import { AfterViewInit, ChangeDetectorRef, ElementRef, EventEmitter, OnChanges, OnDestroy, Renderer2, SimpleChanges, TemplateRef } from '@angular/core';
import * as i0 from "@angular/core";
export declare class UsaComboBoxItemTemplate {
    templateRef: TemplateRef<any>;
    constructor(templateRef: TemplateRef<any>);
    static ɵfac: i0.ɵɵFactoryDeclaration<UsaComboBoxItemTemplate, never>;
    static ɵdir: i0.ɵɵDirectiveDeclaration<UsaComboBoxItemTemplate, "[usa-combo-box-item-template]", never, {}, {}, never, never, false, never>;
}
export declare class UsaComboboxList implements AfterViewInit, OnDestroy, OnChanges {
    private el;
    private cdr;
    private renderer;
    private document;
    dropdownListBox: ElementRef<HTMLUListElement>;
    /** List of items to display in dropdown */
    items: any[];
    labelField: string;
    valueField: string;
    /** Provided custom template for displaying each item.
     * If none provided, then the label property of each item will be shown */
    customItemTemplate: UsaComboBoxItemTemplate;
    /**
     * HTML id value to attach to container element
     */
    listId: string;
    /**
     * If virtualScroll is enabled, a scrollEnd event
     * will be fired when user scrolls to last item in the list,
     * allowing clients to load in more data
     */
    virtualScroll: boolean;
    /**
     * Direction to display the dropdown box
     */
    direction: 'top' | 'bottom';
    /** Id of label for listbox */
    ariaLabelledBy: string;
    selectedItem: any;
    /**
     * Emitted when a value is selected from the dropdown list
     */
    selected: EventEmitter<any>;
    /**
     * Emitted when the user presses the up arrow key and focus
     * is on first item in dropdown list. This indicates to the client
     * that the dropdown list should close and focus should move
     * back to the combo box input field
     */
    focusInput: EventEmitter<any>;
    /**
     * Emitted when user has scrolled to the end of the dropdown list.
     * This event only fires if virtual scroll is enabled
     */
    scrollEnd: EventEmitter<any>;
    _focusedItem: {
        item: any;
        index: number;
        itemHtml: HTMLDataListElement;
    };
    /**
     * Referenced to currently highlighted item. Highlighted items have a dark
     * border around to draw attention to it, but do not necessarily have focus.
     * This can occur if focus is on input and the highlighted item is the item
     * that best matches input query.
     */
    _highlightedItem: {
        item: any;
        index: number;
        itemHtml: HTMLDataListElement;
    };
    /** List of functions to call to un-bind events registered through renderer.listen call */
    _eventListeners: (() => void)[];
    constructor(el: ElementRef, cdr: ChangeDetectorRef, renderer: Renderer2, document: any);
    trackByFn(index: number): number;
    ngAfterViewInit(): void;
    ngOnDestroy(): void;
    ngOnChanges(changes: SimpleChanges): void;
    selectItem(item: any): void;
    onFocus(item: any, index: number, itemHtml: HTMLDataListElement): void;
    /**
     * Handles keypress on combobox dropdown items
     * @param $event
     * @returns
     */
    onKeyDown($event: KeyboardEvent): void;
    /**
     * Focus on first element of combo-box dropdown
     */
    focusFirstElement(): void;
    focusLastElement(): void;
    focusHighlightedElement(): void;
    /**
     * Used by default template for rendering display value. If each item is
     * an object, get its given value property, otherwise, simply display the item
     */
    getRenderValue(item: any): any;
    /**
     * Public interface that allows components to highlight an item in dropdown
     * without moving focus to it. This simply adds a visible border to the item
     * and moves it to visible area of the dropdown
     */
    highlightItem(index: number): void;
    private registerEventHandlers;
    /**
     * Attaches mouseover event to each list element in the dropdown. Since the mouseover
     * event fires quite often, we attach it this way in the ts rather than through HTML
     * This coupled with changeDetectionStrategy of OnPush minimizes the amount
     * of necessary change detection triggers
     */
    private bindMouseOverListeners;
    /**
     * Adds scroll event binding if virtual scrolling is enabled.
     * This event listens for whether the user has scrolled to the last
     * item in the list or not. If so, it will fire an event
     * indicating that the user has scrolled to the end and more data
     * should be fetched
     * @returns
     */
    private bindScrollListener;
    private setDropdownDirection;
    private updateFocusedItem;
    static ɵfac: i0.ɵɵFactoryDeclaration<UsaComboboxList, never>;
    static ɵcmp: i0.ɵɵComponentDeclaration<UsaComboboxList, "usa-combo-box-list", never, { "items": { "alias": "items"; "required": false; }; "labelField": { "alias": "labelField"; "required": false; }; "valueField": { "alias": "valueField"; "required": false; }; "customItemTemplate": { "alias": "customItemTemplate"; "required": false; }; "listId": { "alias": "listId"; "required": false; }; "virtualScroll": { "alias": "virtualScroll"; "required": false; }; "direction": { "alias": "direction"; "required": false; }; "ariaLabelledBy": { "alias": "ariaLabelledBy"; "required": false; }; "selectedItem": { "alias": "selectedItem"; "required": false; }; }, { "selected": "selected"; "focusInput": "focusInput"; "scrollEnd": "scrollEnd"; }, never, never, false, never>;
}