// this is just here to display results to DOM
const addResultToDOM = (...args) => $('#root').append(`<div>${args.join(' ')}</div>`)

const compose = (...fns) => arg => fns.reduce((acc, fn) => fn(acc), arg)

const curry = (uncurriedFn, ...args) => {
  // you can get the arity of a function by calling length on the fn
  const arity = uncurriedFn.length 
  
  const accumulator = (...accArgs) => {
    let argsCopy = [...args] // 
    if (accArgs.length > 0) {
      argsCopy = [...argsCopy, ...accArgs]
    }

    if (args.length >= arity) return uncurriedFn.apply(null, argsCopy)
    return curry.apply(null, [uncurriedFn, ...argsCopy]) // recurse
  }
  // if any args passed in, pass them to the accumulator
  return args.length >= arity ? accumulator() : accumulator
}

const add = x => y => x + y
const subtract = x => y => y - x
const multiply = x => y => x * y
const divide = x => y => y / x
const sum = (x, y, z) => x + y + z

const [
  curriedAdd,
  curriedSubtract,
  curriedMultiply,
  curriedDivide,
  curriedSum
] = [
  add, 
  subtract,
  multiply,
  divide,
  sum
].map(i => curry(i)) // this simply creates curried versions of our functions

addResultToDOM('results of compose(curriedAdd(5), curriedSubtract(1), curriedMultiply(4), curriedDivide(2), curriedSum(3, 4))(1):', compose(curriedAdd(5), curriedSubtract(1), curriedMultiply(4), curriedDivide(2), curriedSum(3, 4))(1))