Deck tests

src/main/kotlin/eventDemo/app/entity/Deck.kt

@@ -4,27 +4,21 @@ import kotlinx.serialization.Serializable
 
 @Serializable
 data class Deck(
-    val stack: Set<Card> = emptySet(),
+    val stack: Stack = emptySet(),
     val discard: Set<Card> = emptySet(),
     val playersHands: PlayerHands = emptyMap(),
 ) {
     constructor(players: List<Player>) : this(playersHands = players.associateWith { emptyList<Card>() })
 
-    fun putOneCardOnDiscard(): Deck {
+    fun placeFirstCardOnDiscard(): Deck {
         val takenCard = stack.first()
-        val newStack = stack.filterNot { it != takenCard }.toSet()
+        return copy(
-        return copy(stack = newStack)
+            stack = stack - takenCard,
+            discard = discard + takenCard,
+        )
     }
 
-    private fun take(n: Int): Pair<Deck, List<Card>> {
+    fun takeOneCardFromStackTo(player: Player): Deck =
-        val takenCards = stack.take(n)
-        val newStack = stack.filterNot { takenCards.contains(it) }.toSet()
-        return Pair(copy(stack = newStack), takenCards)
-    }
-
-    private fun takeOne(): Pair<Deck, Card> = take(1).let { (deck, cards) -> Pair(deck, cards.first()) }
-
-    fun takeOneCardTo(player: Player): Deck =
         takeOne().let { (deck, newPlayerCard) ->
             val newHands =
                 deck.playersHands.mapValues { (p, cards) ->
@@ -52,26 +46,20 @@ data class Deck(
         }.let {
             copy(
                 discard = discard + card,
-                playersHands = playersHands.addCard(player, card),
+                playersHands = playersHands.removeCard(player, card),
             )
         }
 
+    private fun take(n: Int): Pair<Deck, List<Card>> {
+        val takenCards = stack.take(n)
+        val newStack = stack.filterNot { takenCards.contains(it) }.toSet()
+        return Pair(copy(stack = newStack), takenCards)
+    }
+
+    private fun takeOne(): Pair<Deck, Card> = take(1).let { (deck, cards) -> Pair(deck, cards.first()) }
+
     companion object {
-        fun initHands(
+        fun newWithoutPlayers(): Deck =
-            players: Set<Player>,
-            handSize: Int = 7,
-        ): Deck {
-            val deck = new()
-            val playersHands = players.associateWith { deck.stack.take(handSize) }
-            val allTakenCards = playersHands.flatMap { it.value }
-            val newStack = deck.stack.filterNot { allTakenCards.contains(it) }.toSet()
-            return deck.copy(
-                stack = newStack,
-                playersHands = playersHands,
-            )
-        }
-
-        private fun new(): Deck =
             listOf(Card.Color.Red, Card.Color.Blue, Card.Color.Yellow, Card.Color.Green)
                 .flatMap { color ->
                     ((0..9) + (1..9)).map { Card.NumericCard(it, color) } +
@@ -79,9 +67,27 @@ data class Deck(
                         (1..2).map { Card.ReverseCard(color) } +
                         (1..2).map { Card.PassCard(color) }
                 }.let {
-                    (1..4).map { Card.Plus4Card() }
+                    it + (1..4).map { Card.Plus4Card() }
                 }.shuffled()
                 .toSet()
                 .let { Deck(it) }
     }
 }
+
+fun Deck.initHands(
+    players: Set<Player>,
+    handSize: Int = 7,
+): Deck {
+    // Copy cards from stack to the player hands
+    val deckWithEmptyHands = copy(playersHands = players.associateWith { listOf() })
+    return players.fold(deckWithEmptyHands) { acc: Deck, player: Player ->
+        val hand = acc.stack.take(handSize)
+        val newStack = acc.stack.filterNot { card: Card -> hand.contains(card) }.toSet()
+        copy(
+            stack = newStack,
+            playersHands = acc.playersHands.addCards(player, hand),
+        )
+    }
+}
+
+typealias Stack = Set<Card>

src/main/kotlin/eventDemo/app/entity/PlayerHand.kt

@@ -5,7 +5,8 @@ typealias PlayerHands = Map<Player, List<Card>>
 fun PlayerHands.removeCard(
     player: Player,
     card: Card,
-) = mapValues { (p, cards) ->
+): PlayerHands =
+    mapValues { (p, cards) ->
         if (p == player) {
             cards - card
         } else {
@@ -16,7 +17,8 @@ fun PlayerHands.removeCard(
 fun PlayerHands.addCards(
     player: Player,
     newCards: List<Card>,
-) = mapValues { (p, cards) ->
+): PlayerHands =
+    mapValues { (p, cards) ->
         if (p == player) {
             cards + newCards
         } else {

src/main/kotlin/eventDemo/app/event/GameStateBuilder.kt

@@ -58,7 +58,7 @@ private fun GameId.buildStateFromEvents(events: List<GameEvent>): GameState =
             is PlayerHavePassEvent -> {
                 state.copy(
                     lastPlayer = event.player,
-                    deck = state.deck.takeOneCardTo(event.player),
+                    deck = state.deck.takeOneCardFromStackTo(event.player),
                 )
             }
 

src/main/kotlin/eventDemo/app/event/event/GameStartedEvent.kt

@@ -3,9 +3,10 @@ package eventDemo.app.event.event
 import eventDemo.app.entity.Deck
 import eventDemo.app.entity.GameId
 import eventDemo.app.entity.Player
+import eventDemo.app.entity.initHands
 
 /**
- * This [GameEvent] is sent when all players is ready.
+ * This [GameEvent] is sent when all players are ready.
  */
 data class GameStartedEvent(
     override val id: GameId,
@@ -20,7 +21,7 @@ data class GameStartedEvent(
             GameStartedEvent(
                 id = id,
                 firstPlayer = players.random(),
-                deck = Deck.initHands(players).putOneCardOnDiscard(),
+                deck = Deck.newWithoutPlayers().initHands(players).placeFirstCardOnDiscard(),
             )
     }
 }

src/test/kotlin/eventDemo/Helpers.kt

@@ -0,0 +1,8 @@
+package eventDemo
+
+import eventDemo.app.entity.Card
+import eventDemo.app.entity.Deck
+
+fun Deck.allCardCount(): Int = stack.size + discard.size + playersHands.values.flatten().size
+
+fun Deck.allCards(): Set<Card> = stack + discard + playersHands.values.flatten()

src/test/kotlin/eventDemo/app/entity/DeckTest.kt

@@ -0,0 +1,105 @@
+package eventDemo.app.entity
+
+import eventDemo.allCardCount
+import eventDemo.allCards
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.matchers.collections.shouldBeUnique
+import io.kotest.matchers.ints.shouldBeExactly
+import kotlin.test.assertNotNull
+
+class DeckTest :
+    FunSpec({
+        val totalCardsNumber = 104
+        test("newWithoutPlayers") {
+            // When
+            val deck = Deck.newWithoutPlayers()
+
+            // Then
+            deck.stack.size shouldBeExactly totalCardsNumber
+            deck.discard.size shouldBeExactly 0
+            deck.playersHands.size shouldBeExactly 0
+
+            deck.allCardCount() shouldBeExactly totalCardsNumber
+            deck.allCards().shouldBeUnique()
+            deck.allCards().map { it.id }.shouldBeUnique()
+        }
+
+        test("initHands") {
+            // Given
+            val playerNumbers = 4
+            val players = (1..playerNumbers).map { Player(name = "name $it") }.toSet()
+            val deck = Deck.newWithoutPlayers()
+
+            // When
+            val initDeck = deck.initHands(players)
+
+            // Then
+            initDeck.stack.size shouldBeExactly totalCardsNumber - (playerNumbers * 7)
+            initDeck.discard.size shouldBeExactly 0
+            initDeck.playersHands.size shouldBeExactly playerNumbers
+            initDeck.playersHands.forEach { (_, cards) -> cards.size shouldBeExactly 7 }
+            initDeck.allCardCount() shouldBeExactly totalCardsNumber
+        }
+
+        test("takeOneCardFromStackTo") {
+            // Given
+            val playerNumbers = 4
+            val players = (1..playerNumbers).map { Player(name = "name $it") }.toSet()
+            val deck = Deck.newWithoutPlayers().initHands(players)
+            val firstPlayer = players.first()
+
+            // When
+            val modifiedDeck = deck.takeOneCardFromStackTo(firstPlayer)
+
+            // Then
+            modifiedDeck.discard.size shouldBeExactly 0
+            modifiedDeck.stack.size shouldBeExactly totalCardsNumber - (playerNumbers * 7) - 1
+            modifiedDeck.playersHands.size shouldBeExactly playerNumbers
+            assertNotNull(modifiedDeck.playersHands[firstPlayer]).size shouldBeExactly 7 + 1
+            modifiedDeck.playersHands
+                .filterKeys { it != firstPlayer }
+                .forEach { (_, cards) -> cards.size shouldBeExactly 7 }
+            modifiedDeck.allCardCount() shouldBeExactly totalCardsNumber
+        }
+
+        test("putOneCardFromHand") {
+            // Given
+            val playerNumbers = 4
+            val players = (1..playerNumbers).map { Player(name = "name $it") }.toSet()
+            val deck = Deck.newWithoutPlayers().initHands(players)
+            val firstPlayer = players.first()
+
+            // When
+            val card = deck.playersHands[firstPlayer]!!.first()
+            val modifiedDeck = deck.putOneCardFromHand(firstPlayer, card)
+
+            // Then
+            modifiedDeck.discard.size shouldBeExactly 1
+            modifiedDeck.stack.size shouldBeExactly totalCardsNumber - (playerNumbers * 7)
+            modifiedDeck.playersHands.size shouldBeExactly playerNumbers
+            assertNotNull(modifiedDeck.playersHands[firstPlayer]).size shouldBeExactly 6
+            modifiedDeck.playersHands
+                .filterKeys { it != firstPlayer }
+                .forEach { (_, cards) -> cards.size shouldBeExactly 7 }
+            modifiedDeck.allCardCount() shouldBeExactly totalCardsNumber
+        }
+
+        test("placeFirstCardOnDiscard") {
+            // Given
+            val playerNumbers = 4
+            val players = (1..playerNumbers).map { Player(name = "name $it") }.toSet()
+            val deck = Deck.newWithoutPlayers().initHands(players)
+            val firstPlayer = players.first()
+
+            // When
+            val modifiedDeck = deck.placeFirstCardOnDiscard()
+
+            // Then
+            modifiedDeck.discard.size shouldBeExactly 1
+            modifiedDeck.stack.size shouldBeExactly totalCardsNumber - (playerNumbers * 7) - 1
+            modifiedDeck.playersHands.size shouldBeExactly playerNumbers
+            modifiedDeck.playersHands
+                .forEach { (_, cards) -> cards.size shouldBeExactly 7 }
+            modifiedDeck.allCardCount() shouldBeExactly totalCardsNumber
+        }
+    })