export interface UseCountUpOptions {
    /** Target value the animation lands on. */
    to: number;
    /** Starting value. Defaults to 0. */
    from?: number;
    /** Duration in milliseconds. Defaults to 1600. */
    durationMs?: number;
    /**
     * Attach an `IntersectionObserver` to the ref and only start the
     * animation when the element first crosses the visibility threshold.
     * Defaults to `true`. Set to `false` to start immediately on mount.
     */
    startOnVisible?: boolean;
    /**
     * When `true`, every out-of-view → in-view transition resets to
     * `from` and re-plays the animation. Defaults to `false` — the
     * default is "animate once per element per session", matching the
     * booking-website hero use-case.
     */
    retriggerOnReEntry?: boolean;
    /** BCP 47 locale. Falls back to `navigator.language` then `'en'`. */
    locale?: string;
    /**
     * Override the locale's default thousand / decimal glyphs. When set,
     * the hook builds a custom formatter on top of `Intl.NumberFormat`
     * via `formatToParts`. Pass partial overrides — `decimal` alone is
     * valid; the unspecified separator stays at the locale default.
     */
    separators?: {
        thousand?: string;
        decimal?: string;
    };
    /**
     * Full override — when provided, the hook bypasses
     * `Intl.NumberFormat` and runs every frame's numeric value through
     * this function instead. Highest precedence; `locale` and
     * `separators` are ignored for the duration of the animation. The
     * sign is part of the number passed in.
     */
    formatter?: (n: number) => string;
    /**
     * Forces the reduced-motion branch on. Defaults to reading
     * `prefers-reduced-motion: reduce` via `window.matchMedia`. Useful
     * for unit tests and for callers that already track motion
     * preferences upstream.
     */
    reduceMotion?: boolean;
}
export interface UseCountUpReturn {
    /**
     * Ref callback. Attach to the element that should trigger the
     * animation on viewport entry. Passing `null` (unmounting) cleans
     * up the IntersectionObserver.
     */
    ref: (el: HTMLElement | null) => void;
    /** Formatted current frame value. */
    value: string;
    /** `true` after the animation lands on `to`. */
    done: boolean;
    /**
     * Manually start the animation. Useful when `startOnVisible` is
     * `false` or when re-playing is gated on a non-viewport event.
     */
    start: () => void;
    /** Reset to `from`; the next `start` (or visibility entry) re-plays. */
    reset: () => void;
}
/**
 * Animate a number from `from` to `to` over `durationMs`, optionally
 * gated on viewport entry. Uses raw `requestAnimationFrame` + an
 * `IntersectionObserver`, no third-party dependency.
 *
 * SSR-safe — the first render (server + client first-paint) returns the
 * final formatted value. The IntersectionObserver and the rAF loop are
 * attached inside `useEffect` so SSR markup matches client first-paint
 * and hydration never observes the `from` value.
 *
 * Reduced motion — when `prefers-reduced-motion: reduce` is active (or
 * `reduceMotion: true` is passed) the hook short-circuits to the final
 * value on first paint and never attaches the observer. Honoured even
 * when `retriggerOnReEntry` is set.
 *
 * Direction & negatives — the hook animates from `from` to `to`
 * whichever direction that is. `to` can be negative; the sign is part
 * of the formatted output every frame.
 */
export declare function useCountUp(options: UseCountUpOptions): UseCountUpReturn;
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