token.js

const rp = require('request-promise')
const config = require('./lib/config')
const netlifyUrl = require('./lib/netlifyUrl')
const redirect = require('./lib/redirect')

const {
  clientId,
  devClientId,
  clientSecret,
  devClientSecret,
  apiPath,
  appPath
} = config

exports.handler = async (event, context) => {
  const { error, code } = event.queryStringParameters
  const { siteUrl, production } = netlifyUrl(event, context)

  if (error) {
    return { statusCode: 403, body: 'Error' }
  }

  const access = await rp({
    uri: 'https://slack.com/api/oauth.access',
    json: true,
    qs: {
      code,
      client_id: production ? clientId : devClientId,
      client_secret: production ? clientSecret : devClientSecret,
      redirect_uri: `${siteUrl}${apiPath}/token`
    }
  })

  if (access.error || !access.ok) {
    return {
      statusCode: 403,
      body: access.error || 'Not ok'
    }
  }

  return redirect(
    `${siteUrl}${appPath}${
      // This makes it easier to test that we are redirecting with the proper
      // information since we cant access the url hash from the request. This
      // is a good thing as far as the app is concerned, but makes it impossible to test/
      process.env.NODE_ENV === 'test' ? '?query=' : '#'
    }${encodeURIComponent(JSON.stringify(access))}`
  )
}