case class Card(rank: Int, suit: Int) { override def toString = s"${"23456789TJQKA" rank}${"♣♠♦♥" suit}" }

object HandType extends Enumeration {
  val HighCard, OnePair, TwoPair, ThreeOfAKind, Straight, Flush, FullHouse, FourOfAKind, StraightFlush = Value
}

case class Hand(hand: Set[Card]) {
  val (handType, sorted) = {
    def rankMatches(card: Card) = hand count (_.rank == card.rank)
    val groups = hand groupBy rankMatches mapValues {_.toList.sorted}

    val isFlush = (hand groupBy {_.suit}).size == 1
    val isWheel = "A2345" forall {r => hand exists (_.rank == Card.ranks.indexOf(r))}   // A,2,3,4,5 straight
    val isStraight = groups.size == 1 && (hand.max.rank - hand.min.rank) == 4 || isWheel
    val (isThreeOfAKind, isOnePair) = (groups contains 3, groups contains 2)

    val handType = if (isStraight && isFlush)     HandType.StraightFlush
      else if (groups contains 4)                 HandType.FourOfAKind
      else if (isThreeOfAKind && isOnePair)       HandType.FullHouse
      else if (isFlush)                           HandType.Flush
      else if (isStraight)                        HandType.Straight
      else if (isThreeOfAKind)                    HandType.ThreeOfAKind
      else if (isOnePair && groups(2).size == 4)  HandType.TwoPair
      else if (isOnePair)                         HandType.OnePair
      else                                        HandType.HighCard

    val kickers = ((1 until 5) flatMap groups.get).flatten.reverse
    require(hand.size == 5 && kickers.size == 5)
    (handType, if (isWheel) (kickers takeRight 4) :+ kickers.head else kickers)
  }
}

object Hand {
  import scala.math.Ordering.Implicits._
  implicit val rankOrdering = Ordering by {hand: Hand => (hand.handType, hand.sorted)}
}