resolver-middleware-pattern.js

import { compose } from 'redux'

const ensureLoggedIn = (next) => (obj, args, ctx) => {
  if (!ctx.user) {
    throw new Error('Not authorized')
  }
  return next(obj, args, ctx)
}

const intersection = (array1, array2) => array1.filter((n) => array2.includes(n))

const ensureScopes = scopes => next => (obj, args, ctx) => {
  if (!intersection(scopes, ctx.user.scopes).length) {
    throw new Error('Forbidden')
  }
  return next(obj, args, ctx)
}


const logArgs = (cb) => (obj, args, ctx) => {
  console.log(args.arg1)
  return cb(obj, args, ctx)
}

const resolver = (obj, args, ctx) => {
  return obj.name
}

const enhancedResolver = compose(
  ensureLoggedIn,
  logArgs,
  ensureScopes(['admin', 'subadmin']),
)(resolver)

const params1 = [{name: 'Rafael'},{arg1: 'Log me1'},{user:{scopes:['admin']}}]
const params2 = [{name: 'Rafael'}, {arg1: 'Log me2'}, {}]
const params3 = [{name: 'Rafael'}, {arg1: 'Log me3'}, {user: {scopes: ['noob']}}]
  
try {
	console.log('Test 1 - should print Log me1 and Rafael')
	console.log(enhancedResolver(...params1))	
}
catch (err) {
	console.log(err.message)
}
console.log('------------------------')

try {
	console.log('Test 2 - should throw Not authorized')
	console.log(enhancedResolver(...params2))	
}
catch (err) {
	console.log(err.message)
}
console.log('------------------------')

try {
	console.log('Test 3 - should print Log me3 and throw Forbidden')
	console.log(enhancedResolver(...params3))
}
catch (err) {
	console.log(err.message)
}
console.log('------------------------')