import { FeedEntry } from "./feed_entry";
import { FeedStore } from "./feed_store";
/**
 * Stores feed data to a sheet of Google Spreadsheet.
 * The first row is used for an marker and metadata.
 * The feeds are stored to second or later rows.
 */
export declare class SpreadsheetStore implements FeedStore {
    readonly spreadsheetId: string;
    readonly sheetName: string;
    static readonly ETAG_POSITION = 3;
    private static readonly FEED_MARK;
    private static readonly DATA_VERSION;
    private readonly sheet;
    /**
     * Create a new SpreadsheetStore.
     *
     * @param spreadsheetId - An ID of spreadsheet.
     * @param sheetName - A name of sheet.
     */
    constructor(spreadsheetId: string, sheetName: string);
    /**
     * Load stored ETag data.
     * Returns an empty string when there is no stored data.
     *
     * @returns ETag.
     */
    loadETag(): string;
    /**
     * Save the ETag data.
     *
     * @param etag - ETag.
     */
    saveETag(etag: string): void;
    /**
     * Get the feed count of store.
     *
     * @returns feed count.
     */
    getFeedCount(): number;
    /**
     * Load the latest n feeds.
     *
     * @param n - Count of feeds.
     * @returns Loaded feeds.
     */
    loadFeeds(n: number): FeedEntry[];
    /**
     * Save new feeds.
     * This does not care the feed's ID.
     * Always stored all feeds.
     *
     * @param feeds - Feeds to save.
     */
    saveFeeds(feeds: FeedEntry[]): void;
    /**
     * Return true if there is no feeds in this store.
     *
     * @returns Store is empty or not.
     */
    isEmpty(): boolean;
    /**
     * Clear all stored feeds.
     */
    clear(): void;
    private initialize;
    private isInitialized;
    private getSheet;
}