import * as i0 from "@angular/core";
export interface HistoryData {
    html: string;
}
export declare class HistoryService<HistoryData> {
    history: HistoryData[];
    historyIndex: number;
    lastUndoData: HistoryData | null;
    add(data: HistoryData): void;
    addIfDataChanged: (data: HistoryData) => void;
    undo: () => HistoryData;
    redo: () => HistoryData;
    static ɵfac: i0.ɵɵFactoryDeclaration<HistoryService<any>, never>;
    static ɵprov: i0.ɵɵInjectableDeclaration<HistoryService<any>>;
}