/**
 * Page navigation controller for the PDF viewer.
 *
 * Manages the page number input, previous/next buttons, and tracks
 * the currently visible page using an `IntersectionObserver`.
 * When the user scrolls, the observer detects which page is centered
 * in the viewport and updates the navigation state accordingly.
 */
export default class PageNav {
    /** Input field displaying and accepting the current page number. */
    private readonly pageInput;
    /** Span element showing the total number of pages. */
    private readonly totalPage;
    /** Button to navigate to the previous page. */
    private readonly prevPageButton;
    /** Button to navigate to the next page. */
    private readonly nextPageButton;
    /** The scrollable page view container. */
    private readonly pageView;
    /** All rendered page DOM nodes in document order. */
    private readonly pageNodes;
    /** Form element wrapping the page number input. */
    private readonly pageForm;
    /** Minimum valid page number (always 1). */
    private readonly minPage;
    /** Maximum valid page number (equals total pages). */
    private readonly maxPage;
    /** Last known valid page number, used as a fallback for invalid input. */
    private lastPage;
    /** Callback invoked when the currently visible page changes. */
    private changeListener;
    /**
     * Initializes page navigation by querying dependent DOM nodes,
     * setting up the `IntersectionObserver`, and binding event listeners.
     *
     * @param context    - The root element containing all navigation-related elements.
     * @param pageNumber - The total number of pages in the document.
     */
    constructor(context: HTMLElement, pageNumber: number);
    /**
     * Scrolls to the specified page and updates the navigation state.
     *
     * @param pageNum - The 1-based page number to navigate to.
     */
    activatePage(pageNum: number): void;
    /**
     * Updates the page input value and button disabled states to reflect the given page number.
     *
     * @param pageNum - The 1-based page number to display.
     */
    private updatePage;
    /**
     * Parses the page number from the input field, clamps it to the valid range,
     * and navigates to the resulting page. If the input is not a valid number,
     * it is reverted to the last known valid page.
     */
    private enterPage;
    /**
     * Registers a callback that is invoked whenever the visible page changes.
     *
     * @param listener - Callback receiving the 1-based page number of the currently visible page.
     * @returns This instance for chaining.
     */
    onChange(listener: (pageNum: number) => void): PageNav;
    /**
     * Returns the page number currently displayed in the navigation input.
     *
     * @returns The current 1-based page number.
     */
    getCurrentPageNumber(): number;
}