You’ll need to create a Slack app (not a classic one) with at least the following bot token scopes. The reasons each scope is required are also included:
-`channels:history` (or `groups:history`, if it’s a private channel): Used to listen to messages sent.
-`chat:write`: Used for sending messages.
-`reactions:write`: For reacting to invalid messages.
Then you’ll need to subscribe the app to a few events. The server has an endpoint open at `/slack/events`, so when you’re asked for a request URL, just put `https://<SERVER>/slack/events`. Only the following events are needed:
-`message.channels` (or `message.groups` if it’s a private channel)
### Environment variables
Here are all the variables you need to set up, with hints.
```bash
# The port to run the app server on
PORT=3000
# Redis database to store the last number and its sender
REDIS_URL=redis://…
# App config. Obtained from the "Basic Information" page of your app.