Heroku based app written in coffeescript interacting with Xero Reports API

I have some existing node.js coffeescripts that are hosted on Heroku that connect to Xero and Slack as a private app. I want to change this to be a public app so that as a Slack App it can authenticate on Xero and connect, or as a Xero app can auth on Slack for anybody. This will need changes to the coffeescript to do the Oauth handling right and I am currently muddling through this but would like someone who has been there and done it to save me some time and point out errors/fixes.