shopifyFall2017.js

// Requirements
// 
// 
// Read all orders from the paginated API.
// Any order without cookies can be fulfilled.
// Prioritize fulfilling orders with the highest amount of cookies.
// If orders have the same amount of cookies, prioritize the order with the lowest ID.
// If an order has an amount of cookies bigger than the remaining cookies, skip the order.
// 
// 
// 
// What to submit: 
// 
// Output (in JSON)
// 
// {
//   "remaining_cookies": "Amount of cookies remaining after trying to fulfill orders",
//   "unfulfilled_orders": [ "IDs of the order that couldn't be fulfilled in ascending order" ]
// }
// 
// 
// 
// *Example Answer Output
// 
// {
//   "remaining_cookies": 0,
//   "unfulfilled_orders": [ 3, 5 ]
// }

const rp = require('request-promise')

const BASE_URI = 'https://backend-challenge-fall-2017.herokuapp.com/orders.json'
const options = {
  uri: BASE_URI,
  qs: {},
  json: true,
}
let remainingCookies 

// Makes a get request to the base uri and 
// adds a query string for pagnation
function getPage(page, index = 0) {
  const pageOptions = Object.assign(
    options, 
    { qs: { page: index + 1 } }
  )
  return rp(pageOptions)
}

// Returns a new order object that contains
// cookie order details and id
function cookiesOnly(order) {
  return Object.assign(
    order.products.find(product => product.title === 'Cookie') || {},
    { id: order.id }
  )
}

// Sorts orders in decending order based
// off amounts, then id
function decendingSort(a, b) {
  if (b.amount === a.amount) return a.id - b.id
  return b.amount - a.amount
}

// Gets the results of pages
const pages = getPage()
  .then((res) => {
    const { total } = res.pagination
    const pages = []
    pages.length = total
    remainingCookies = res.available_cookies
    return pages
  })
  .map(getPage)

// Maps out all the orders
const orders = pages
  .map(page => page.orders)
  .reduce((prev = [], current) => prev.concat(current), [])

// Finds only the cookie orders
const cookieOrders = orders
  .filter(order => !order.fulfilled)
  .map(cookiesOnly)
  .filter(order => order.amount)

// Finds the orders that cannot be furfilled
const unfulfilledOrders = cookieOrders
  .then(order => order.sort(decendingSort))
  .reduce((orders, order) => {
    if (order.amount > remainingCookies) return orders.concat(order)
    remainingCookies -= order.amount 
    return orders
  }, [])

// Creates the respones for unfurfilled orders
unfulfilledOrders
  .map(order => order.id)
  .then((ids) => {
    const result = {
      remaining_cookies: remainingCookies,
      unfulfilled_orders: ids,
    }
    console.log(JSON.stringify(result, null, 2))
  })

// RESULTS
// {
//   "remaining_cookies": 0,
//   "unfulfilled_orders": [
//     8,
//     7,
//     11
//   ]
// }