import { Observable } from 'rxjs';
import { ScrollSpyOptions } from './models/scroll-spy-options';
import { SpyTarget } from './models/spy-target';
import { SpyTargetIsIntersectingEvent } from './models/spy-target-is-intersecting-event';
/**
 * Encapsulates the logic for scroll spy on a scrollable element (`scrollContainer`).
 *
 * Scroll spy uses the [Intersection Observer API](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API).
 *
 * Supports window resizing.
 *
 * Inspired by:
 * - https://grafikart.fr/tutoriels/scrollspy-js-page-491
 * - https://codepen.io/diaphragm/pen/bGNBVxw
 * - https://github.com/chefomar/angular-scroll-spy
 */
export declare class ScrollSpy {
    private readonly spyTargetIsIntersectingSubject$;
    /**
     * Is emitted when a spy-target has transitioned into a state of intersection (`isIntersecting: true`) or out of a state of intersection (`isIntersecting: false`).
     */
    readonly spyTargetIsIntersecting$: Observable<SpyTargetIsIntersectingEvent>;
    private resizeSubscription?;
    private spyTargets;
    private intersectionObserver;
    private readonly resizeDebounceTime;
    /**
     * Defines the (vertical) position of the IntersectionObserver line.
     * Value between `0` (at the top) and `100` (at the bottom).
     *
     * @todo (For a future version of ngx-scroll-spy) This property should be configured by the user.
     */
    private readonly offset;
    constructor({ scrollContainer }?: ScrollSpyOptions);
    /**
     * Adds a spy-target and starts to observe that target.
     */
    addTarget(spyTarget: SpyTarget): void;
    /**
     * Removes a spy-target and stops observing that target.
     */
    removeTarget(spyTarget: SpyTarget): void;
    /**
     * Stops observing all spy-targets and completes spyTargetIsIntersecting$ subject.
     */
    stopSpying(): void;
    /**
     * Initialize IntersectionObserver.
     */
    private initIntersectionObserver;
    /**
     * A function which is called when one or more spy-targets have transitioned into a state of intersection (`isIntersecting: true`) or out of a state of intersection (`isIntersecting: false`).
     */
    private intersectionObserverCallback;
}