Facebook Messenger Chat Kit

An event driven SDK for Facebook Messenger chat bots.

FBM is a full-featured, opinionated Facebook Messenger SDK for writing bots. In addition to wrappers around the Messenger API, you get:

• A session store for storing state between messages
• Auto-populated profile information so you can address by name from anywhere
• Listeners for greetings and help text to follow best practices
• Easy to add metrics to your bot
• Support for deployment on multiple pages

Usage

const { Messenger } = require('launch-vehicle-fbm');
const messenger = new Messenger(options);
messenger.start();  // Start listening

Options

• cache (default: cacheman memory cache) See Session cache
• hookPath (default: /webhook)
• pages: A map of page ids to page access tokens {1029384756: 'ThatsAReallyLongStringYouGotThere'}. Currently optional but config will migrate to this in the future
• port (default: 3000)
• emitGreetings (default: true) When enabled, emits common greetings as text.greeting events. When disabled, no check is run and text events will be emitted. Optionally, can be set to a RexExp object which will enable the option and use the specified expression instead of the built-in default.

Additional options are set via environment variables. See example.env for an example.

Endpoints

• /webhook (override with options.hookPath) -- The Messenger webbhook
• /pause -- Dashbot compatible pause for live person takeovers. See Dashbot's docs for usage. Currently, pauses only last for 12 hours in case the operator forgets to unpause

Responding to events

We emit a variety of events. Attach listeners like:

// General form
// messenger.on(eventName, ({dataItem1, dataItem2}) => {});
const { Messenger, Text, Image } = require('launch-vehicle-fbm');
const messenger = new Messenger();
messenger.on('text', ({reply, text}) => {
  if (text.includes('corgis')) {
    reply(new Text('aRf aRf!'))
      .then(() => reply(new Image('https://i.imgur.com/izwcQLS.jpg')));
  }
});
messenger.start();

Event data

All events contain the following attributes in the data:

• event The raw event
• reply: Function Reply back to the user with the arguments
• senderId The ID of the sender
• session A Session object you can mutate

In addition, data contains these attributes on specific events:

• text Text message
  • source One of quickReply, postback, text
  • text Original message content: event.message.text for text events and payload for postback and quickReply events
  • normalizedText Normalized message content
• text.greeting (optional, defaults to enabled) Text messages that match common greetings
  • firstName Trimmed first name from the user's public Facebook profile
  • fullName Concatenating of firstName and surName with a single, separating space
  • surName Trimmed first name from the user's public Facebook profile
• text.help (optional, defaults to enabled) Text messages that match requests for assistance
  • no additional attributes provided
• message Any kind of message event. This is sent in addition to the events for specific message types.
  • message Direct access to event.message
• message.image Image (both attached and from user's camera)
  • url Direct access to event.message.attachments[0].payload.url for the url of the image
• message.quickReply For conversation, use the text event, this is for the raw message sent via a quick reply button
  • payload Quick reply content, event.quick_reply.payload
• message.thumbsup User clicked the "thumbsup"/"like" button
  • no additional attributes provided
• message.sticker Sticker
  • no additional attributes provided
• message.text For conversation, use the text event
  • text Message content: event.message.text
• message.quickReply For conversation, use the text event, this is for the raw message sent via a quick reply button
  • payload Quick reply content: event.quick_reply.payload
• postback For conversation, use the text event, this is for the raw message sent via a postback
  • payload Postback content: event.postback.payload
• referral Fires when a user scans your Messenger code
  • referral Referral content (from Facebook):
    • referral.ref A custom ref for a parametric code
    • referral.source MESSENGER_CODE
    • referral.type OPEN_THREAD

Other Events

• app.starting signal that the Messenger.start has been called and the application is in the process of coming online

• app.started signal that the SDK's Express server is now listening on the specified port and ready for requests

• finish (optional) Signal that you're done processing. This is mostly useful for your tests when you have Promise chains. The SDK currently does nothing with this event.

Normalized message content

To help keep application code simple, the SDK makes these guarantees about normalized text:

• it will be lowercase
• it will be stripped of leading and trailing whitespace

A special note about echo events

If you enable message_echoes in your Messenger webhooks, you'll get bot messages too. You'll need to examine event.message.is_echo in your handlers.

The session object

The SDK uses cacheman to maintain session data per user. The session object is passed through each event and can be read from or written to as needed. While the session is automatically saved in routeEachMessage, there are instances where it may be advantageous to manually trigger a save; this can be accomplished by using messenger.saveSession. The session object has a copy of its own session key (pro tip: do not modify or remove _key) so the session object is the only parameter that needs to be passed into saveSession.

The SDK sets some values in the session:

• count: int how many events have been received from this user
• lastSeen: int The time (in milliseconds since epoch time) we last saw activity
• profile: Object, the profile as retrieved from Facebook Messenger. See the docs for the most up to date information. If a profile can't be pulled, it's {}, otherwise, here are some of the more useful fields for quick reference:
  • profile.first_name: first name
  • profile.last_name: last name
  • profile.profile_pic: profile picture
• source: string|undefined A guess of where the user came from for this session:
  • direct TODO, not implemented yet
  • return A returning visitor
  • web Came from a "Send to Messenger" button on a website
  • undefined Unknown

Session cache

If you want to customize the cache, you can supply your own cache in the Messenger constructor. By default, it uses the cacheman memory cache, but any cache that follows these simple patterns will work:

• cache.get(key: string): ?Promise<Object>
• cache.set(key: string, value: Object): Promise<Object>

We strongly suggest using something like Redis that will persist across restarts. There are examples in the wiki.

Other APIs

• require('launch-vehicle-fbm').SESSION_TIMEOUT_MS: This constant is available if you need some sort of magic number for what to consider a session length
• Messenger.app: The base Express app is available for you here

Logging and metrics

1. debug is for a firehose of data sent to stdout/stderr
2. dashbot is a service we're trying that gives us analytics tailored for bots.
3. winston is like dashbot and a subset of debug, but it's designed specifically to let us recreate/monitor conversations.

Optional environment variables:

• DASHBOT_KEY - If this is present, dashbot integration will be on

• LOG_FILE – winston will log conversations to this file. It should be an absolute path

• SLACK_CHANNEL - The Slack channel winston should use, can be a name or an id

• SLACK_WEBHOOK_URL – The webhook url is required for winston to send to Slack

Prior art

There are many other Messenger Node packages; we made a page to help you decide if this is the appropriate one for your project: https://github.com/CondeNast/launch-vehicle-fbm/wiki/Prior-art