import { ReplyItem } from '../reply';
export declare class RepliesOrder {
    private _groupBy;
    private _orderBy;
    private _orderDirection;
    /**
     * every action to change filter will stream change event.
     */
    private changeEvent;
    readonly onChange: import("rxjs/internal/Observable").Observable<any>;
    groupBy: string;
    orderBy: "timestamp" | "displayName" | "phoneNumber" | "email";
    orderDirection: import("firebase").firestore.OrderByDirection;
    empty(): void;
    getGroupKeyValue(reply: ReplyItem): string;
    getOrderKeyValue(reply: ReplyItem): string;
    private _getOrderKeyValue;
}