@financial-times/n-conversion-forms/helpers/duration-helpers.js

Containing jsx components and styles for forms included on Accounts and Acquisition apps (next-signup, next-profile, next-retention, etc).

/**
 * Returns period converted to time if found
 * otherwise returns empty string to avoid show information not mapped.
 * @param {string} iso8601Value: PxY (yearly), PxM (montly), PxW (weekly), of PxD (daily), where x is the amount of years/months/weeks/days
 * @param {boolean} excludeAmountWhenSingular: Omits the amount from the returned string when the discerned amount is singular.
 * @returns {string}
 */
const getDurationFromISO8601Value = ({
	iso8601Value,
	excludeAmountWhenSingular = true,
}) => {
	const amount = iso8601Value.substring(1, iso8601Value.length - 1);

	const PERIOD_UNIT_CODE_TO_PLURAL_TERM_MAP = {
		Y: 'years',
		M: 'months',
		W: 'weeks',
		D: 'days',
	};

	const PERIOD_UNIT_CODE_TO_SINGULAR_TERM_MAP = {
		Y: 'year',
		M: 'month',
		W: 'week',
		D: 'day',
	};

	const periodUnitCode = iso8601Value.substring(iso8601Value.length - 1);

	if (iso8601Value) {
		const unit =
			amount === '1'
				? PERIOD_UNIT_CODE_TO_SINGULAR_TERM_MAP[periodUnitCode] || ''
				: PERIOD_UNIT_CODE_TO_PLURAL_TERM_MAP[periodUnitCode] || '';

		return amount === '1' && excludeAmountWhenSingular
			? unit
			: `${amount} ${unit}`;
	}

	return '';
};

const DAYS_IN_A_YEAR = 365; // Disregarding leap years
const DAYS_IN_A_MONTH = 30; // Approximate
const DAYS_IN_A_WEEK = 7;

const DAYS_IN_90_DAYS = 90;
const DAYS_IN_52_WEEKS = 52 * DAYS_IN_A_WEEK;

/**
 * Parses an ISO 8601 duration string and converts it into an approximate total number of days.
 * @param {string} iso8601Duration: PxY (yearly), PxM (monthly), PxW (weekly), or PxD (daily), where x is the amount.
 * @returns {number|null} Total number of days represented by the duration or null if the input is not a valid ISO 8601 duration.
 */
const parseISODurationToDays = (iso8601Duration) => {
	const match = iso8601Duration.match(
		/^P(?:(\d+)Y)?(?:(\d+)M)?(?:(\d+)W)?(?:(\d+)D)?$/
	);

	if (!match) return null;

	const years = Number(match[1] ?? 0);
	const months = Number(match[2] ?? 0);
	const weeks = Number(match[3] ?? 0);
	const days = Number(match[4] ?? 0);

	return (
		years * DAYS_IN_A_YEAR +
		months * DAYS_IN_A_MONTH +
		weeks * DAYS_IN_A_WEEK +
		days
	);
};

/**
 * Approximate check of whether an ISO 8601 duration is 52 weeks or shorter.
 * @param {string} iso8601Duration
 * @returns {boolean}
 */
const is52WeeksOrLonger = (iso8601Duration) => {
	const totalDays = parseISODurationToDays(iso8601Duration);
	if (totalDays === null) return false;

	return totalDays >= DAYS_IN_52_WEEKS;
};

/**
 * Approximate check of whether an ISO 8601 duration is 90 days or longer.
 * @param {string} iso8601Duration
 * @returns {boolean}
 */
const is90DaysOrLonger = (iso8601Duration) => {
	const totalDays = parseISODurationToDays(iso8601Duration);
	if (totalDays === null) return false;

	return totalDays >= DAYS_IN_90_DAYS;
};

module.exports = {
	getDurationFromISO8601Value,
	is52WeeksOrLonger,
	is90DaysOrLonger,
};