gistfile1.scala

import util.Random

/*
Takes a sequence of secret santa participants and suggests who should give to who
*/

object SecretSanta {

  def main(args: Array[String]){

    val people = args.toSet

    if (people.size<3){
      println("Secret santa with less than 3 people is silly")
      sys.exit()
    }

    val pairs = scala.collection.mutable.Map[String, String]()

    people foreach { person =>

      def getPersonToGiveTo(candidates: Set[String]): Option[String] = {

        def notBeingGivenYet(p: String): Boolean = !pairs.values.exists(_==p)

        def notGivingToMe(p: String): Boolean = pairs.get(p) match{
          case Some(receiver) if receiver==person => false
          case _ => true
        }

        Random.shuffle(candidates filter notBeingGivenYet filter notGivingToMe).headOption
      }

      val peopleNotMe = people.filterNot(_ == person)

      getPersonToGiveTo(peopleNotMe) match{
        case Some(luckyPerson) => pairs += person -> luckyPerson
        case None => {}
      }

    }

    println("Secret santa happy times! \n")
    pairs foreach { happyCouple =>
      println("%s should give to %s".format(happyCouple._1, happyCouple._2))
    }

  }

}