/**
 * Single source of truth for parsing and matching blackout dates across the
 * datepicker. Both `auro-calendar` (memoized Set + `isDateBlackout`) and the
 * pre-`firstUpdated` fallback inside `auro-calendar-cell` route through these
 * helpers so the YYYY-MM-DD → seconds conversion and the merge-with-legacy
 * `disabledDays` rules are defined exactly once.
 */
/**
 * Converts a `YYYY-MM-DD` ISO date string to a Unix timestamp (seconds)
 * representing local midnight on that calendar day. Returns `null` for
 * inputs that don't parse to a finite timestamp.
 *
 * Uses the `new Date(year, monthIndex, day)` constructor (NOT
 * `new Date(isoStr)`) so the result is local-midnight rather than UTC
 * midnight — required to keep the calendar grid aligned with the user's
 * local calendar day in negative-offset timezones.
 *
 * @param {string} isoStr - Date string in `YYYY-MM-DD` format.
 * @returns {number|null} Local-midnight Unix timestamp (seconds), or null.
 */
export function parseIsoToTimestamp(isoStr: string): number | null;
/**
 * Builds a `Set<number>` of seconds-since-epoch timestamps covering both the
 * legacy `disabledDays` (already-numeric) array and the ISO `blackoutDates`
 * array. Use this for O(1) membership checks in hot paths.
 *
 * @param {Array<string|number>|undefined} disabledDays - Legacy timestamp array.
 * @param {Array<string>|undefined} blackoutDates - ISO `YYYY-MM-DD` array.
 * @returns {Set<number>}
 */
export function buildBlackoutSet(disabledDays: Array<string | number> | undefined, blackoutDates: Array<string> | undefined): Set<number>;
/**
 * One-shot membership test for a single timestamp against both blackout
 * sources. Allocates a Set on each call; only use this in cold paths
 * (e.g. the pre-`firstUpdated` cell fallback). Hot paths should hold the
 * Set returned from `buildBlackoutSet` and `.has(ts)` directly.
 *
 * @param {number} dateTs - Unix timestamp (seconds) to test.
 * @param {Array<string|number>|undefined} disabledDays - Legacy timestamp array.
 * @param {Array<string>|undefined} blackoutDates - ISO `YYYY-MM-DD` array.
 * @returns {boolean}
 */
export function isBlackoutTimestamp(dateTs: number, disabledDays: Array<string | number> | undefined, blackoutDates: Array<string> | undefined): boolean;