mancala/apps/backend-quarkus/src/main/java/app/playmancala/engine/Board.java

package app.playmancala.engine;

import java.util.ArrayList;
import java.util.List;
import java.util.function.IntConsumer;

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

// Port of packages/mancala.js/src/core/Board.ts. Pits are indexed counterclockwise: player 1's pits, player 1's bank,
// player 2's pits, player 2's bank.
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility = JsonAutoDetect.Visibility.NONE,
        isGetterVisibility = JsonAutoDetect.Visibility.NONE)
@JsonPropertyOrder({ "pits", "playerPitCount", "initialStoneCountInPits" })
public class Board {
    private static final int BANK_COUNT = 2;

    private final List<Pit> pits;
    private final int playerPitCount;
    private final int initialStoneCountInPits;

    @JsonIgnore
    IntConsumer onGameMoveStart = index -> { };
    @JsonIgnore
    IntConsumer onGameMove = index -> { };
    @JsonIgnore
    IntConsumer onGameMoveEnd = index -> { };

    public Board(int playerPitCount, int initialStoneCountInPits) {
        this(playerPitCount, initialStoneCountInPits, null);
    }

    public Board(int playerPitCount, int initialStoneCountInPits, List<Pit> pits) {
        this.playerPitCount = playerPitCount;
        this.initialStoneCountInPits = initialStoneCountInPits;
        this.pits = pits != null ? pits : createPits(initialStoneCountInPits);
    }

    private List<Pit> createPits(int initialStoneCountInPits) {
        List<Pit> pitList = new ArrayList<>(playerPitCount * 2 + BANK_COUNT);
        for (int index = 0; index < totalPitCount(); index++) {
            PitType pitType = getPitTypeByIndex(index);
            pitList.add(pitType.isBank() ? new Bank(index, 0) : new Pit(index, initialStoneCountInPits));
        }
        return pitList;
    }

    public List<Pit> getPits() {
        return pits;
    }

    public int getPlayerPitCount() {
        return playerPitCount;
    }

    public int getInitialStoneCountInPits() {
        return initialStoneCountInPits;
    }

    public int player1PitStartIndex() {
        return 0;
    }

    public int player1PitStopIndex() {
        return player1PitStartIndex() + playerPitCount - 1;
    }

    public int player1BankIndex() {
        return player1PitStopIndex() + 1;
    }

    public int player2PitStartIndex() {
        return player1BankIndex() + 1;
    }

    public int player2PitStopIndex() {
        return player2PitStartIndex() + playerPitCount - 1;
    }

    public int player2BankIndex() {
        return player2PitStopIndex() + 1;
    }

    public int totalPitCount() {
        return player2BankIndex() + 1;
    }

    public boolean checkIndex(int index) {
        return index >= player1PitStartIndex() && index <= player2BankIndex();
    }

    void checkIndexAndMaybeThrowError(int index) {
        if (!checkIndex(index)) {
            throw new IllegalStateException("IndexOutOfRange => index : " + index + " [start, stop] = ["
                    + player1PitStartIndex() + ", " + player2BankIndex() + "]");
        }
    }

    public PitType getPitTypeByIndex(int index) {
        checkIndexAndMaybeThrowError(index);
        if (index >= player1PitStartIndex() && index <= player1PitStopIndex()) {
            return PitType.PLAYER1_PIT;
        } else if (index == player1BankIndex()) {
            return PitType.PLAYER1_BANK;
        } else if (index <= player2PitStopIndex()) {
            return PitType.PLAYER2_PIT;
        } else {
            return PitType.PLAYER2_BANK;
        }
    }

    public boolean checkPitTypeIsNormalPitByIndex(int index) {
        return getPitTypeByIndex(index).isNormalPit();
    }

    public boolean checkPitTypeIsBankByIndex(int index) {
        return getPitTypeByIndex(index).isBank();
    }

    public void move(int index) {
        checkIndexAndMaybeThrowError(index);
        PitType pitType = getPitTypeByIndex(index);
        if (pitType.isBank()) {
            throw new IllegalStateException("InCorrectPit => index : " + index + " pitType = " + pitTypeName(pitType));
        }
        Pit pit = pits.get(index);
        if (pit.getStoneCount() <= 0) {
            throw new IllegalStateException("StoneNotFound => index : " + index + " stoneCount = " + pit.getStoneCount());
        }
        List<Integer> path = getSowingPath(index);
        pit.setStoneCount(0);
        onGameMoveStart.accept(path.getFirst());
        path.forEach(this::onGameMoveStep);
        onGameMoveEnd.accept(path.getLast());
    }

    public List<Integer> getSowingPath(int index) {
        return getSowingPath(index, pits.get(index).getStoneCount());
    }

    // Indexes the stones of the pit are dropped into, in order. A single stone goes to the next pit; otherwise the
    // first stone goes back into the played pit. The player's own bank gets a stone, the opponent's bank is skipped.
    // The last index is where the last stone lands. Empty for a bank or an empty pit.
    public List<Integer> getSowingPath(int index, int stoneCount) {
        checkIndexAndMaybeThrowError(index);
        if (stoneCount <= 0 || checkPitTypeIsBankByIndex(index)) return List.of();
        int opponentBankIndex = getPitTypeByIndex(index) == PitType.PLAYER1_PIT ? player2BankIndex() : player1BankIndex();
        List<Integer> path = new ArrayList<>(stoneCount);
        int current = stoneCount == 1 ? getNextPitIndexCircularly(index) : index;
        while (path.size() < stoneCount) {
            if (current != opponentBankIndex) path.add(current);
            current = getNextPitIndexCircularly(current);
        }
        return path;
    }

    public void onGameMoveStep(int index) {
        pits.get(getPitIndexCircularly(index)).increaseStone();
        onGameMove.accept(index);
    }

    public int getNextPitIndexCircularly(int currentPitIndex) {
        checkIndexAndMaybeThrowError(currentPitIndex);
        return getPitIndexCircularly(currentPitIndex + 1);
    }

    public Pit getPitCircularly(int currentPitIndex) {
        return pits.get(getPitIndexCircularly(currentPitIndex));
    }

    public int getPitIndexCircularly(int currentPitIndex) {
        return currentPitIndex % totalPitCount();
    }

    public int[] getStoneArray() {
        return pits.stream().mapToInt(Pit::getStoneCount).toArray();
    }

    public List<Pit> player1Pits() {
        return pits.subList(player1PitStartIndex(), player1BankIndex());
    }

    public List<Pit> player2Pits() {
        return pits.subList(player2PitStartIndex(), player2BankIndex());
    }

    public Pit player1Bank() {
        return pits.get(player1BankIndex());
    }

    public Pit player2Bank() {
        return pits.get(player2BankIndex());
    }

    public int getOppositePitIndex(int index) {
        if (index > player1BankIndex()) {
            return player2PitStopIndex() - index;
        } else {
            return player1BankIndex() + playerPitCount - index;
        }
    }

    public void clearPlayer1Pits() {
        player1Pits().forEach(pit -> pit.setStoneCount(0));
    }

    public void clearPlayer2Pits() {
        player2Pits().forEach(pit -> pit.setStoneCount(0));
    }

    // The TypeScript name of a pit type, for error messages.
    static String pitTypeName(PitType pitType) {
        return switch (pitType) {
            case PLAYER1_PIT -> "player1Pit";
            case PLAYER1_BANK -> "player1Bank";
            case PLAYER2_PIT -> "player2Pit";
            case PLAYER2_BANK -> "player2Bank";
        };
    }
}