Dinner.scala

package code

import cats.implicits._

// Main.scala

object Main extends App {
  val database = PersonDatabase.createTestDatabase

  // 1. Write code to:
  //     - Determine whether one person knows another through a chain of intermediate friends.
  //
  //     - Given a key person P and a number N,
  //       find a list of N transitive friends of P to invite to a dinner party.
  //
  //     - Given a list of dinner party attendees, work out what to serve!
  //
  // 2. Change the return type of PersonDatabase to Option[Person].
  //    Make everything work!
  //
  // 3. Change the return type of PersonDatabase to Future[Person].
  //    Make everything work!
  //
  // 4. Change the return type of PersonDabase to F[Person] where F is a monad.
  //    Make everything work!
}

// Person.scala

case class Person(name: String, favoriteFood: String, friends: List[String])

// PersonDatabase.scala

class PersonDatabase(people: List[Person]) {
  def find(name: String): Person =
    people.find(_.name == name).getOrElse(throw new Exception(s"Person not found: $name"))
}

object PersonDatabase {
  def createTestDatabase: PersonDatabase =
    new PersonDatabase(List(
      Person(name = "Alice"   , favoriteFood = "Pizza"     , friends = List("Bob",    "Gina"    )),
      Person(name = "Bob"     , favoriteFood = "Ice cream" , friends = List("Iris",   "Liam"    )),
      Person(name = "Charlie" , favoriteFood = "Roast"     , friends = List("Bob",    "Iris"    )),
      Person(name = "Declan"  , favoriteFood = "Pizza"     , friends = List("Gina",   "Juan"    )),
      Person(name = "Erica"   , favoriteFood = "Ice cream" , friends = List("Iris",   "Charlie" )),
      Person(name = "Frank"   , favoriteFood = "Roast"     , friends = List("Liam",   "Henrick" )),
      Person(name = "Gina"    , favoriteFood = "Pizza"     , friends = List("Declan", "Bob"     )),
      Person(name = "Henrick" , favoriteFood = "Ice cream" , friends = List("Declan", "Erica"   )),
      Person(name = "Iris"    , favoriteFood = "Pizza"     , friends = List("Kevin",  "Frank"   )),
      Person(name = "Juan"    , favoriteFood = "Ice cream" , friends = List("Alice",  "Bob"     )),
      Person(name = "Kevin"   , favoriteFood = "Roast"     , friends = List("Alice",  "Gina"    )),
      Person(name = "Liam"    , favoriteFood = "Pizza"     , friends = List("Erica",  "Frank"   )),
    ))
}