import type { SyncItem } from '../contentful/types';
import { Syncable } from '../syncEngine';
export interface Exportable {
    /**
     * Exports the current state of the data source to a backup key-value store
     */
    export(): Generator<SyncItem, void, void> | AsyncGenerator<SyncItem, void, void>;
}
/**
 * The writable part of the AsyncStorage interface
 */
export interface WritableKeyValueStorage {
    setItem: (key: string, value: string) => Promise<void>;
}
/**
 * The readable part of the AsyncStorage interface
 */
export interface ReadableKeyValueStorage {
    getItem: (key: string) => Promise<string | null>;
}
/**
 *
 */
export interface DataSourceWithBackup {
    backup(): Promise<void>;
    restore(): Promise<void>;
}
/**
 * Enhances a DataSource with AsyncStorage to make a convenient backup and
 * restore system.
 * @param dataSource The data source with canonical data eg InMemoryDataSource
 * @param storage A Key-Value Pair storage system like AsyncStorage
 * @param prefix The key prefix under which to store the data
 * @returns The same DataSource enhanced with the backup() and restore() methods
 */
export declare function addBackup<TDataSource extends Exportable & Syncable>(dataSource: TDataSource, storage: WritableKeyValueStorage & ReadableKeyValueStorage, prefix: string): asserts dataSource is TDataSource & DataSourceWithBackup;
/**
 * Enhances a DataSource with AsyncStorage to make a convenient backup and
 * restore system.
 * @param dataSource The data source with canonical data eg InMemoryDataSource
 * @param storage A Key-Value Pair storage system like AsyncStorage
 * @param prefix The key prefix under which to store the data
 * @returns The same DataSource enhanced with the backup() and restore() methods
 */
export declare function withBackup<TDataSource extends Exportable & Syncable>(dataSource: TDataSource, storage: WritableKeyValueStorage & ReadableKeyValueStorage, prefix: string): TDataSource & DataSourceWithBackup;
export declare function isExportable(dataSource: any): dataSource is Exportable;
export declare function hasBackup(dataSource: any): dataSource is DataSourceWithBackup;