slack-calc-bot

Bot for Slack that evaluates arithmetic expressions. Supports addition (+), subtraction (-), multiplication (*, ×), division (\, ÷), exponentiation (^) (use exponentiation for square roots & other roots) & parenthesis ((, )).

Setup

These steps jump between local machine, Slack side & fly.io a lot, so please bear with me.

On your machine

• Install Ruby.
• Install Bundler - gem install bundler
• Clone this repo
• (Optional) If you'd like to host the bot on fly.io
  • Install flyctl (instructions here).
  • Auth flyctl
  • From the repo directory, run flyctl apps create & choose options as prompted.
  • Note down the the app name you chose here, referred to as <FLY-IO-APP-NAME>.
  • Fill in this name <FLY-IO-APP-NAME> in fly.toml where it says <FLY-IO-APP-NAME>.
  • Go to https://fly.io/apps/<FLY-IO-APP-NAME> & note down it's hostname, will be referred to as <FLY-IO-APP-URL>.

On Slack side

• Create a new application at https://api.slack.com/apps using the template manifest @ slack-manifest.yml filling in the following details:
  • <URL-TO-YOUR-APP>: can be either ngrok URL for development or <FLY-IO-APP-URL> if you're hosting on fly.io.
• Note down the 'Signing Secret' given on the 'Basic Information' page for the application (should be of form https://api.slack.com/apps/<some-app-id>/general?)
• Install application to your workspace & note down the Bot User OAuth Token on the 'Install App' page for the app (should be of form https://api.slack.com/apps/<some-app-id>/install-on-team?)

Back on your machine (for local development)

• From the repo directory, run bundle install
• Set two environment variables as follows from the Slack information we noted down earlier:
  • SLACK_SIGNING_SECRET=<Signing Secret noted down from the 'Basic Information' page on Slack>
  • SLACK_BOT_ACCESS_TOKEN=<Bot User OAuth Token noted down from the 'Install App' page on Slack>
• Run the Rails application via bundle exec rails server

Back on your machine (for fly.io deployment)

• Run flyctl secrets set SLACK_SIGNING_SECRET=<Signing Secret noted down from the 'Basic Information' page on Slack>
• Run flyctl secrets set SLACK_BOT_ACCESS_TOKEN=<Bot User OAuth Token noted down from the 'Install App' page on Slack>
• Run bundle exec rails secret & copy the value that's printed.
• Run flyctl secrets set SECRET_KEY_BASE=<value copied in last step>
• Run flyctl deploy to deploy
• You should see that fly.io successfully deploys your bot

Back on Slack

• Navigate to the 'App Manfiest' page for your app (should be of form https://app.slack.com/app-settings/<some-id>/<some-id>/app-manifest)
• You'll see a message at the top regarding your request URL not being verified, go ahead and verify the URL. As long as you did the previous block properly on your machine/server, the verification should be successful.

You're all set to start messaging the app/bot. Invite the bot to your channel & highlight it with arithmetic expressions. Direct messages to the application also work.

Tests

This assumes you've completed the On your machine & Back on your machine (for local development) section above. To execute tests run bundle exec rspec.

Main source code locations

• Slack::EventsController - implements endpoint for Events API app/controllers/slack
• Slack::WebApi - Wrapper to call Slack WebAPI lib/slack
• InfixEvaluator - Class to parse and evaluate infix arithmetic lib
• Slack::CalculateAndSendJob - Async job to do infix evaluation & sending of slack message app/jobs/slack
• Test specs - RSpec tests spec