/**
 * Date formatting and parsing utilities for DatePicker.
 * Uses native Intl.DateTimeFormat — no external dependencies.
 *
 * @internal Engine functions are an internal API of the DatePicker
 * component. They are exported for testing and re-use by sibling
 * components in this package but are not part of the public surface;
 * the supported entry points are the `DatePicker` and `DateRangePicker`
 * Svelte components themselves.
 */
import type { DateRange } from '../Calendar/calendar.types.js';
export type DateFormatOptions = Intl.DateTimeFormatOptions;
/**
 * Format a Date as a locale-aware string. Guards Invalid Date and Intl
 * errors with logging instead of silent fallback.
 */
export declare function formatDateInput(date: Date, locale: string, options?: DateFormatOptions): string;
/**
 * Format a date range. Deliberately concatenates the two halves with a
 * fixed " – " (U+2013, en-dash with spaces) separator instead of
 * `Intl.DateTimeFormat#formatRange`. The native API would collapse
 * shared components (year/month) and break round-trip parsing — the
 * range "Mar 15 – 22, 2026" cannot be split back into two valid dates
 * because the first half has no year. The fixed separator keeps
 * `formatDateRangeInput` and `parseDateRangeInput` symmetric.
 */
export declare function formatDateRangeInput(start: Date, end: Date, locale: string, options?: DateFormatOptions): string;
/**
 * Parse a single date from user input. Tries the locale's formatted mask
 * first (built via `Intl.DateTimeFormat#formatToParts`), then a strict
 * YYYY-MM-DD ISO fallback parsed in LOCAL timezone. Returns `null` for
 * anything that can't be unambiguously parsed.
 *
 * Supports any locale whose default mask is purely numeric (day, month,
 * year). Locales with non-numeric month names (`month: 'long'`),
 * weekday literals, or non-Gregorian calendars are NOT parseable — the
 * caller should rely on calendar-picker UX or accept ISO input only.
 */
export declare function parseDateInput(input: string, locale: string, options?: DateFormatOptions): Date | null;
/**
 * Parse a date range string like "15.03.2026 – 22.03.2026". Splits on
 * the locale-aware range separator and parses each half with `parseDateInput`.
 * A single date with no separator is accepted as a single-day range
 * (`{ start: d, end: d }`). Rejects inverted ranges (start after end).
 */
export declare function parseDateRangeInput(input: string, locale: string, options?: DateFormatOptions): DateRange | null;
export interface DateConstraints {
    minDate?: Date;
    maxDate?: Date;
    disabledDates?: Date[];
    isDateDisabled?: (date: Date) => boolean;
}
/**
 * Centralised predicate that respects min/max/disabledDates/isDateDisabled.
 * Used by both calendar clicks and typed input so they validate identically.
 *
 * Defensive against bad inputs:
 * - Invalid `minDate` / `maxDate` are ignored with a warning instead of
 *   silently disabling the constraint.
 * - Invalid entries in `disabledDates` are skipped with a warning.
 * - Throws from `isDateDisabled` are caught and logged; the date is
 *   then treated as allowed so a faulty predicate can't take the picker
 *   down.
 *
 * Note: if `minDate > maxDate` after stripping time, every date is
 * out-of-range. We warn once on that configuration to surface the bug.
 */
export declare function isDateAllowed(date: Date, constraints: DateConstraints): boolean;