Slack: Send Later

A Slack app that enables you and your team to schedule your messages, and to never bother your teammates in their free time while still not forgetting important stuff!

Contributions

After following this setup, the installed Slack Bot will listen to the following commands:

/later <message> (at|in) <time> in order to create a new scheduled message
- Examples:
  - /later Hey @john.doe! Are you free today? Need your help. at next Monday 9am
  - /later I got an issue, are you free? in 1 hour
/later list to list all your scheduled messages in a channel
/later help prints a help message to inform you about the different commands
/later examples prints out some examples on how to schedule messages

Of course, after scheduling a message, you will get a confirmation with the message text and the scheduled timestamp. Also, you'll get the opportunity to cancel your scheduled message.

Same goes for listing all scheduled messages.

Install the Slack App for Your Workspace

This application is the corresponding server for your Slack App which will listen to incoming events.

Setup the Slack App

Create a Slack App

Go to the Slack Web API and login with your Slack account.
Click Create new App and select a name and the workspace you're developing the app for.
Scrolling down the page, find the Display Information section and fill in a name, a short description and a logo for your app, and hit Save Changes.

Deploy this Express application

Last, you need to deploy this application. You will have to set the environment variables that are listed in .env.example accordingly.

In the Slack Web API, select your app's Basic Information and scroll down to App Credentials. Copy your Slack app's Client ID, Client Secret, and Signing Secret and paste them into the ENV variables SLACK_CLIENT_ID, SLACK_CLIENT_SECRET, and SLACK_SIGNING_SECRET.

(Don't forget the BASE_URL which has to equal your domain you used when configuring the Slack App.)

Setup Permissions

To setup the permissions, go to Features > OAuth & Permissions
In the first section of the page, click on Add New Redirect URL,
enter https://nice-domain.com/slack/oauth_redirect (of course by using your domain),
and hit Save URLs
Scroll down a bit to Scopes and add the following scopes:
- Bot Token Scopes
  - channels:read
  - chat:write
  - commands
  - users:read
- User Token Scopes
  - channels:read
  - chat:write
  - groups:read
  - im:read
  - mpim:read

Setup your App's Home

Now, go to Features > App Home and activate App Home.
Then, scroll down to Show Tabs and activate both ticks for Home Tab and Message Tab

Setup Interactivity

Then, go to Features > Interactivity & Shortcuts and activate the toggle
In the text field Request URL, enter the domain of the server application
suffixed by the path /slack/events, i.e., https://nice-domain.com/slack/events
Next, go to Features > Slash Commands and hit Create New Command

Set it up as specified in the image (or to your liking),
but remember to set your Request URL to https://nice-domain.com/slack/events
and to tick Escape channels, users, and links sent to your app
Hit Save Changes

Setup Events

Then, go to Features > Event Subscriptions and activate the toggle Enable Events
As above, set the Request URL to https://nice-domain.com/slack/events
Click on the accordion Subscribe to bot events and add the following events:
- app_home_opened
- tokens_revoked
Hit Save Changes and you've completed the first half!

Development Setup

In case, you want to test the app or add further functionalities, follow this setup.

Prerequisites

node >= 12.6
a running postgres instance.
An ngrok account with the ngrok CLI
A Slack account and a Slack workspace (you can use to develop and test)

Setup

Install dependencies: yarn install
Create a Slack App, but leave the links out
Setup ENV variables
- run cp .env.example .env
- refine your database ENV variables if you like
- copy your Slack app's Client ID, Client Secret, and Signing Secret
  and paste them into the ENV variables SLACK_CLIENT_ID, SLACK_CLIENT_SECRET,
  and SLACK_SIGNING_SECRET
- Choose or generate a secret and paste its value into the variable STATE_SECRET
  (It can be literally anything)
Setup your database
- create your database with npx sequelize-cli db:create
- run database migrations with npx sequelize-cli db:migrate
Run server with yarn start
Create a tunnel to your localhost with ngrok http 3000 (or the respective port you chose)
When setting up your Request URLs in the step Create a Slack App,
you have to setup the same paths, except you will be using the hostname of your ngrok tunnel (preferably, the HTTPS one)
Open the URL https://<YOUR NGROK HOSTNAME GOES HERE>.ngrok.io/slack/install
and click on the Add to Slack button.
Follow the OAuth flow to install the app to your test workspace
Now, the user that added the Slack App has automatically authorized the app.
Other users will have to authorize when running their first /later-command
Happy coding!

Remarks

TailwindCSS is used within this application in a very minimalistic version.

Hence, if you want to utilize this framework and adapt some views, you will have to run
npx tailwindcss-cli@latest build -o public/assets/tailwind.css in order to utilize all utility classes.

If you want to deploy your modified version, you will have to run first
NODE_ENV=production npx tailwindcss-cli@latest build public/assets/tailwind.css -o public/assets/tailwind.css to minify your tailwind stylesheet.

zweitag/slack-send-later