this post was originally written on 2016/10/11 for my personal blog on hawkins.is

If you're like me, you love @everyone in Slack, and your group desperately needs that feature.

Maybe there are free cookies on the Quad on campus; you've gotta tell your friends! Why can't you just say "@all of you get out to the quad for free cookies!"?!

After following along with this blog, you can!

How it works

We'll be writing a Hubot script using the hubot-groupme adapter to deploy on Heroku that will listen for messages with "@all" in them in a given GroupMe room. We'll deploy our bot for free* on Heroku.

Free for the first 550 (or 1000 if you verify a credit card) hours per month

Then, we can tag everyone in the group (minus a blacklist) by saying anything with "@all" in the message.

Note: You can host the bot on your own server instead, but I'm writing this for anyone to be able to handle. If you know how to host bots / scripts on your own machine, you shouldn't have any trouble translating the few Heroku-specific instructions. Moving on...

How it works (technical)

If you're the type of guy that throws the manuals away when you buy a product, scroll past this section.

Hubot uses regular expressions to match messages in a chat room. Groupme-at-all listens for /.*@all.*/i to act. It will construct a message to send in an HTTP POST request to the GroupMe v3 API.

Note: GroupMe's API is not well-documented. Multiple features are completely or partially ignored. In fact, mentions are not documented at all! So tagging, as far as I can determine, is handled similarly to an image or emoji attachment, which maps a User ID to a string of characters, which appear as bold text to users.

So after receiving the command, the bot maps every user's ID to an individual character in the message for a tag, since some GroupMe versions seem to require a tag of length >= 1.

Next, the bot stringify's the message object and sends the HTTP POST request, logging the results.

Check out the actual code used to do all this:

robot.hear /(.*)@all(.*)/i, (res) ->
  """@all command"""
  text = res.match[0]
  users = robot.brain.users()
  if text.length < users.length
    text = "Please check the GroupMe, everyone."
  message =
    'text': text,
    'bot_id': bot_id,
    'attachments': [
      "loci": [],
      "type": "mentions",
      "user_ids": []
    ]
  i = 0
  for user, values of users
    if user in blacklist
      continue
    message.attachments[0].loci.push([i, i+1])
    message.attachments[0].user_ids.push(user)
    i += 1
  json = JSON.stringify(message)
  options =
    agent: false
    host: "api.groupme.com"
    path: "/v3/bots/post"
    port: 443
    method: "POST"
    headers:
      'Content-Length': json.length
      'Content-Type': 'application/json'
      'X-Access-Token': token
  req = https.request options, (response) ->
    data = ''
    response.on 'data', (chunk) -> data += chunk
    response.on 'end', ->
      console.log "[GROUPME RESPONSE] #{response.statusCode} #{data}"
  req.end(json)

How to install groupme-at-all

Installing this is easy, but there's a few steps...

Create a GroupMe Bot

GroupMe has native bot integration - they're kind of just an API token for your scripts to use, but that's all Hubot needs.

1. Navigate to the GroupMe dev site and log in with your GroupMe account
2. Click create a new bot
3. Choose the group your bot will live in
4. Name your bot (something like "All" will do)
5. Provide a callback URL (doesn't really matter for us, but has to be unique)
6. Provide a URL for an image for your bot to use (my favorite is All brand laundry detergent)
7. Click submit

Now you'll be lead to a page with your GroupMe bot's ID, ROOM_ID, and TOKEN. Copy these guys into a note, you'll need them again in a moment.

Setup Hubot

Follow the instructions at Hubot Getting Started to install and wrap your head around Hubot. Just remember to use the adapter groupme.

It's easy, so just get the general idea after you install it.

Setup @all

Now you're ready for the fun stuff! I've already written the code for you, so all you need to do is...

1. Fork my groupme-at-all repository to your own GitHub account. (Bonus points if you "Star" it ;) )
2. Log in (or create an account) to Heroku
3. Create a new app on Heroku
4. Choose to deploy from your GitHub and select the repo
5. Configure environment variables (see below)

Configure Environment Variables

Hubot is centered around environment variables for accessing sensitive information.

1. Load your app's settings and click "Reveal Config Vars"
2. Add the config variables and the appropriate values from your GroupMe Bot you made earlier:
   • HUBOT_GROUPME_BOT_ID
   • HUBOT_GROUPME_ROOM_ID
   • HUBOT_GROUPME_TOKEN

Test Your Bot

At this point, you should be good to go!

To start the bot, start your Heroku app (or run ./bin/hubot -a groupme from your repo's root directory if you're not using Heroku).

Give it a moment to start up, and then use your regular GroupMe account (phone, desktop, etc) to say "Testing @all!" in your group. You should see your bot reply "Testing @all" in bold text since it tagged everyone in your group!

Success!

Hooray!! You can finally tell EVERYONE about Free Chips & Queso day at Moe's!

Your bot's good to go now, but there's some optional configuration you may prefer to do still, such as keep your bot awake.

(Optional) Further Config

Here's what else the bot can do:

• Set up a ping bot to keep your Heroku instance alive
• Handle a blacklist to not mention specific users by ID

Begone, sleep!

Speaking of writing blog posts at 2am... your bot would love to be an insomniac. Otherwise, he'll fall asleep after only an hour only to be awoken manually later. So, if you're using Heroku, you've got a few options...

1. Pay Heroku for a better plan. If you plan to do some serious work here, I'd suggest this. If it's just for your Sunday Brunch club, maybe not.
2. Or set up a ping site like Pingdom or Uptime Robot to hit your Heroku App's URL periodically. This is the easiest option if you don't want to code anything.
3. Or set up heroku-keep-alive. I've had some issues with this one, but some people like it!
4. Or finally make a simple setInterval in your app. Something as easy as var http = require("http"); setInterval(() => (http.get("http://your-app-name-goes-here.herokuapp.com"), 300000)); to ping your Heroku app every 5 minutes will do.

Remember, if you're on a free Heroku plan, you're limited to 550 free hours, or 1000 if you verify a credit card. If you host this bad boy on your bot already should be a fully-functioning insomniac. Congrats!

Blacklist

Groupme-at-all uses a redis server controlled by Hubot to keep a persistent blacklist. This can be a tricky to get set up, so I'll leave this mostly as an excercise for you to understand.

In a nutshell tho, here's what you'll do...

1. Create a redis server
2. Configure hubot to use this server
3. Say "blacklist @so-and-so" to blacklist "so-and-so" in GroupMe
4. Cry that people don't want to be notified about free food trucks outside the office

But, you don't exactly need a redis server. The only issue is, that without it, your blacklist will reset every time your bot sleeps. That's pretty useless, but if your bot never sleeps then spend this time writing your own post on how computers are everything a college student ever dreamed of being in finals week.