Mini-refactoring challenge 1: Friends & Pets

friends_pets.kt

/*
 * ~ Mini-refactoring challenge 1: Friends & Pets ~
 * Courtesy of https://twitter.com/ragunathjawahar
 *
 * Instruction
 * ===========
 * 1. Copy and paste the contents of this gist into a new file inside any open Kotlin project in your IDE.
 * 2. Delete it after you're done with the challenge.
 *
 * Objective
 * =========
 *  - Extract the logic within the lambda on line 27 as a function and move it to the `Friend` class.
 *
 * Rules for this challenge
 * ========================
 *  - You can't edit the source code inside the editor, that includes deleting characters.
 *  - You are allowed one copy-paste action.
 *  - You are allowed to use the keyboard for shortcuts and navigation.
 *  - Zero compilation errors during the process.
 */
import Pet.Cat
import Pet.Dog
import Pet.Parrot

private fun friendsWithDogs(): List<Friend> {
  return getFriends()
    .filter { it.pets.isNotEmpty() /* Objective: Move this logic into the `Friend` class! 😉 */ }
    .filter { it.pets.any { pet -> pet is Dog } }
}

data class Friend(val name: String, val pets: List<Pet>) {
  constructor(name: String, pet: Pet) : this(name, listOf(pet))
  constructor(name: String) : this(name, emptyList())
}

// ~~~ Don't change anything below this line ~~~ //

fun main() {
  friendsWithDogs()
    .onEach { println(it.name) }
}

sealed class Pet(open val name: String) {
  data class Dog(override val name: String) : Pet(name)
  data class Cat(override val name: String) : Pet(name)
  data class Parrot(override val name: String) : Pet(name)
}

private fun getFriends(): List<Friend> {
  val oreo = Dog("Oreo")

  return listOf(
    Friend("RMK", listOf(Dog("Raja"), Dog("Chippi"))),
    Friend("Trisha", oreo),
    Friend("Varsha", oreo),
    Friend("Vinay", Cat("Blackburn")),
    Friend("Ashish"),
    Friend("Nethra", Parrot("Ananya")),
  )
}