day-of-year.js

import { addFormatToken } from '../format/format';
import { addUnitAlias } from './aliases';
import { addRegexToken, match3, match1to3 } from '../parse/regex';
import { daysInYear } from './year';
import { createUTCDate } from '../create/date-from-array';
import { addParseToken } from '../parse/token';
import toInt from '../utils/to-int';

// FORMATTING

addFormatToken('DDD', ['DDDD', 3], 'DDDo', 'dayOfYear');

// ALIASES

addUnitAlias('dayOfYear', 'DDD');

// PARSING

addRegexToken('DDD',  match1to3);
addRegexToken('DDDD', match3);
addParseToken(['DDD', 'DDDD'], function (input, array, config) {
    config._dayOfYear = toInt(input);
});

// HELPERS

//http://en.wikipedia.org/wiki/ISO_week_date#Calculating_a_date_given_the_year.2C_week_number_and_weekday
export function dayOfYearFromWeeks(year, week, weekday, firstDayOfWeekOfYear, firstDayOfWeek) {
    var week1Jan = 6 + firstDayOfWeek - firstDayOfWeekOfYear, janX = createUTCDate(year, 0, 1 + week1Jan), d = janX.getUTCDay(), dayOfYear;
    if (d < firstDayOfWeek) {
        d += 7;
    }

    weekday = weekday != null ? 1 * weekday : firstDayOfWeek;

    dayOfYear = 1 + week1Jan + 7 * (week - 1) - d + weekday;

    return {
        year: dayOfYear > 0 ? year : year - 1,
        dayOfYear: dayOfYear > 0 ?  dayOfYear : daysInYear(year - 1) + dayOfYear
    };
}

// MOMENTS

export function getSetDayOfYear (input) {
    var dayOfYear = Math.round((this.clone().startOf('day') - this.clone().startOf('year')) / 864e5) + 1;
    return input == null ? dayOfYear : this.add((input - dayOfYear), 'd');
}