Kotlin mig: cards package

18 files changed, 239 insertions, 431 deletions

diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/Game.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/Game.java
index 2696adbf..1d88fb9f 100644
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/Game.java
+++ b/game-engine/src/main/java/org/luxons/sevenwonders/game/Game.java
@@ -109,7 +109,7 @@ public class Game {
     }
 
     public CardBack prepareMove(int playerIndex, PlayerMove playerMove) throws InvalidMoveException {
-        Card card = decks.getCard(playerMove.getCardName());
+        Card card = decks.getCard(table.getCurrentAge(), playerMove.getCardName());
         Move move = playerMove.getType().resolve(playerIndex, card, playerMove);
         validate(move);
         preparedMoves.put(playerIndex, move);
@@ -143,7 +143,7 @@ public class Game {
     private void rotateHandsIfRelevant() {
         // we don't rotate hands if some player can play his last card (with the special ability)
         if (!hands.maxOneCardRemains()) {
-            hands.rotate(table.getHandRotationDirection());
+            hands = hands.rotate(table.getHandRotationDirection());
         }
     }
 
@@ -196,7 +196,7 @@ public class Game {
     private void discardHand(int playerIndex) {
         List<Card> hand = hands.get(playerIndex);
         discardedCards.addAll(hand);
-        hand.clear();
+        hands = hands.discard(playerIndex);
     }
 
     private void removeFromHand(int playerIndex, Card card) {
diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Card.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Card.java
deleted file mode 100644
index 2d2f6777..00000000
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Card.java
+++ /dev/null
@@ -1,128 +0,0 @@
-package org.luxons.sevenwonders.game.cards;
-
-import java.util.List;
-import java.util.Objects;
-
-import org.luxons.sevenwonders.game.api.Table;
-import org.luxons.sevenwonders.game.boards.Board;
-import org.luxons.sevenwonders.game.effects.Effect;
-import org.luxons.sevenwonders.game.resources.ResourceTransactions;
-
-public class Card {
-
-    private final String name;
-
-    private final Color color;
-
-    private final Requirements requirements;
-
-    private final List<Effect> effects;
-
-    private final String chainParent;
-
-    private final List<String> chainChildren;
-
-    private final String image;
-
-    private CardBack back;
-
-    public Card(String name, Color color, Requirements requirements, List<Effect> effects, String chainParent,
-            List<String> chainChildren, String image) {
-        this.name = name;
-        this.color = color;
-        this.requirements = requirements;
-        this.chainParent = chainParent;
-        this.effects = effects;
-        this.chainChildren = chainChildren;
-        this.image = image;
-    }
-
-    public String getName() {
-        return name;
-    }
-
-    public Color getColor() {
-        return color;
-    }
-
-    public String getChainParent() {
-        return chainParent;
-    }
-
-    public Requirements getRequirements() {
-        return requirements;
-    }
-
-    public List<Effect> getEffects() {
-        return effects;
-    }
-
-    public List<String> getChainChildren() {
-        return chainChildren;
-    }
-
-    public String getImage() {
-        return image;
-    }
-
-    public CardBack getBack() {
-        return back;
-    }
-
-    public void setBack(CardBack back) {
-        this.back = back;
-    }
-
-    private boolean isAllowedOnBoard(Board board) {
-        return !board.isPlayed(name); // cannot play twice the same card
-    }
-
-    public boolean isChainableOn(Board board) {
-        return isAllowedOnBoard(board) && board.isPlayed(chainParent);
-    }
-
-    public boolean isFreeFor(Board board) {
-        if (!isAllowedOnBoard(board)) {
-            return false;
-        }
-        return isChainableOn(board) || (requirements.areMetWithoutNeighboursBy(board) && requirements.getGold() == 0);
-    }
-
-    public boolean isPlayable(Table table, int playerIndex) {
-        Board board = table.getBoard(playerIndex);
-        if (!isAllowedOnBoard(board)) {
-            return false;
-        }
-        return isChainableOn(board) || requirements.areMetBy(table, playerIndex);
-    }
-
-    public void applyTo(Table table, int playerIndex, ResourceTransactions transactions) {
-        Board playerBoard = table.getBoard(playerIndex);
-        if (!isChainableOn(playerBoard)) {
-            requirements.pay(table, playerIndex, transactions);
-        }
-        effects.forEach(e -> e.apply(table, playerIndex));
-    }
-
-    @Override
-    public boolean equals(Object o) {
-        if (this == o) {
-            return true;
-        }
-        if (o == null || getClass() != o.getClass()) {
-            return false;
-        }
-        Card card = (Card) o;
-        return Objects.equals(name, card.name);
-    }
-
-    @Override
-    public int hashCode() {
-        return Objects.hash(name);
-    }
-
-    @Override
-    public String toString() {
-        return "Card{" + name + '}';
-    }
-}
diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/CardBack.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/CardBack.java
deleted file mode 100644
index f925b6c4..00000000
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/CardBack.java
+++ /dev/null
@@ -1,14 +0,0 @@
-package org.luxons.sevenwonders.game.cards;
-
-public class CardBack {
-
-    private final String image;
-
-    public CardBack(String image) {
-        this.image = image;
-    }
-
-    public String getImage() {
-        return image;
-    }
-}
diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Color.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Color.java
deleted file mode 100644
index 80d06c55..00000000
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Color.java
+++ /dev/null
@@ -1,11 +0,0 @@
-package org.luxons.sevenwonders.game.cards;
-
-public enum Color {
-    BROWN,
-    GREY,
-    YELLOW,
-    BLUE,
-    GREEN,
-    RED,
-    PURPLE
-}
diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Decks.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Decks.java
deleted file mode 100644
index aa2b00bf..00000000
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Decks.java
+++ /dev/null
@@ -1,65 +0,0 @@
-package org.luxons.sevenwonders.game.cards;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-public class Decks {
-
-    private Map<Integer, List<Card>> cardsPerAge = new HashMap<>();
-
-    public Decks(Map<Integer, List<Card>> cardsPerAge) {
-        this.cardsPerAge = cardsPerAge;
-    }
-
-    public Card getCard(String cardName) throws CardNotFoundException {
-        return cardsPerAge.values()
-                          .stream()
-                          .flatMap(List::stream)
-                          .filter(c -> c.getName().equals(cardName))
-                          .findAny()
-                          .orElseThrow(() -> new CardNotFoundException(cardName));
-    }
-
-    public Hands deal(int age, int nbPlayers) {
-        List<Card> deck = getDeck(age);
-        validateNbCards(deck, nbPlayers);
-        return deal(deck, nbPlayers);
-    }
-
-    private List<Card> getDeck(int age) {
-        List<Card> deck = cardsPerAge.get(age);
-        if (deck == null) {
-            throw new IllegalArgumentException("No deck found for age " + age);
-        }
-        return deck;
-    }
-
-    private void validateNbCards(List<Card> deck, int nbPlayers) {
-        if (nbPlayers == 0) {
-            throw new IllegalArgumentException("Cannot deal cards between 0 players");
-        }
-        if (deck.size() % nbPlayers != 0) {
-            throw new IllegalArgumentException(
-                    String.format("Cannot deal %d cards evenly between %d players", deck.size(), nbPlayers));
-        }
-    }
-
-    private Hands deal(List<Card> deck, int nbPlayers) {
-        Map<Integer, List<Card>> hands = new HashMap<>(nbPlayers);
-        for (int i = 0; i < nbPlayers; i++) {
-            hands.put(i, new ArrayList<>());
-        }
-        for (int i = 0; i < deck.size(); i++) {
-            hands.get(i % nbPlayers).add(deck.get(i));
-        }
-        return new Hands(hands, nbPlayers);
-    }
-
-    class CardNotFoundException extends RuntimeException {
-        CardNotFoundException(String message) {
-            super(message);
-        }
-    }
-}
diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/HandRotationDirection.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/HandRotationDirection.java
deleted file mode 100644
index f3902fb5..00000000
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/HandRotationDirection.java
+++ /dev/null
@@ -1,21 +0,0 @@
-package org.luxons.sevenwonders.game.cards;
-
-public enum HandRotationDirection {
-    LEFT(-1),
-    RIGHT(1);
-
-    private final int indexOffset;
-
-    HandRotationDirection(int i) {
-        this.indexOffset = i;
-    }
-
-    public int getIndexOffset() {
-        return indexOffset;
-    }
-
-    public static HandRotationDirection forAge(int age) {
-        // clockwise (pass to the left) at age 1, and alternating
-        return age % 2 == 0 ? HandRotationDirection.RIGHT : HandRotationDirection.LEFT;
-    }
-}
diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Hands.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Hands.java
deleted file mode 100644
index 4a8bc143..00000000
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Hands.java
+++ /dev/null
@@ -1,64 +0,0 @@
-package org.luxons.sevenwonders.game.cards;
-
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.stream.Collectors;
-
-import org.luxons.sevenwonders.game.api.HandCard;
-import org.luxons.sevenwonders.game.api.Table;
-
-public class Hands {
-
-    private final int nbPlayers;
-
-    private Map<Integer, List<Card>> hands;
-
-    Hands(Map<Integer, List<Card>> hands, int nbPlayers) {
-        this.hands = hands;
-        this.nbPlayers = nbPlayers;
-    }
-
-    public List<Card> get(int playerIndex) {
-        if (!hands.containsKey(playerIndex)) {
-            throw new PlayerIndexOutOfBoundsException(playerIndex);
-        }
-        return hands.get(playerIndex);
-    }
-
-    public List<HandCard> createHand(Table table, int playerIndex) {
-        return hands.get(playerIndex)
-                    .stream()
-                    .map(c -> new HandCard(c, table, playerIndex))
-                    .collect(Collectors.toList());
-    }
-
-    public Hands rotate(HandRotationDirection direction) {
-        Map<Integer, List<Card>> newHands = new HashMap<>(hands.size());
-        for (int i = 0; i < nbPlayers; i++) {
-            int newIndex = Math.floorMod(i + direction.getIndexOffset(), nbPlayers);
-            newHands.put(newIndex, hands.get(i));
-        }
-        return new Hands(newHands, nbPlayers);
-    }
-
-    public boolean isEmpty() {
-        return hands.values().stream().allMatch(List::isEmpty);
-    }
-
-    public boolean maxOneCardRemains() {
-        return hands.values().stream().mapToInt(List::size).max().orElse(0) <= 1;
-    }
-
-    public List<Card> gatherAndClear() {
-        List<Card> remainingCards = hands.values().stream().flatMap(List::stream).collect(Collectors.toList());
-        hands.clear();
-        return remainingCards;
-    }
-
-    class PlayerIndexOutOfBoundsException extends ArrayIndexOutOfBoundsException {
-        PlayerIndexOutOfBoundsException(int index) {
-            super(index);
-        }
-    }
-}
diff --git a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Requirements.java b/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Requirements.java
deleted file mode 100644
index 8c7245ed..00000000
--- a/game-engine/src/main/java/org/luxons/sevenwonders/game/cards/Requirements.java
+++ /dev/null
@@ -1,108 +0,0 @@
-package org.luxons.sevenwonders.game.cards;
-
-import org.luxons.sevenwonders.game.api.Table;
-import org.luxons.sevenwonders.game.boards.Board;
-import org.luxons.sevenwonders.game.resources.BestPriceCalculator;
-import org.luxons.sevenwonders.game.resources.ResourceTransactions;
-import org.luxons.sevenwonders.game.resources.Resources;
-
-public class Requirements {
-
-    private int gold;
-
-    private Resources resources = new Resources();
-
-    public int getGold() {
-        return gold;
-    }
-
-    public void setGold(int gold) {
-        this.gold = gold;
-    }
-
-    public Resources getResources() {
-        return resources;
-    }
-
-    public void setResources(Resources resources) {
-        this.resources = resources;
-    }
-
-    /**
-     * Returns whether the given board meets these requirements on its own.
-     *
-     * @param board
-     *         the board to check
-     *
-     * @return true if the given board meets these requirements without any transaction with its neighbours
-     */
-    boolean areMetWithoutNeighboursBy(Board board) {
-        return hasRequiredGold(board) && producesRequiredResources(board);
-    }
-
-    /**
-     * Returns whether the given board meets these requirements, if the specified resources are bought from neighbours.
-     *
-     * @param board
-     *         the board to check
-     * @param boughtResources
-     *         the resources the player intends to buy
-     *
-     * @return true if the given board meets these requirements
-     */
-    public boolean areMetWithHelpBy(Board board, ResourceTransactions boughtResources) {
-        if (!hasRequiredGold(board, boughtResources)) {
-            return false;
-        }
-        if (producesRequiredResources(board)) {
-            return true;
-        }
-        return producesRequiredResourcesWithHelp(board, boughtResources);
-    }
-
-    /**
-     * Returns whether the given player's board meets these requirements, either on its own or by buying resources to
-     * neighbours.
-     *
-     * @param table
-     *         the current game table
-     * @param playerIndex
-     *         the index of the player to check
-     *
-     * @return true if the given player's board could meet these requirements
-     */
-    boolean areMetBy(Table table, int playerIndex) {
-        Board board = table.getBoard(playerIndex);
-        if (!hasRequiredGold(board)) {
-            return false;
-        }
-        if (producesRequiredResources(board)) {
-            return true;
-        }
-        return BestPriceCalculator.bestPrice(resources, table, playerIndex) <= board.getGold() - gold;
-    }
-
-    private boolean hasRequiredGold(Board board) {
-        return board.getGold() >= gold;
-    }
-
-    private boolean hasRequiredGold(Board board, ResourceTransactions resourceTransactions) {
-        int resourcesPrice = board.getTradingRules().computeCost(resourceTransactions);
-        return board.getGold() >= gold + resourcesPrice;
-    }
-
-    private boolean producesRequiredResources(Board board) {
-        return board.getProduction().contains(resources);
-    }
-
-    private boolean producesRequiredResourcesWithHelp(Board board, ResourceTransactions transactions) {
-        Resources totalBoughtResources = transactions.asResources();
-        Resources remainingResources = this.resources.minus(totalBoughtResources);
-        return board.getProduction().contains(remainingResources);
-    }
-
-    public void pay(Table table, int playerIndex, ResourceTransactions transactions) {
-        table.getBoard(playerIndex).removeGold(gold);
-        transactions.execute(table, playerIndex);
-    }
-}
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/HandCard.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/HandCard.kt
index 4c3a7a8d..d487a9ac 100644
--- a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/HandCard.kt
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/HandCard.kt
@@ -12,12 +12,11 @@ class HandCard(val card: Card, table: Table, playerIndex: Int) {
 
     val isFree: Boolean
 
-    val isPlayable: Boolean
+    val isPlayable: Boolean = card.isPlayable(table, playerIndex)
 
     init {
         val board = table.getBoard(playerIndex)
         this.isChainable = card.isChainableOn(board)
         this.isFree = card.isFreeFor(board)
-        this.isPlayable = card.isPlayable(table, playerIndex)
     }
 }
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/PlayerMove.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/PlayerMove.kt
index d0a1e1b3..4d4ef7cc 100644
--- a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/PlayerMove.kt
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/PlayerMove.kt
@@ -3,8 +3,8 @@ package org.luxons.sevenwonders.game.api
 import org.luxons.sevenwonders.game.moves.MoveType
 import org.luxons.sevenwonders.game.resources.ResourceTransaction
 
-data class PlayerMove(
+data class PlayerMove @JvmOverloads constructor(
     val type: MoveType,
-    val cardName: String?,
+    val cardName: String,
     val transactions: Collection<ResourceTransaction> = emptyList()
 )
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/Table.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/Table.kt
index 9ecfa6b0..60287c84 100644
--- a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/Table.kt
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/api/Table.kt
@@ -40,18 +40,18 @@ class Table(val boards: List<Board>) {
         for (i in 0 until nbPlayers) {
             val board1 = getBoard(i)
             val board2 = getBoard((i + 1) % nbPlayers)
-            resolveConflict(board1, board2, currentAge)
+            resolveConflict(board1, board2)
         }
     }
 
-    private fun resolveConflict(board1: Board, board2: Board, age: Int) {
+    private fun resolveConflict(board1: Board, board2: Board) {
         val shields1 = board1.military.nbShields
         val shields2 = board2.military.nbShields
         if (shields1 < shields2) {
             board1.military.defeat()
-            board2.military.victory(age)
+            board2.military.victory(currentAge)
         } else if (shields1 > shields2) {
-            board1.military.victory(age)
+            board1.military.victory(currentAge)
             board2.military.defeat()
         }
     }
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Cards.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Cards.kt
new file mode 100644
index 00000000..cf94bef4
--- /dev/null
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Cards.kt
@@ -0,0 +1,52 @@
+package org.luxons.sevenwonders.game.cards
+
+import org.luxons.sevenwonders.game.api.Table
+import org.luxons.sevenwonders.game.boards.Board
+import org.luxons.sevenwonders.game.effects.Effect
+import org.luxons.sevenwonders.game.resources.ResourceTransactions
+
+data class CardBack(val image: String)
+
+data class Card(
+    val name: String,
+    val color: Color,
+    val requirements: Requirements,
+    val effects: List<Effect>,
+    val chainParent: String?,
+    val chainChildren: List<String>,
+    val image: String,
+    val back: CardBack
+) {
+    private fun isAllowedOnBoard(board: Board): Boolean = !board.isPlayed(name) // cannot play twice the same card
+
+    fun isFreeFor(board: Board): Boolean = isChainableOn(board) || isFreeWithoutChainingOn(board)
+
+    fun isChainableOn(board: Board): Boolean =
+        isAllowedOnBoard(board) && chainParent != null && board.isPlayed(chainParent)
+
+    private fun isFreeWithoutChainingOn(board: Board) =
+        isAllowedOnBoard(board) && requirements.areMetWithoutNeighboursBy(board) && requirements.gold == 0
+
+    fun isPlayable(table: Table, playerIndex: Int): Boolean {
+        val board = table.getBoard(playerIndex)
+        return isAllowedOnBoard(board) && (isChainableOn(board) || requirements.areMetBy(table, playerIndex))
+    }
+
+    fun applyTo(table: Table, playerIndex: Int, transactions: ResourceTransactions) {
+        val playerBoard = table.getBoard(playerIndex)
+        if (!isChainableOn(playerBoard)) {
+            requirements.pay(table, playerIndex, transactions)
+        }
+        effects.forEach { e -> e.apply(table, playerIndex) }
+    }
+}
+
+enum class Color {
+    BROWN,
+    GREY,
+    YELLOW,
+    BLUE,
+    GREEN,
+    RED,
+    PURPLE
+}
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Decks.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Decks.kt
new file mode 100644
index 00000000..bd7b4bde
--- /dev/null
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Decks.kt
@@ -0,0 +1,38 @@
+package org.luxons.sevenwonders.game.cards
+
+fun List<Card>.deal(nbPlayers: Int): Hands {
+    val hands: Map<Int, List<Card>> = this.withIndex()
+        .groupBy { (index, _) -> index % nbPlayers }
+        .mapValues { it.value.map { (_, cards) -> cards } }
+
+    val allHands = List(nbPlayers) { i -> hands[i] ?: emptyList() }
+    return Hands(allHands)
+}
+
+class Decks(private val cardsPerAge: Map<Int, List<Card>>) {
+
+    @Throws(Decks.CardNotFoundException::class)
+    fun getCard(age: Int, cardName: String): Card =
+        getDeck(age).firstOrNull { c -> c.name == cardName } ?: throw CardNotFoundException(cardName)
+
+    fun deal(age: Int, nbPlayers: Int): Hands {
+        val deck = getDeck(age)
+        validateNbCards(deck, nbPlayers)
+        return deck.deal(nbPlayers)
+    }
+
+    private fun getDeck(age: Int): List<Card> {
+        return cardsPerAge[age] ?: throw IllegalArgumentException("No deck found for age $age")
+    }
+
+    private fun validateNbCards(deck: List<Card>, nbPlayers: Int) {
+        if (nbPlayers == 0) {
+            throw IllegalArgumentException("Cannot deal cards between 0 players")
+        }
+        if (deck.size % nbPlayers != 0) {
+            throw IllegalArgumentException("Cannot deal ${deck.size} cards evenly between $nbPlayers players")
+        }
+    }
+
+    inner class CardNotFoundException(message: String) : RuntimeException(message)
+}
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/HandRotationDirection.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/HandRotationDirection.kt
new file mode 100644
index 00000000..13494175
--- /dev/null
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/HandRotationDirection.kt
@@ -0,0 +1,15 @@
+package org.luxons.sevenwonders.game.cards
+
+enum class HandRotationDirection {
+    LEFT,
+    RIGHT;
+
+    companion object {
+
+        fun forAge(age: Int): HandRotationDirection {
+            // clockwise (pass to the left) at age 1, and alternating
+            return if (age % 2 == 0) HandRotationDirection.RIGHT else HandRotationDirection.LEFT
+        }
+    }
+}
+
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Hands.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Hands.kt
new file mode 100644
index 00000000..35d3599a
--- /dev/null
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Hands.kt
@@ -0,0 +1,32 @@
+package org.luxons.sevenwonders.game.cards
+
+import org.luxons.sevenwonders.game.api.HandCard
+import org.luxons.sevenwonders.game.api.Table
+
+class Hands internal constructor(private val hands: List<List<Card>>) {
+
+    val isEmpty: Boolean = this.hands.all(List<Card>::isEmpty)
+
+    operator fun get(playerIndex: Int): List<Card> {
+        return hands[playerIndex]
+    }
+
+    fun discard(playerIndex: Int): Hands {
+        val newHands = hands.mapIndexed { index, hand -> if (index == playerIndex) emptyList() else hand }
+        return Hands(newHands)
+    }
+
+    fun createHand(table: Table, playerIndex: Int): List<HandCard> {
+        return hands[playerIndex].map { c -> HandCard(c, table, playerIndex) }
+    }
+
+    fun rotate(direction: HandRotationDirection): Hands {
+        val newHands = when (direction) {
+            HandRotationDirection.RIGHT -> hands.takeLast(1) + hands.dropLast(1)
+            HandRotationDirection.LEFT -> hands.drop(1) + hands.take(1)
+        }
+        return Hands(newHands)
+    }
+
+    fun maxOneCardRemains(): Boolean = hands.map { it.size }.max() ?: 0 <= 1
+}
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Requirements.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Requirements.kt
new file mode 100644
index 00000000..e04fa7a0
--- /dev/null
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/cards/Requirements.kt
@@ -0,0 +1,84 @@
+package org.luxons.sevenwonders.game.cards
+
+import org.luxons.sevenwonders.game.api.Table
+import org.luxons.sevenwonders.game.boards.Board
+import org.luxons.sevenwonders.game.resources.BestPriceCalculator
+import org.luxons.sevenwonders.game.resources.ResourceTransactions
+import org.luxons.sevenwonders.game.resources.Resources
+
+data class Requirements @JvmOverloads constructor(
+    val gold: Int = 0,
+    val resources: Resources = Resources()
+) {
+    /**
+     * Returns whether the given [board] meets these requirements on its own.
+     *
+     * @param board the board to check
+     *
+     * @return true if the given board meets these requirements without any transaction with its neighbours
+     */
+    fun areMetWithoutNeighboursBy(board: Board): Boolean {
+        return hasRequiredGold(board) && producesRequiredResources(board)
+    }
+
+    /**
+     * Returns whether the given board meets these requirements, if the specified resources are bought from neighbours.
+     *
+     * @param board the board to check
+     * @param boughtResources the resources the player intends to buy
+     *
+     * @return true if the given board meets these requirements
+     */
+    fun areMetWithHelpBy(board: Board, boughtResources: ResourceTransactions): Boolean {
+        if (!hasRequiredGold(board, boughtResources)) {
+            return false
+        }
+        return if (producesRequiredResources(board)) {
+            true
+        } else producesRequiredResourcesWithHelp(board, boughtResources)
+    }
+
+    /**
+     * Returns whether the given player's board meets these requirements, either on its own or by buying resources to
+     * neighbours.
+     *
+     * @param table the current game table
+     * @param playerIndex the index of the player to check
+     *
+     * @return true if the given player's board could meet these requirements
+     */
+    fun areMetBy(table: Table, playerIndex: Int): Boolean {
+        val board = table.getBoard(playerIndex)
+        if (!hasRequiredGold(board)) {
+            return false
+        }
+        if (producesRequiredResources(board)) {
+            return true
+        }
+        return BestPriceCalculator.bestPrice(resources, table, playerIndex) <= board.gold - gold
+    }
+
+    private fun hasRequiredGold(board: Board): Boolean {
+        return board.gold >= gold
+    }
+
+    private fun hasRequiredGold(board: Board, resourceTransactions: ResourceTransactions): Boolean {
+        val resourcesPrice = board.tradingRules.computeCost(resourceTransactions)
+        return board.gold >= gold + resourcesPrice
+    }
+
+    private fun producesRequiredResources(board: Board): Boolean {
+        return board.production.contains(resources)
+    }
+
+    private fun producesRequiredResourcesWithHelp(board: Board, transactions: ResourceTransactions): Boolean {
+        val totalBoughtResources = transactions.asResources()
+        val remainingResources = this.resources.minus(totalBoughtResources)
+        return board.production.contains(remainingResources)
+    }
+
+    fun pay(table: Table, playerIndex: Int, transactions: ResourceTransactions) {
+        table.getBoard(playerIndex).removeGold(gold)
+        transactions.execute(table, playerIndex)
+    }
+}
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/CardDefinition.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/CardDefinition.kt
index 2827564b..3f42746c 100644
--- a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/CardDefinition.kt
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/CardDefinition.kt
@@ -1,20 +1,22 @@
 package org.luxons.sevenwonders.game.data.definitions
 
 import org.luxons.sevenwonders.game.cards.Card
+import org.luxons.sevenwonders.game.cards.CardBack
 import org.luxons.sevenwonders.game.cards.Color
 import org.luxons.sevenwonders.game.cards.Requirements
 
 internal class CardDefinition(
     private val name: String,
     private val color: Color,
-    private val requirements: Requirements? = null,
+    private val requirements: Requirements = Requirements(),
     private val effect: EffectsDefinition,
     private val chainParent: String? = null,
     private val chainChildren: List<String> = emptyList(),
-    private val image: String? = null,
+    private val image: String,
     private val countPerNbPlayer: Map<Int, Int>
 ) {
-    fun create(nbPlayers: Int): List<Card> = List( countPerNbPlayer[nbPlayers]!!) { create() }
+    fun create(back: CardBack, nbPlayers: Int): List<Card> = List(countPerNbPlayer[nbPlayers] ?: 0) { create(back) }
 
-    fun create(): Card = Card(name, color, requirements, effect.create(), chainParent, chainChildren, image)
+    fun create(back: CardBack): Card =
+        Card(name, color, requirements, effect.create(), chainParent, chainChildren, image, back)
 }
diff --git a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/DecksDefinition.kt b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/DecksDefinition.kt
index a09f0642..bc025ea2 100644
--- a/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/DecksDefinition.kt
+++ b/game-engine/src/main/kotlin/org/luxons/sevenwonders/game/data/definitions/DecksDefinition.kt
@@ -39,14 +39,11 @@ internal class DecksDefinition(
     }
 
     private fun createDeck(defs: List<CardDefinition>, settings: Settings, back: CardBack): List<Card> {
-        return defs.flatMap { it.create(settings.nbPlayers) }.onEach { it.back = back }
+        return defs.flatMap { it.create(back, settings.nbPlayers) }
     }
 
     private fun createGuildCards(settings: Settings, back: CardBack): List<Card> {
-        val guild = guildCards
-            .map { it.create() }
-            .map { c -> c.back = back; c }
-            .toMutableList()
+        val guild = guildCards.map { it.create(back) }.toMutableList()
         guild.shuffle(settings.random)
         return guild.subList(0, settings.nbPlayers + 2)
     }