Your StdLib Slack App

Welcome to your StdLib Slack template!

If you're not sure what StdLib ("Standard Library") is, please check out https://stdlib.com.

Here we'll walk you through how StdLib works, your Slack App endpoints, and how to handle Slack Slash Commands, Events, and Actions from interactive messages.

Your Project

The first thing you'll probably notice is your functions/ directory. This is your StdLib function directory which maps directly to HTTP endpoints. There are five main functions in your Slack App:

• __main__.js
• auth.js
• commands/__main__.js
• events/__main__.js
• actions/__main__.js

We'll go through these in the order listed here.

Function: functions/__main__.js

This is your main endpoint, corresponding to https://username.lib.id/service/. This is, of course, where username is your username and service is your service name.

Any time a function has the filename __main__.js, the enclosing folder is used as the route name over HTTP. You can think of it like the default function for a specific directory.

Note that when pushing to a development environment (or if you want to access a specific version), this should be reached via: https://username.lib.id/service@dev/main (if your dev environment is called dev, also the default local environment name) or https://username.lib.id/service@0.0.0/main (if your version is 0.0.0).

Usage

This endpoint generates a template based on the contents of pages/index.ejs, which is modifiable and contains your "Add to Slack" button. It is the easiest way to distribute your app to other users.

Function: functions/auth.js

This is the OAuth endpoint for your Slack App that verifies another team (or your own) has properly validated the slack app.

Usage

This endpoint processes an OAuth request and returns the contents of slack/pages/auth.ejs. (Typically "Success!" if successful.)

Function: functions/commands/__main__.js

This is the main Command Handler function for handling Slack Slash Commands. You can read more about them here: https://api.slack.com/slash-commands

This function is triggered by slack at the following URL: https://<username>.lib.id/<service>@<ver>/commands/:bg

Where <username> is your username, <service> is the service name and <ver> is the environment or semver release of your service. The :bg indicates you'd like this function to return an HTTP 2XX code as quickly as possible and do all processing behind the scenes. (Ideal for Slack.)

Usage

To add or modify Slash commands, you'll want to look in the directory functions/commands/ and create files with the name functions/commands/NAME.js where NAME is your intended command, and also add them to your Slash Commands list via Slack's Slash Command interface.

For the default "hello" command (should be added as /hello to your app) you'll notice the following boilerplate code:

module.exports = (user, channel, text = '', command = {}, botToken = null, callback) => {

  callback(null, {
    response_type: 'in_channel',
    text: `Hello, <@${user}>...\nYou said: ${text}`
  });

};

In this function, user and channel are strings representing the user and channel the command was called from. The contents of the command (text) are available in text, a full command object is available that contains all data passed from slack (https://api.slack.com/slash-commands), and a botToken for your Slack App's bot is passed in (if you want to use it to post additional messages, upload files, etc.).

The first parameter passed to callback is an error (if present), use new Error() when possible. The second parameter is a chat.postMessage object, more details can be found here: https://api.slack.com/methods/chat.postMessage.

You can test the sample hello command on the command line by running

$ lib .commands.hello test_user general "some text"

Function: functions/events/__main__.js

This is the main Event Handler function for handling public channel events from Slack's Event API: https://api.slack.com/events

This function is triggered by slack at the following URL: https://<username>.lib.id/<service>@<ver>/events/:bg

Where <username> is your username, <service> is the service name and <ver> is the environment or semver release of your service. The :bg indicates you'd like this function to return an HTTP 2XX code as quickly as possible.

You'll notice an * @bg params line in the comments for this function. This means, when executed as a background function, it will return a JSON object mapping to the parameters passed to it (which also passes Slack's challenge litmus test).

Usage

This function will delegate incoming events to their appropriate handler, which can be placed in functions/events/TYPE.js or functions/events/TYPE/__main__.js as these are functionally equivalent. If there is a subtype involved, functions/events/TYPE/SUBTYPE.js or functions/events/TYPE/SUBTYPE/__main__.js will be invoked.

By default your functions/events/message/__main__.js should look like this:

module.exports = (user, channel, text = '', event = {}, botToken = null, callback) => {

  // Only send a response to certain messages
  if (text.match(/hey|hello|hi|sup/i)) {
    callback(null, {
      text: `Hey there! <@${user}> said ${text}`
    });
  } else {
    callback(null, {});
  }

};

In this function, user and channel are strings representing the user and channel the event was triggered by. The contents of the command (text) are available in text, a full event object is available that contains all data passed from slack (https://api.slack.com/events), and a botToken for your Slack App's bot is passed in (if you want to use it to post additional messages, upload files, etc.).

The first parameter passed to callback is an error (if present), use new Error() when possible. The second parameter is a chat.postMessage object, more details can be found here: https://api.slack.com/methods/chat.postMessage.

You can test the sample message event on the command line by running:

$ lib .events.message test_user general "hello"

Function: functions/actions/__main__.js

This is the main Action Handler function for handling Slack Actions from interactive messages. You can read more about actions and interactive messages here: https://api.slack.com/docs/message-buttons.

This function is triggered by slack at the following URL: https://<username>.lib.id/<service>@<ver>/actions/:bg. You should add this URL to the interactive messages section of your Slack app dashboard.

Where <username> is your username, <service> is the service name and <ver> is the environment or semver release of your service. The :bg indicates you'd like this function to return an HTTP 2XX code as quickly as possible.

Usage

This function will delegate incoming actions to their appropriate handler, which should be placed in functions/actions/NAME.js.

We've included a simple sample handler for an action named example. The code for this is below:

module.exports = (user, channel, action = {}, botToken = null, callback) => {

  callback(null, {
    text: `Hello, <@${user}>!\nThis text will overwrite the original interactive message`,
    attachments: [{
      text: 'Try hitting this endpoint again by clicking the button!',
      fallback: 'Can\'t display attachment',
      callback_id: 'callback_id',
      actions: [
        {
          name: 'example',
          text: 'Refresh',
          type: 'button',
          value: 'value'
        }
      ]
    }]
  });

};

In this function, user and channel are again strings representing the user and channel the event was triggered by. A full action object is available that contains all data passed from Slack (https://api.slack.com/docs/interactive-message-field-guide#action_payload), and a botToken for your Slack App's bot is passed in (if you want to use it to post additional messages, upload files, etc.).

The first parameter passed to callback is an error (if present), use new Error() when possible. The second parameter is a chat.updateMessage object, more details can be found here: https://api.slack.com/methods/chat.update.

Whatever you choose to return in the second callback parameter will overwrite the original message. This parameter could be a confirmation message or another call to action. This value can be a simple string or an object that conforms to the spec set in chat.update (see https://api.slack.com/methods/chat.update. We automatically attach the token, ts, and channel params for you outside of this handler). You can also restore the original message in case of an error by returning Slack's original_message parameter, which will be present in the action parameter.

You could create a interactive message that would trigger this handler with the following Javascript code (you will have to run npm install slack --save first):

const slack = require('slack');

slack.chat.postMessage({
 token: process.env.BOT_TOKEN,
 channel: '#general',
 text: 'Respond to this',
 attachments: [{
   text: 'Here is the action:',
   actions: [
     {
       name: 'example',
       text: 'Press me',
       type: 'button'
     }
   ]
 }]
}, (err, result) => {
 // Handle result
});

You can retrieve your bot token from the OAuth and Permissions section of your Slack dashboard.

Additionally, you can test the example action locally from your command line by running:

lib .actions --action example --channel general --user user

Note: Your action handlers will only work with messages created via the slack.chat.postMessage API call.

Utilities

This Slack App template comes with some utility function in slack/utils. We'll go over a few of them;

• message.js
• update_message.js
• respond.js
• upload.js

Utility: utils/message.js

This function has a fingerprint of:

module.exports = (token, channel, text, callback) => {}

Where token is your bot token (the token used for the bot response), channel as the channel where the response is expected, text being a string or channel.postMessage object (for more granular control), and callback being a function expecting one parameter (an error, if applicable) that executes the call.

Use this function to get your bot to send messages to users or channels --- that's it. The token field should be passed in any slack/commands or slack/events handlers.

Utility: utils/update_message.js

This function has a fingerprint of:

module.exports = (token, channel, ts, message, callback) => {}

Where token is your bot token (the token used for the bot response), channel as the channel where the response is expected, ts as the timestamp of the message being updated, message being a string or chat.update object (for more granular control) that will replace the original message, and callback being a function expecting one parameter (an error, if applicable) that executes the call.

Use this function to get your bot to update messages in channels.

Utility: utils/respond.js

Very similar to message.js, this is a Slash Command response that HTTP POSTs a message to a webhook endpoint instead of creating a new bot message directly.

The benefits this has over message.js, is that Slash Commands can be used in private channels (or globally, within a team) where applicable.

Utility: utils/upload.js

Similar to message.js, this function has a fingerprint of:

module.exports = (token, channel, filename, contentType, file, callback) => {}

Where token is your bot token, channel is the channel to upload a file to, filename is the desired filename, contentType is the desired content type (i.e. a string like image/png), file is a Buffer of file contents and callback is a function that can handle an optional err parameter.

Helpers

There are a few helper functions for message formatting, etc. Feel free to look at them at your leisure, we've documented storage.js to better understand how team data is stored.

Helper: helpers/storage.js

This is a storage helper based upon https://stdlib.com/utils/storage. It is a basic key-value store that saves crucial team (including bot) details about each and every team its installed on, specific to the SLACK_APP_NAME field in your env.json and your StdLib (https://stdlib.com) account. You should probably avoid interfacing with this function directly, but it should be noted that it is critical for the ability to install your app on multiple teams.

That's it!

We hope this has served as a welcoming introduction to your Slack App project scaffold on StdLib --- happy building!

stdlib-slack-bot