/**
 * @module botbuilder
 */
/**
 * Copyright (c) Microsoft Corporation. All rights reserved.
 * Licensed under the MIT License.
 */
import { TurnContext, Middleware } from 'botbuilder-core';
import { Storage, StoreItem, StorageKeyFactory } from './storage';
/**
 * State information cached off the context object by a `BotState` instance.
 */
export interface CachedBotState<T extends StoreItem> {
    state: T;
    hash: string;
}
/**
 * Reads and writes state for your bot to storage.
 *
 * @remarks
 * The state object will be automatically cached on the context object for the lifetime of the turn
 * and will only be written to storage if it has been modified.
 *
 * When a `BotState` instance is used as middleware its state object will be automatically read in
 * before your bots logic runs and then intelligently written back out upon completion of your bots
 * logic. Multiple instances can be read and written in parallel using the `BotStateSet` middleware.
 *
 * ```JavaScript
 * const { BotState, MemoryStorage } = require('botbuilder');
 *
 * const storage = new MemoryStorage();
 * const botState = new BotState(storage, (context) => 'botState');
 * adapter.use(botState);
 *
 * server.post('/api/messages', (req, res) => {
 *    adapter.processActivity(req, res, async (context) => {
 *       // Track up time
 *       const state = botState.get(context);
 *       if (!('startTime' in state)) { state.startTime = new Date().getTime() }
 *       state.upTime = new Date().getTime() - state.stateTime;
 *
 *       // ... route activity ...
 *
 *    });
 * });
 * ```
 */
export declare class BotState<T extends StoreItem = StoreItem> implements Middleware {
    protected storage: Storage;
    protected storageKey: StorageKeyFactory;
    private stateKey;
    /**
     * Creates a new BotState instance.
     * @param storage Storage provider to persist the state object to.
     * @param storageKey Function called anytime the storage key for a given turn needs to be calculated.
     */
    constructor(storage: Storage, storageKey: StorageKeyFactory);
    onTurn(context: TurnContext, next: () => Promise<void>): Promise<void>;
    /**
     * Reads in and caches the current state object for a turn.
     *
     * @remarks
     * Subsequent reads will return the cached object unless the `force` flag is passed in which
     * will force the state object to be re-read.
     *
     * ```JavaScript
     * const state = await botState.read(context);
     * ```
     * @param context Context for current turn of conversation with the user.
     * @param force (Optional) If `true` the cache will be bypassed and the state will always be read in directly from storage. Defaults to `false`.
     */
    read(context: TurnContext, force?: boolean): Promise<T>;
    /**
     * Saves the cached state object if it's been changed.
     *
     * @remarks
     * If the `force` flag is passed in the cached state object will be saved regardless of
     * whether its been changed or not and if no object has been cached, an empty object will be
     * created and then saved.
     *
     * ```JavaScript
     * await botState.write(context);
     * ```
     * @param context Context for current turn of conversation with the user.
     * @param force (Optional) if `true` the state will always be written out regardless of its change state. Defaults to `false`.
     */
    write(context: TurnContext, force?: boolean): Promise<void>;
    /**
     * Clears the current state object for a turn.
     *
     * @remarks
     * This example shows how to clear a state object:
     *
     * ```JavaScript
     * botState.clear(context);
     * ```
     * @param context Context for current turn of conversation with the user.
     */
    clear(context: TurnContext): void;
    /**
     * Returns a cached state object or undefined if not cached.
     *
     * @remarks
     * This example shows how to synchronously get an already loaded and cached state object:
     *
     * ```JavaScript
     * const state botState.get(context);
     * ```
     * @param context Context for current turn of conversation with the user.
     */
    get(context: TurnContext): T | undefined;
}