Composite BotSocket Client & Friends

A Composite BotSocket Client implementation designed for easy expandability that's ready-to-go out of the box, and that comes packed with leafs that are ready to be composited.

The CompositeBSClient is based off the Composite design pattern.

Essentially, BSClientLeaf defines a series of functions that the CompositeBSClient calls on all registered leafs as part of its regular operations. By creating leafs that implement these methods, the functionality of the CompositeBSClient can be extended at ease, without the overhead that would come with using inheritance.

A collection of leafs are provided in this package to make it easy to quickly add standard functionality.

Feel free to make a PR to add new leafs to this collection, or to improve on existing implantation. We'd love to hear from you!

Here's an example of setting up a CompositeBSClient instance with some leafs:

const { EventEmitter } = require('events');

const CompositeBSClient = require('@zwerm/composite-bs-client/CompositeBSClient');

// region leafs
const TalkingLeaf = require('@zwerm/composite-bs-client/leafs/TalkingLeaf');
const CookieUserIdLeaf = require('@zwerm/composite-bs-client/leafs/userid/CookieUserIdLeaf');
const StaticTimezoneLeaf = require('@zwerm/composite-bs-client/leafs/timezone/StaticTimezoneLeaf');
const BrowserLocationLeaf = require('@zwerm/composite-bs-client/leafs/location/BrowserLocationLeaf');

const ToggleDisabledOnConnectLeaf = require('@zwerm/composite-bs-client/leafs/ToggleDisabledOnConnectLeaf');
const SendInputQueryOnFormSubmitLeaf = require('@zwerm/composite-bs-client/leafs/SendInputQueryOnFormSubmitLeaf');
const ScrollToBottomOnLetterLeaf = require('@zwerm/composite-bs-client/leafs/ScrollToBottomOnLetterLeaf');
const EmitStatusMessageEventsLeaf = require('@zwerm/composite-bs-client/leafs/EmitStatusMessageEventsLeaf');
const AutoReconnectLeaf = require('@zwerm/composite-bs-client/leafs/AutoReconnectLeaf');
const SendEventOnHandshakeLeaf = require('@zwerm/composite-bs-client/leafs/SendEventOnHandshakeLeaf');
// endregion

const statusEmitter = new EventEmitter();

statusEmitter.on(EmitStatusMessageEventsLeaf.E_STATUS_CONNECTING, ({ isReconnection }) => console.warn(`${isReconnection ? 're' : ''}connecting...`));
statusEmitter.on(EmitStatusMessageEventsLeaf.E_STATUS_CONNECT, () => console.log('connected'));
statusEmitter.on(EmitStatusMessageEventsLeaf.E_STATUS_DISCONNECT, () => console.warn('disconnected'));
statusEmitter.on(EmitStatusMessageEventsLeaf.E_STATUS_ERROR, () => console.error('unable to reconnect'));

statusEmitter.on(AutoReconnectLeaf.E_STATUS_RECONNECT_COUNTDOWN, ({ secondsUntilReconnect }) => console.log(`connection lost, retrying in ${secondsUntilReconnect}...`));

CompositeBSClient
    .newForZwermChat(
        'wss://chat.zwerm.io',
        'team-id',
        'bot-id',
        'channel-id'
    )
    .registerLeaf(new TalkingLeaf())
    .registerLeaf(new CookieUserIdLeaf())
    .registerLeaf(new StaticTimezoneLeaf(require('moment-timezone').tz.guess()))
    .registerLeaf(new BrowserLocationLeaf())
    .registerLeaf(new ToggleDisabledOnConnectLeaf(document.getElementById('#user-says')))
    .registerLeaf(new SendInputQueryOnFormSubmitLeaf(document.getElementById('#user-says-send'), document.getElementById('#user-says')))
    .registerLeaf(new ScrollToBottomOnLetterLeaf(document.getElementById('message-container')))
    .registerLeaf(new EmitStatusMessageEventsLeaf(statusEmitter))
    .registerLeaf(new AutoReconnectLeaf(statusEmitter))
    .registerLeaf(new SendEventOnHandshakeLeaf('WELCOME'))
    .connect();

The above example results in a CompositeBSClient that will...

• Speak messages from the server when possible. (TalkingLeaf)
• Persist the server-provided user id across page refreshers. (CookieUserIdLeaf)
• Include the timezone that the user is in in messages sent to the server, as guessed by moment-timezone. (StaticTimezoneLeaf)
• Include the location of the user, using the geolocation api. (BrowserLocationLeaf)
• Set the disabled state of a HTMLElement based on when the CompositeBSclient connects and disconnects from the server. (ToggleDisabledOnConnectLeaf)
• Send the value of an HTMLInputElement as a query when a HTMLFormElement is submitted. (SendInputQueryOnFormSubmitLeaf)
• Scroll to the bottom of a DOM element when a new StaMP letter is received. (ScrollToBottomOnLetterLeaf )
• Emit status messages about the CompositeBSClients connection to the BotSocket server as events. (EmitStatuMessageEventsLeaf)
• Attempt to automatically reconnect to the BotSocket server on disconnect, after a delay. (AutoReconnectLeaf)
• Sends an event message of 'WELCOME' once the CompositeBSClient has shaken hands with the server. (SendEventOnHandshakeLeaf)

Leafs on the wind

The leafs system is very simple and easy to use.

BSClientLeafs are registered to a CompositeBSClient instance, which calls methods on all registered leafs as part of its usual operations.

When a leaf is registered on a CompositeBSClient, it's given a reference to that client. This provides leafs with a means to call functions on the client they're registered to, expanding their functionality and potential.

These methods are all defined in the BSClientLeaf base class. When the CompositeBSClient goes to make a call on one of these methods, all the registered leafs are checked, and any that actually implement that method are called.

Leafs are called in the order that they are registered, with return values cascading down as the last parameter, allowing for each call to mutate the return value.

Because of the nature of objects in Javascript, you must take great care when mutating objects with leafs, as Object.assign won't merge child properties. This is also the reason why we strongly recommend you use our abstract leafs whenever possible & available for features that involve touching objects.

Here is a quick rundown on the methods defined in BSClientLeaf, and their common use cases:

register(compositeBSClient: CompositeBSClient): void

This method registers the leaf to the given CompositeBSClient.

This method should be used for handling initialisation actions, such as attaching event listeners.

Remember to call super.register(compositeBSClient), otherwise you risk your leaf not working properly.

deregister(): void

This method de-registers the leaf from the CompositeBSClient it's registered to.

This method should be used for handling unwinding actions, such as removing event listeners.

Remember to call super.deregister(), otherwise you risk your leaf not working properly.

preConnect(isReconnecting: boolean): void

This method is called by the CompositeBSClient before it tries to connect to the BotSocket server.

The isReconnecting: boolean parameter represents if the client is attempting to reconnect to the server, after having been previously disconnected.

This method doesn't return anything.

postConnect(): void

This method is called by the CompositeBSClient after it has successfully connected to the BotSocket server.

This method is called before handing is done with the BotSocket server, making it unsafe to send messages (event, query or otherwise) in this method.

This method takes no parameters.

This method doesn't return anything.

preDisconnect(disconnectCode: number): void

This method is called by the CompositeBSClient before it tries to disconnect from the BotSocket server.

The disconnectCode: number parameter represents the code that will provided as the reason for disconnection.

This method doesn't return anything.

postDisconnect(disconnectCode: number): void

This method is called by the CompositeBSClient after it has been disconnected from the BotSocket server.

The disconnectCode: number parameter represents the code that was provided as the reason for disconnection.

This method doesn't return anything.

errored(): void

This method is called by the CompositeBSClient when the socket connection errors out.

This method takes no parameters.

This method doesn't return anything.

postHandshake(): void

This method is called by the CompositeBSClient after it has shaken hands with the BotSocket server.

This method is called after handshaking is done with the BotSocket server, making it safe to send messages (event, query or otherwise) to the server in this method.

This method takes no parameters.

This method doesn't return anything.

supplementClientHandshake(clientHandshake: BotSocket.Protocol.Messages.ClientHandshakeData): BotSocket.Protocol.Messages.ClientHandshakeData

This method is for supplementing the data that's going to be sent as part of a BotSocket ClientHandshake.

The clientHandshake: BotSocket.Protocol.Messages.ClientHandshakeData parameter contains the original handshake data that will be sent to the server.

This method returns the modified data to be sent to the server.

Leafs can get the value returned by the last leaf in the branch via the arguments variable, like so:

const lastResult = arguments[arguments.length - 1];

supplementStaMPQuery(query: StaMP.Protocol.QueryMessage): StaMP.Protocol.QueryMessage

This method is for supplementing a StaMP query message that's going to be sent to the BotSocket server.

The query: StaMP.Protocol.QueryMessage parameter contains the original StaMP query message that will be sent to the server.

This method returns a new modified query message object, based on the original & previous query message objects.

Leafs can get the value returned by the last leaf in the branch via the arguments variable, like so:

const lastResult = arguments[arguments.length - 1];

Keep in mind that StaMP query messages have a data field of type object, and that Object.assign doesn't merge child object properties. If you implement this method, you must make sure to merge the data the field as well. See AbstractUserIdLeaf for an example of this.

supplementStaMPEvent(event: StaMP.Protocol.EventMessage): StaMP.Protocol.EventMessage

This method is for supplementing a StaMP event message that's going to be sent to the BotSocket server.

The event: StaMP.Protocol.EventMessage parameter contains the original StaMP event message that will be sent to the server.

This method returns a new modified event message object, based on the original & previous event message objects.

Leafs can get the value returned by the last leaf in the branch via the arguments variable, like so:

const lastResult = arguments[arguments.length - 1];

Keep in mind that StaMP event messages have a data field of type object, and that Object.assign doesn't merge child object properties. If you implement this method, you must make sure to merge the data the field as well. See AbstractUserIdLeaf for an example of this.

This also applies to any modifications being made to the payload field of event messages, which is also of type object.

processServerHandshake(serverHandshake: BotSocket.Protocol.Messages.ServerHandshakeData): void

This method is for processing the data returned by the BotSocket server as part of its handshaking.

The serverHandshake: BotSocket.Protocol.Messages.ServerHandshakeData parameter contains the data passed by the server.

processRenderLetterRequest(renderLetterData: BotSocket.Protocol.Messages.RenderLetterData): void

This method is for processing the data passed by the server in a render-letter request.

The renderLetterData: BotSocket.Protocol.Messages.RenderLetterData parameter contains the data passed by the server.

Leafs included in this starter pack

Here is a brief overview of the leafs included in this package:

Class name	Usage
AbstractRendererLeaf	Abstract leaf that handles rendering messages as and when required during the usual operations of a CompositeBSClient.
DebugRendererLeaf	Renderer leaf that 'renders' all messages to the console via debug.
AbstractArchiverLeaf	Abstract leaf that handles persisting messages as and when required during the usual operations of a CompositeBSClient.
SessionStorageArchiverLeaf	Archiver leaf that handles persisting messages using the sessionStorage API.
AbstractLocationLeaf	Abstract leaf that handles managing & providing a location as and when required during the usual operations of a CompositeBSClient.
StaticLocationLeaf	Location-managing leaf that that simply uses a static lat & lng that can be changed with getters & setters.
BrowserLocationLeaf	Location-managing leaf that gets its location via the geolocation browser API.
AbstractTimezoneLeaf	Abstract leaf that handles managing & providing a timezone as and when required during the usual operations of a CompositeBSClient.
StaticTimezoneLeaf	Timezone-managing leaf that that simply uses a static timezone that can be changed with getters & setters.
AbstractUserIdLeaf	Abstract leaf that handles managing & providing a user as and when required during the usual operations of a CompositeBSClient.
CookieUserIdLeaf	UserId-managing leaf that persists a userId via a browser cookie.
SessionStorageUserIdLeaf	UserId-managing leaf that persists a userId using the sessionStorage API.
StaticUserIdLeaf	UserId-managing leaf that that simply uses a static userId that can be changed with getters & setters.
AutoReconnectLeaf	Leaf that handling automatic reconnects after a delay when the CompositeBSClient disconnects from the BotSocket server.
ScrollToBottomOnLetterLeaf	Leaf that scrolls to the bottom of an HTMLElement when a render-letter request arrives.
ScrollToPositionOnLetterLeaf	Leaf that scrolls to a position of an HTMLElement when a render-letter request arrives.
ScrollToTopOnLetterLeaf	Leaf that scrolls to the top of an HTMLElement when a render-letter request arrives.
EmitStatusMessageEventsLeaf	Leaf that emits status messages events based on the usual operations of a CompositeBSClient, via an EventEmitter.
EmitLetterMessageEventsLeaf	Leaf that emits letter messages events based on the usual operations of a CompositeBSClient, via an EventEmitter.
TalkingLeaf	Leaf that speaks StaMP messages (that have audio).
ToggleDisabledOnConnectLeaf	Leaf that toggles the disabled state of an HTMLElement when a CompositeBSClient connects and disconnects.
SendInputQueryOnFormSubmitLeaf	Leaf that sends the value of an HTMLInputElement when an HTMLFormElement is submitted.
SendEventOnHandshakeLeaf	Leaf that sends an event message to the server once handshaking is complete, triggering a bot response (if supported).
ConversationDataIncluderLeaf	Leaf that handles including conversation store & context in the data property of every message send by the CompositeBSClient.

Note that not all of the leafs use methods defined in BSClientLeaf. Leafs are also useful as way of grouping functionality related to the CompositeBSClient.

Identifying the user of a client

The userId in the BotSocket system is how users are identified and tracked. Each id represents a whole new user to Zwerm.

It has two primary uses in the BotSocket system:

• BotSocket clients use it as the senderId property in StaMP query messages, to indicate where the messages came from.
• BotSocket server uses it to group client connections, and to deliver messages sent via the API to the correct clients.

The BotSocket server provides connected clients with the userId to use, passed as part of the servers handshake request with the client.

A client can specific its own userId as part of the clients handshake request with the server. The server will take that userId into account when deciding which userId to provide the client with.

If the server accepts the userId provided by the client, it'll use that userId, otherwise it'll generate one for the client to use. More on this in the "Handshaking" section of "BotSocket 101".

The userId should be a string - if it's not, the server will typecast it to a string, and return the result back to the client. This is because Zwerm requires string ids, and will throw an error if an id is used that's not of type string.

By default, the CompositeBSClient will just accept whatever userId the server generates, with no form of persistence between sessions.

Control over the userId is done using leafs; for security and ease of use, we recommend using the AbstractUserIdLeaf.

This leaf contains all the implementation code required to properly control the userId, defining an abstract getter & setter for you to implement. By using this leaf, you only have to focus on ensuring the getter & setter returns the desired userId, and not how that value is actually used by the client.

BotSocket 101

BotSocket is a protocol that defines the structure implementers expect WebSocket messages to be in when communicating.

It also loosely defines 'best behaviour' of clients and servers, that is followed by Zwerms implementation of BotSocket.

A BotSocket message is made up of two parts: the request string property, and the data object property.

The request property is a string whose defined value denotes the structure to expect of the data property, as well as how that data should be used.

Currently, the following request types are defined:

• handshake, denoting that data will match either ClientHandshakeData or ServerHandshakeData, depending on if it was a BotSocket client or server that sent the message.
• submit-query, denoting that data will match SubmitQueryData, which in turn defines it'll match StaMP.Protocol.Messages.StandardisedQueryMessage.
• render-letter, denoting that data will match RenderLetterData, which defines an interface with a letter property, of type StaMP.Protocol.Letter.

Handshaking

When a BotSocket client connects to a BotSocket server, it's expected that the client will send a handshake request, containing information for the server about the client. The server will then send a handshake request back, containing information for the client about the server, such as confirmation data.

Client handshake

A handshake request from a client will have the RequestType of handshake, and its data structure, as defined by ClientHandshakeData, will have the following properties:

(optional properties are marked with a question mark '?')

• userId: required, the id of the user that the connected client is messaging on behalf of. This is used by the server to utilise user-specific information, and track the user through the Zwerm ecosystem.
• timezone?: optional, the timezone that the connected client is currently in.

Leafs can supplement a client handshake with the supplementClientHandshake method.

Server handshake

A handshake request from the server will have the RequestType of handshake, and its data structure, as defined by ServerHandshakeData, will have the following properties:

(optional properties are marked with a question mark '?')

• userId: required string; the id of the user that the connected client is considered to be representing by the server.
• retryWaitTime: required number; the number of seconds that the connected client should wait before trying to reconnect to the server, in the event of a disconnection

Note that if the userId property doesn't match the one sent by the client in its handshake, it means the server rejected that id for whatever reason.

This should be dealt with accordingly by the client, as it means that anything the client does will be considered by the server to be on behalf of the user the server considers the client to be representing, regardless of what the client says or thinks. It's rare for a server to reject a client-provided user id.

Leafs can utilise the data sent by the servers handshake (such as to set a field) with the processServerHandshake method.

Sending user queries

To submit a message from the user to the BotSocket server, you send a request of type submit-query, with the data property being a StaMP query message.

This can be done by calling the CompositeBSClient#sendQuery method.

Leafs can supplement a query being sent (such as to add timezone or location data) with the supplementStaMPQuery method.

Sending client events

To submit an event from the client to the BotSocket server, you send a request of type submit-event, with the data property being a StaMP event message.

This can be done by calling the CompositeBSClient#sendEvent method.

Leafs can supplement a event being sent (such as to add timezone or location data) with the supplementStaMPEvent method.

Rendering letters

When the server wants a client to deliver something to the user (such as some text or that the server or bot is 'thinking'), it'll send a render-letter request.

A render-letter request will have the RequestType of render-letter, and its data structure, as defined by RenderLetterData, will have the following properties:

(optional properties are marked with a question mark '?')

• letter: required StaMP letter; A StaMP letter containing StaMP messages to be rendered (whatever that might entail).

CompositeBSClient itself does nothing towards the rendering of StaMP letters. This functionality is implemented in leafs.

Leafs can process received render-letter requests with the processRenderLetterRequest method.