
 return Array.apply(null, {length: n}).map((_, n) => n)
}

export const modifyDate = function(date, y, m, d) {
 return new Date(y, m, d, date.getHours(), date.getMinutes(), date.getSeconds(), date.getMilliseconds())
}

export const modifyTime = function(date, h, m, s) {
 return new Date(date.getFullYear(), date.getMonth(), date.getDate(), h, m, s, date.getMilliseconds())
}

export const modifyWithTimeString = (date, time) => {
 if (date == null || !time) {
 return date
 }
 time = parseDate(time, 'HH:mm:ss')
 return modifyTime(date, time.getHours(), time.getMinutes(), time.getSeconds())
}

export const clearTime = function(date) {
 return new Date(date.getFullYear(), date.getMonth(), date.getDate())
}

export const clearMilliseconds = function(date) {
 return new Date(date.getFullYear(), date.getMonth(), date.getDate(), date.getHours(), date.getMinutes(), date.getSeconds(), 0)
}

export const limitTimeRange = function(date, ranges, format = 'HH:mm:ss') {
 // TODO: refactory a more elegant solution
 if (ranges.length === 0) return date
 const normalizeDate = date => fecha.parse(fecha.format(date, format), format)
 const ndate = normalizeDate(date)
 const nranges = ranges.map(range => range.map(normalizeDate))
 if (nranges.some(nrange => ndate >= nrange[0] && ndate <= nrange[1])) return date

 let minDate = nranges[0][0]
 let maxDate = nranges[0][0]

 nranges.forEach(nrange => {
 minDate = new Date(Math.min(nrange[0], minDate))
 maxDate = new Date(Math.max(nrange[1], minDate))
 })

 const ret = ndate < minDate ? minDate : maxDate
 // preserve Year/Month/Date
 return modifyDate(
 ret,
 date.getFullYear(),
 date.getMonth(),
 date.getDate()
 )
}

export const timeWithinRange = function(date, selectableRange, format) {
 const limitedDate = limitTimeRange(date, selectableRange, format)
 return limitedDate.getTime() === date.getTime()
}

export const changeYearMonthAndClampDate = function(date, year, month) {
 // clamp date to the number of days in `year`, `month`
 // eg: (2010年1月31日, 2010, 2) => 2010年2月28日
 const monthDate = Math.min(date.getDate(), getDayCountOfMonth(year, month))
 return modifyDate(date, year, month, monthDate)
}

export const prevMonth = function(date) {
 const year = date.getFullYear()
 const month = date.getMonth()
 return month === 0
 ? changeYearMonthAndClampDate(date, year - 1, 11)
 : changeYearMonthAndClampDate(date, year, month - 1)
}

export const nextMonth = function(date) {
 const year = date.getFullYear()
 const month = date.getMonth()
 return month === 11
 ? changeYearMonthAndClampDate(date, year + 1, 0)
 : changeYearMonthAndClampDate(date, year, month + 1)
}

export const prevYear = function(date, amount = 1) {
 const year = date.getFullYear()
 const month = date.getMonth()
 return changeYearMonthAndClampDate(date, year - amount, month)
}

export const nextYear = function(date, amount = 1) {
 const year = date.getFullYear()
 const month = date.getMonth()
 return changeYearMonthAndClampDate(date, year + amount, month)
}

export const extractDateFormat = function(format) {
 return format
 .replace(/\W?m{1,2}|\W?ZZ/g, '')
 .replace(/\W?h{1,2}|\W?s{1,3}|\W?a/gi, '')
 .trim()
}

export const extractTimeFormat = function(format) {
 return format
 .replace(/\W?D{1,2}|\W?Do|\W?d{1,4}|\W?M{1,4}|\W?y{2,4}/g, '')
 .trim()
}

export const validateRangeInOneMonth = function(start, end) {
 return (start.getMonth() === end.getMonth()) && (start.getFullYear() === end.getFullYear())
}