//: Filter, Map, Reduce - Interview question

FilterMapReduce.swift

//: Filter, Map, Reduce - Interview question

import UIKit

// Our Skate shop just got a big order of wheels delivered
// We enter the wheels into the system like this:

struct Wheel {
  let brand: String
  let color: String
  let size:  Int
  var price: Double
}

// Today's shipment included:

var Stacked     = Wheel(brand: "Baker", color: "orange", size: 52, price: 24.99)
var OneHundreds = Wheel(brand: "Bones", color: "white", size: 54, price: 23.99)
var Haslam      = Wheel(brand: "Bones", color: "white", size: 52, price: 32.99)
var Party       = Wheel(brand: "Bones", color: "multi", size: 53, price: 23.99)
var HardBoiled  = Wheel(brand: "OJ", color: "orange", size: 54, price: 29.99)
var BlackCats   = Wheel(brand: "OJ", color: "black", size: 58, price: 29.99)
var HouseBrand  = Wheel(brand: "HouseBrand", color: "white", size: 50, price: 14.99)
var Classic     = Wheel(brand: "Spitfire", color: "white", size: 56, price: 32.99)
var BigSwirl    = Wheel(brand: "Spitfire", color: "multi", size: 51, price: 26.99)

// One of the shop guys put them in the case
var allWheels = [
  Stacked, OneHundreds, Haslam, Party, HardBoiled,
  BlackCats, HouseBrand, Classic, BigSwirl
]


//MARK: - Filter
// A lot has changed in how we operate things in our shop.
// For example, when a team rider needed wheels for a tour.
// The riders usually stick to one size of wheel, so we
// would pick them out like this:

func getRiderWheels2017(size: Int) -> [Wheel] {
  var wheels = [Wheel]()

  for wheel in allWheels {
    if wheel.size == size {
      wheels.append(wheel)
    }
  }

  return wheels
}

// It worked but it wasn't really efficient,
// so we decided to do it another way:

func getRiderWheels2018(size: Int) -> [Wheel] {
  return allWheels.filter { $0.size == size }
}

// This saved us a lot of time...which is awesome!


// MARK: - Map
// We also have sales on wheels in the summer.
// Last summer the staff marked down the prices like this:

func markDownPrices2017(by percentage: Double) {
  var saleWheels = [Wheel]()

  for wheel in allWheels {
    var wheel = wheel
    wheel.price = wheel.price - ((percentage / 100) * wheel.price)
    saleWheels.append(wheel)
  }

  allWheels = saleWheels
}

// This worked. But again, it was a lot
// of extra work. We decided to try something
// new this summer

func markDownPrices2018(by percentage: Double) {
  allWheels = allWheels.map { wheel in
    let price = wheel.price - ((percentage / 100) * wheel.price)
    return Wheel(brand: wheel.brand, color: wheel.color, size: wheel.size, price: price)
  }
}

// It may seem like the same amount of work, but
// we never created `saleWheels`. That means the
// wheels could stay in the case without being moved.
// Pretty sweet.


// MARK: - Reduce
// Like every business we have to audit our inventory.
// Last year, it took forever doing it this way:

func totalWheelInventoryValue2017() -> Double {
  var totalValue: Double = 0.0
  for wheel in allWheels {
    totalValue += wheel.price
  }
  return totalValue
}

// It was a nightmare. Fortunately, we came up
// with a new way to do things using our new skills.

func totalWheelInventoryValue2018() -> Double {
  let wheelPrices = allWheels.map { return $0.price }
  return wheelPrices.reduce(0, +)
}

// As you can see we really "reduced" the amount
// of work involved. ;)

// So that's how our skate shop is doing business
// nowadays. We have really improved the efficiency
// so now we have more time to watch skate videos!