digitransit-ui/app/util/dateSelectUtils.js

import { DateTime } from 'luxon';

/**
 * Generate human-readable label for a date.
 * Returns "Today", "Tomorrow", or formatted date (e.g., "Mon 15.1.").
 *
 * @param {DateTime} date - Date to label
 * @param {DateTime} today - Today's date for comparison
 * @param {DateTime} tomorrow - Tomorrow's date for comparison
 * @param {Object} intl - Internationalization object with formatMessage
 * @returns {string} Formatted label
 */
export function formatDateLabel(date, today, tomorrow, intl) {
  const isToday = date.hasSame(today, 'day');
  const isTomorrow = date.hasSame(tomorrow, 'day');

  if (isToday) {
    return intl.formatMessage({ id: 'today', defaultMessage: 'Today' });
  }
  if (isTomorrow) {
    return intl.formatMessage({ id: 'tomorrow', defaultMessage: 'Tomorrow' });
  }
  return date.toFormat('ccc d.L.');
}

/**
 * Generate week group label ("This week", "Next week", or "Week N").
 *
 * @param {number} weekNum - Week number
 * @param {number} currentWeek - Current week number
 * @param {Object} intl - Internationalization object with formatMessage
 * @returns {string} Formatted group label
 */
export function formatWeekLabel(weekNum, currentWeek, intl) {
  if (weekNum === currentWeek) {
    return intl.formatMessage({ id: 'this-week', defaultMessage: 'This week' });
  }
  if (weekNum === currentWeek + 1) {
    return intl.formatMessage({ id: 'next-week', defaultMessage: 'Next week' });
  }
  return intl.formatMessage(
    { id: 'week-number', defaultMessage: 'Week {number}' },
    { number: weekNum },
  );
}

/**
 * Process dates into option objects with labels and formatting.
 *
 * @param {Array<DateTime>} dates - Array of Luxon DateTime objects
 * @param {DateTime} today - Today's date for comparison
 * @param {DateTime} tomorrow - Tomorrow's date for comparison
 * @param {string} dateFormat - Format string for DateTime conversion
 * @param {Object} intl - Internationalization object
 * @returns {Array<Object>} Array of date objects with value, textLabel, weekNumber, dateObj
 */
export function processDates(dates, today, tomorrow, dateFormat, intl) {
  return dates.map(d => ({
    dateObj: d,
    value: d.toFormat(dateFormat),
    textLabel: formatDateLabel(d, today, tomorrow, intl),
    // accessibility label with full weekday
    ariaLabel: d.toFormat('EEEE d.L.'),
    weekNumber: d.weekNumber,
  }));
}

/**
 * Group dates by week number.
 *
 * @param {Array<Object>} processedDates - Array of processed date objects
 * @param {number} currentWeek - Current week number
 * @param {Object} intl - Internationalization object
 * @returns {Array<Object>} Array of grouped options with label and options
 */
export function groupDatesByWeek(processedDates, currentWeek, intl) {
  const byWeek = processedDates.reduce((acc, item) => {
    if (!acc[item.weekNumber]) {
      acc[item.weekNumber] = [];
    }
    acc[item.weekNumber].push(item);
    return acc;
  }, {});

  const groupedOptions = [];
  Object.entries(byWeek)
    .sort(([a], [b]) => Number(a) - Number(b))
    .forEach(([weekNum, weekItems]) => {
      const groupLabel = formatWeekLabel(Number(weekNum), currentWeek, intl);

      groupedOptions.push({ label: groupLabel, options: weekItems });
    });

  return groupedOptions;
}

/**
 * Generate a range of future dates starting from a given date.
 *
 * @param {DateTime} startDate - Starting date (must be valid Luxon DateTime)
 * @param {number} numberOfDays - Number of days to generate
 * @param {string} locale - Locale string for date formatting
 * @returns {Array<DateTime>} Array of Luxon DateTime objects
 */
export function generateDateRange(startDate, numberOfDays, locale) {
  const normalizedStart = startDate.setLocale(locale).startOf('day');

  return Array.from({ length: numberOfDays }, (_, i) =>
    normalizedStart.plus({ days: i }),
  );
}

/**
 * Extract selected value from DateTime object.
 *
 * @param {DateTime} selectedDay - Selected day as a Luxon DateTime
 * @param {string} dateFormat - Format string for DateTime conversion
 * @returns {string|undefined} Formatted date string or undefined
 */
export function extractSelectedValue(selectedDay, dateFormat) {
  if (selectedDay && selectedDay instanceof DateTime && selectedDay.isValid) {
    return selectedDay.toFormat(dateFormat);
  }
  return undefined;
}