botbuilder-core
Version:
Core components for Microsoft Bot Builder. Components in this library can run either in a browser or on the server.
169 lines • 6.88 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
exports.BotState = void 0;
/**
* @module botbuilder
*/
/**
* Copyright (c) Microsoft Corporation. All rights reserved.
* Licensed under the MIT License.
*/
const botStatePropertyAccessor_1 = require("./botStatePropertyAccessor");
const storage_1 = require("./storage");
/**
* Base class for the frameworks state persistance scopes.
*
* @remarks
* This class will read and write state, to a provided storage provider, for each turn of
* conversation with a user. Derived classes, like `ConversationState` and `UserState`, provide a
* `StorageKeyFactory` which is used to determine the key used to persist a given storage object.
*
* The state object thats loaded 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.
*/
class BotState {
/**
* 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, storageKey) {
this.storage = storage;
this.storageKey = storageKey;
this.stateKey = Symbol('state');
}
/**
* Creates a new property accessor for reading and writing an individual property to the bot
* states storage object.
*
* @template T The type of property to create. Defaults to `any` type.
* @param name Name of the property to add.
* @returns An accessor for the property.
*/
createProperty(name) {
const prop = new botStatePropertyAccessor_1.BotStatePropertyAccessor(this, name);
return prop;
}
/**
* Reads in and caches the backing 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.
*
* This method is automatically called on first access of any of created property accessors.
*
* ```JavaScript
* const state = await botState.load(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`.
* @returns {Promise<any>} The cached state.
*/
load(context, force = false) {
const cached = context.turnState.get(this.stateKey);
if (force || !cached || !cached.state) {
return Promise.resolve(this.storageKey(context)).then((key) => {
return this.storage.read([key]).then((items) => {
const state = items[key] || {};
const hash = (0, storage_1.calculateChangeHash)(state);
context.turnState.set(this.stateKey, { state: state, hash: hash });
return state;
});
});
}
return Promise.resolve(cached.state);
}
/**
* 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.saveChanges(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`.
* @returns {Promise<void>} A promise representing the async operation.
*/
saveChanges(context, force = false) {
let cached = context.turnState.get(this.stateKey);
if (force || (cached && cached.hash !== (0, storage_1.calculateChangeHash)(cached === null || cached === void 0 ? void 0 : cached.state))) {
return Promise.resolve(this.storageKey(context)).then((key) => {
if (!cached) {
cached = { state: {}, hash: '' };
}
cached.state.eTag = '*';
const changes = {};
changes[key] = cached.state;
return this.storage.write(changes).then(() => {
// Update change hash and cache
cached.hash = (0, storage_1.calculateChangeHash)(cached.state);
context.turnState.set(this.stateKey, cached);
});
});
}
return Promise.resolve();
}
/**
* Clears the current state object for a turn.
*
* @remarks
* The cleared state object will not be persisted until [saveChanges()](#savechanges) has
* been called.
*
* ```JavaScript
* await botState.clear(context);
* await botState.saveChanges(context);
* ```
* @param context Context for current turn of conversation with the user.
* @returns {Promise<void>} A promise representing the async operation.
*/
clear(context) {
// Just overwrite cached value with a new object and empty hash. The empty hash will force the
// changes to be saved.
context.turnState.set(this.stateKey, { state: {}, hash: '' });
return Promise.resolve();
}
/**
* Delete the backing state object for the current turn.
*
* @remarks
* The state object will be removed from storage if it exists. If the state object has been
* read in and cached, the cache will be cleared.
*
* ```JavaScript
* await botState.delete(context);
* ```
* @param context Context for current turn of conversation with the user.
* @returns {Promise<void>} A promise representing the async operation.
*/
delete(context) {
if (context.turnState.has(this.stateKey)) {
context.turnState.delete(this.stateKey);
}
return Promise.resolve(this.storageKey(context)).then((key) => this.storage.delete([key]));
}
/**
* 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.
* @returns A cached state object or undefined if not cached.
*/
get(context) {
const cached = context.turnState.get(this.stateKey);
return typeof cached === 'object' && typeof cached.state === 'object' ? cached.state : undefined;
}
}
exports.BotState = BotState;
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