data class Card(val weight: Weight, val suit: Suit)

val isStraightFlush; get() = isStraight && isFlush

val isFourOfAKind = cards.groupBy { it.weight }.map { it.value }.any { it.size == 4 }

val isFullHouse = cards.groupBy { it.weight }.map { it.value }.size == 2

val isFlush = cards.groupBy { it.suit }.map { it.value }.size == 1

val isStraight = cards.map { it.weight.ordinal } ==
        (cards[0].weight.ordinal..cards[0].weight.ordinal + 4).toList()

val isThreeOfAKind = cards.groupBy { it.weight }.map { it.value }.any { it.size == 3 }

val isTwoPair = cards.groupBy { it.weight }.map { it.value }.filter { it.size == 2 }.count() == 2

val isPair = cards.groupBy { it.weight }.map { it.value }.any { it.size == 2 }

 override fun compareTo(other: PokerHand): Int = when {
     (this.isStraightFlush || other.isStraightFlush) ->
         if (this.isStraightFlush) if (!other.isStraightFlush) WIN else compareByHighCard(other) else LOSS
     (this.isFourOfAKind || other.isFourOfAKind) ->
         if (this.isFourOfAKind) if (!other.isFourOfAKind) WIN else compareByHighCard(other) else LOSS
     (this.isFullHouse || other.isFullHouse) ->
         if (this.isFullHouse) if (!other.isFullHouse) WIN else compareByHighCard(other) else LOSS
     (this.isFlush || other.isFlush) ->
         if (this.isFlush) if (!other.isFlush) WIN else compareByHighCard(other) else LOSS
     (this.isStraight || other.isStraight) ->
         if (this.isStraight) if (!other.isStraight) WIN else compareByHighCard(other) else LOSS
     (this.isThreeOfAKind || other.isThreeOfAKind) ->
         if (this.isThreeOfAKind) if (!other.isThreeOfAKind) WIN else compareByHighCard(other) else LOSS
     (this.isTwoPair || other.isTwoPair) ->
         if (this.isTwoPair) if (!other.isTwoPair) WIN else compareByHighCard(other) else LOSS
     (this.isPair || other.isPair) ->
         if (this.isPair) if (!other.isPair) WIN else compareByHighCard(other) else LOSS
     else -> compareByHighCard(other)
 }

@Test
fun compareTo() {
    test(LOSS,  "2H 3H 4H 5H 6H", "KS AS TS QS JS", "The highest straight flush wins")
    test(WIN,   "2H 3H 4H 5H 6H", "AS AD AC AH JD", "A straight flush wins over 4 of a kind")
    test(WIN,   "AS AH 2H AD AC", "JS JD JC JH 3D", "The highest 4 of a kind wins")
    test(LOSS,  "2S AH 2H AS AC", "JS JD JC JH AD", "4 Of a kind wins over a full house")
    test(WIN,   "2S AH 2H AS AC", "2H 3H 5H 6H 7H", "A full house wins over a flush")
    test(WIN,   "AS 3S 4S 8S 2S", "2H 3H 5H 6H 7H", "The highest flush wins")
    test(WIN,   "2H 3H 5H 6H 7H", "2S 3H 4H 5S 6C", "A flush wins over a straight")
    test(TIE,   "2S 3H 4H 5S 6C", "3D 4C 5H 6H 2S", "Equal straight is tie")
    test(WIN,   "2S 3H 4H 5S 6C", "AH AC 5H 6H AS", "A straight wins over three of a kind")
    test(LOSS,  "2S 2H 4H 5S 4C", "AH AC 5H 6H AS", "3 Of a kind wins over a two pair")
    test(WIN,   "2S 2H 4H 5S 4C", "AH AC 5H 6H 7S", "A 2 pair wins over a pair")
    test(LOSS,  "6S AD 7H 4S AS", "AH AC 5H 6H 7S", "The highest pair wins")
    test(LOSS,  "2S AH 4H 5S KC", "AH AC 5H 6H 7S", "A pair wins over a dud hand")
    test(LOSS,  "8C 4S KH JS 4D", "KC 4H KS 2H 8D", "Both sides with pairs, the high card side wins")
    test(WIN,   "KD 6S 9D TH AD", "JH 8S TH AH QH", "A dud hands beats another dud hand, by high card")
    test(TIE,   "2S AH 4H 5S 6C", "AD 4C 5H 6H 2C", "Equal dud cards tie")
}