import { LfI18n } from './i18n.service';
import { LfStorage } from './storage.service';
import * as i0 from "@angular/core";
/**
 * I18n key used to set the unload alert message.
 */
export declare const I18N_UNLOAD_ALERT_MESSAGE_KEY = "unloadAlertMessage";
/**
 * Service used to enable/disable a browser alert when the user reloads/leaves
 * the page. The user will be reminded that they might lose filled-in form data,
 * and they will be able to stay in the current page or confirm their leaving of
 * the page.
 */
export declare class LfUnloadAlert {
    /**
     * Event handler function to run `beforeunload`. It makes the browser display
     * an alert when the application's value is dirty.
     */
    private handler;
    /**
     * Variable that keeps track of the existence of an event listener for the
     * `beforeunload` event.
     */
    private _isEnabled;
    constructor(lfStorage: LfStorage, lfI18n: LfI18n);
    /**
     * Whether the browser alert for when the user reloads/leaves the page is
     * enabled.
     */
    get isEnabled(): boolean;
    /**
     * Enable a browser alert for when the user reloads/leaves the page. A custom
     * message may be passed, although most browsers will ignore it (in favour of
     * a default browser-specific message). Consecutive calls to this method
     * simply change the alert's message.
     * @param message Message to display on the alert (ignored by most browsers
     * except IE).
     */
    enable(): void;
    /**
     * Disable the browser alert for when the user reloads/leaves the page.
     * Consecutive calls to this method have no effect.
     */
    disable(): void;
    static ɵfac: i0.ɵɵFactoryDeclaration<LfUnloadAlert, [null, { optional: true; }]>;
    static ɵprov: i0.ɵɵInjectableDeclaration<LfUnloadAlert>;
}