@burglekitt/gmt/dist/internal/advanceToWeekday.js

Temporal-based date and time utilities with timezone support and polyfill integration

/**
 * Return the PlainDate for the next/previous occurrence of `dayOfWeek` relative to `date`.
 *
 * @param date starting PlainDate
 * @param dayOfWeek target ISO day of week (1-7)
 * @param direction 1 to search forward (next), -1 to search backward (previous)
 * @param inclusive when `date` already falls on `dayOfWeek`, return it as-is instead of
 *   advancing a full week
 * @returns PlainDate for the resolved weekday
 */
export function advanceToWeekday(date, dayOfWeek, direction, inclusive) {
    const current = date.dayOfWeek;
    if (current === dayOfWeek) {
        if (inclusive)
            return date;
        return date.add({ days: 7 * direction });
    }
    // Distance to the target weekday walking in `direction`, always 1-6 days since
    // current !== dayOfWeek here.
    const diff = direction === 1
        ? (dayOfWeek - current + 7) % 7
        : (current - dayOfWeek + 7) % 7;
    return date.add({ days: diff * direction });
}