mancala/apps/backend/src/main/java/app/playmancala/game/GameManager.java

package app.playmancala.game;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadLocalRandom;
import java.util.function.LongSupplier;

import org.jboss.logging.Logger;

import com.fasterxml.jackson.databind.JsonNode;

import app.playmancala.engine.CommonMancalaGame;
import app.playmancala.engine.GameState;
import app.playmancala.engine.MancalaGame;
import app.playmancala.game.GameSerialization.GameEnding;
import app.playmancala.game.GameSerialization.LiveGameSnapshot;
import app.playmancala.live.LiveGameStore;
import app.playmancala.model.AuthUser;
import app.playmancala.model.Channels;
import app.playmancala.model.ClientGame;
import app.playmancala.model.EndReason;
import app.playmancala.model.GameEndMessage;
import app.playmancala.model.GameRecord;
import app.playmancala.model.GameUsersConnectionInfo;
import app.playmancala.model.PlayerSummary;
import app.playmancala.model.Seat;
import app.playmancala.model.UserConnectionInfo;
import app.playmancala.rtmt.Rtmt;

// Runs live games: matchmaking, moves, the clock, spectators and every way a game ends. Only touched on the game loop.
// Writes to Valkey go through `storeExecutor`, saving finished games through the recorder; neither blocks the loop.
public class GameManager {
    private static final Logger LOG = Logger.getLogger(GameManager.class);

    private final GameStore gameStore;
    private final Rtmt rtmt;
    private final MatchMaker matchMaker;
    private final LiveGameStore liveGameStore;
    private final GameRecorder recorder;
    private final Executor storeExecutor;
    private final LongSupplier clock;
    // Time each player has for a new game.
    private final long gameClockMs;
    private final List<Runnable> liveGamesListeners = new ArrayList<>();

    public GameManager(GameStore gameStore, Rtmt rtmt, MatchMaker matchMaker, LiveGameStore liveGameStore,
            GameRecorder recorder, Executor storeExecutor, LongSupplier clock, long gameClockMs) {
        this.gameStore = gameStore;
        this.rtmt = rtmt;
        this.matchMaker = matchMaker;
        this.liveGameStore = liveGameStore;
        this.recorder = recorder;
        this.storeExecutor = storeExecutor;
        this.clock = clock;
        this.gameClockMs = gameClockMs;
        matchMaker.listenOnPlayersPaired((player1Id, player2Id) -> startGame(createMancalaGame(player1Id, player2Id)));
        listenRtmtMessages();
        listenUserConnectionChange();
    }

    // Called whenever a live game starts, changes or ends.
    public void onLiveGamesChanged(Runnable listener) {
        liveGamesListeners.add(listener);
    }

    private void listenRtmtMessages() {
        rtmt.listenMessage(Channels.NEW_GAME, (userId, message) -> {
            BackendGame activeGame = gameStore.getGameByUser(userId);
            if (activeGame != null) {
                rtmt.sendMessage(userId, Channels.ON_NEW_GAME_REJECTED, Map.of("gameId", activeGame.id));
                return;
            }
            matchMaker.join(userId);
        });
        rtmt.listenMessage(Channels.CANCEL_NEW_GAME, (userId, message) -> matchMaker.cancel(userId));
        rtmt.listenMessage(Channels.GAME_MOVE, this::onGameMove);
        rtmt.listenMessage(Channels.LEAVE_GAME, (userId, message) -> onPlayerLeave(userId));
        rtmt.listenMessage(Channels.LISTEN_GAME_EVENTS, (userId, message) -> {
            if (message.isTextual()) addSpectator(userId, message.asText());
        });
        rtmt.listenMessage(Channels.UNLISTEN_GAME_EVENTS, (userId, message) -> {
            if (message.isTextual()) removeSpectator(userId, message.asText());
        });
    }

    private void onGameMove(String userId, JsonNode gameMove) {
        BackendGame game = gameStore.getGameByUser(userId);
        if (game == null) {
            LOG.debug("Game not found!");
            return;
        }
        MancalaGame mancalaGame = game.mancalaGame;
        try {
            long now = clock.getAsLong();
            // A move that arrives after the mover's time has run out is not played.
            if (userId.equals(mancalaGame.getTurnPlayerId()) && isOutOfTime(game, now)) {
                endGameOnTime(game);
                return;
            }
            JsonNode index = gameMove.path("index");
            if (!index.canConvertToInt() || !index.isIntegralNumber()) {
                throw new IllegalStateException("Invalid move: " + gameMove);
            }
            int movesBefore = mancalaGame.getHistory().size();
            Seat moverSeat = seatOf(mancalaGame, userId);
            mancalaGame.moveByPlayerPit(userId, index.asInt());
            if (mancalaGame.getHistory().size() > movesBefore && moverSeat != null) {
                game.moveTimes.add(now);
                GameClocks.ChargedMove charged = GameClocks.chargeMove(game.clock, moverSeat, now);
                game.clock = charged.clock();
                game.moveRemainingMs.add(charged.remainingMs());
            }
            game.gameUsersConnectionInfo = getGameUsersConnectionInfo(game);
            sendMessageToPlayersAndSpectators(game, Channels.ON_GAME_UPDATE, toClientGame(game));
            if (mancalaGame.getState() == GameState.ENDED) {
                endGame(game, new GameEnding(EndReason.COMPLETED, mancalaGame.getWonPlayerId(), null));
            } else {
                saveLiveGame(game);
                notifyLiveGamesChanged();
            }
        } catch (RuntimeException e) {
            onGameError(game, e);
        }
    }

    private void onGameError(BackendGame game, RuntimeException error) {
        LOG.error("(GameManager) Game " + game.id + " failed", error);
        String crash = CrashLog.describe(error, game);
        String fileName = CrashLog.fileName(game.id);
        storeExecutor.execute(() -> CrashLog.write(fileName, crash));
        LOG.infof("Game crash saved to file : %s", fileName);
        // The Node backend sent the Error object, which serialises to {}; clients only use the channel.
        sendMessageToPlayersAndSpectators(game, Channels.ON_GAME_CRASHED, Map.of());
    }

    private void onPlayerLeave(String userId) {
        BackendGame game = gameStore.getGameByUser(userId);
        if (game != null) {
            endGame(game, new GameEnding(EndReason.LEFT, game.opponentOf(userId), userId));
        }
    }

    // Ends a live game for any reason: stops the clock, tells everyone, forgets the game and saves it.
    private void endGame(BackendGame game, GameEnding ending) {
        if (gameStore.get(game.id) != game) return;
        deleteGame(game);
        game.clock = GameClocks.stop(game.clock, getRunningSeat(game), clock.getAsLong());
        GameEndMessage endMessage = new GameEndMessage(game.id, GameSerialization.getResult(game, ending),
                ending.endReason(), game.clock, ending.winnerId(), ending.leftUserId());
        if (ending.leftUserId() != null) {
            sendMessageToPlayersAndSpectators(game, Channels.ON_GAME_USER_LEAVE, ending.leftUserId());
        }
        sendMessageToPlayersAndSpectators(game, Channels.ON_GAME_END, endMessage);
        game.spectatorIds.clear();

        GameRecord record = GameSerialization.toGameRecord(game, ending, clock.getAsLong());
        inStore(() -> liveGameStore.removeGame(game.id));
        recorder.save(record);
        notifyLiveGamesChanged();
    }

    // The player whose turn it is ran out of time: the opponent wins.
    private void endGameOnTime(BackendGame game) {
        endGame(game, new GameEnding(EndReason.TIMEOUT, game.opponentOf(game.mancalaGame.getTurnPlayerId()), null));
    }

    private boolean isOutOfTime(BackendGame game, long now) {
        Seat runningSeat = getRunningSeat(game);
        return runningSeat != null && GameClocks.getRemainingMs(game.clock, runningSeat, runningSeat, now) <= 0;
    }

    // The seat whose clock runs; null once the game has ended.
    private Seat getRunningSeat(BackendGame game) {
        MancalaGame mancalaGame = game.mancalaGame;
        if (mancalaGame.getState() == GameState.ENDED || game.clock.turnStartedAt() == null) return null;
        return seatOf(mancalaGame, mancalaGame.getTurnPlayerId());
    }

    private static Seat seatOf(MancalaGame mancalaGame, String playerId) {
        return GameClocks.getSeat(mancalaGame.getPlayer1Id(), mancalaGame.getPlayer2Id(), playerId);
    }

    // Ends every live game whose running clock has reached zero; run by GameClockScheduler. The clock runs whether or
    // not the players are online, so this also ends games that both players have left.
    public void endGamesOutOfTime() {
        long now = clock.getAsLong();
        for (BackendGame game : gameStore.getAll()) {
            try {
                if (isOutOfTime(game, now)) endGameOnTime(game);
            } catch (RuntimeException e) {
                LOG.error("(GameManager) Could not end game " + game.id + " on time", e);
            }
        }
    }

    // Puts the live games saved in Valkey back into memory, e.g. after a restart or deploy. Blocks on Valkey and the
    // database; runs once at startup.
    public int restoreLiveGames() {
        List<JsonNode> stored;
        try {
            stored = liveGameStore.loadGames();
        } catch (RuntimeException e) {
            LOG.errorf("(GameManager) Could not load live games: %s", e.getMessage());
            return 0;
        }
        int restored = 0;
        for (JsonNode json : stored) {
            LiveGameSnapshot snapshot = GameSerialization.parseSnapshot(json);
            if (snapshot == null || gameStore.get(snapshot.id()) != null) continue;
            // A game that ended but whose snapshot could not be removed must not come back.
            if (isRecorded(snapshot.id())) {
                inStore(() -> liveGameStore.removeGame(snapshot.id()));
                continue;
            }
            BackendGame game = GameSerialization.fromSnapshot(snapshot, clock.getAsLong(), gameClockMs);
            gameStore.set(game.id, game);
            gameStore.setGameByUser(game.mancalaGame.getPlayer1Id(), game);
            gameStore.setGameByUser(game.mancalaGame.getPlayer2Id(), game);
            game.gameUsersConnectionInfo = getGameUsersConnectionInfo(game);
            restored++;
        }
        if (restored > 0) {
            LOG.infof("(GameManager) Restored %d live game(s)", restored);
            notifyLiveGamesChanged();
        }
        return restored;
    }

    private boolean isRecorded(String gameId) {
        try {
            return recorder.isRecorded(gameId);
        } catch (RuntimeException e) {
            return false;
        }
    }

    private void addSpectator(String userId, String gameId) {
        BackendGame game = gameStore.get(gameId);
        if (game == null || game.isPlayer(userId) || game.spectatorIds.contains(userId)) return;
        game.spectatorIds.add(userId);
        if (!game.allSpectatorIds.contains(userId)) game.allSpectatorIds.add(userId);
        game.peakSpectators = Math.max(game.peakSpectators, game.spectatorIds.size());
        saveLiveGame(game);
        notifyLiveGamesChanged();
    }

    private void removeSpectator(String userId, String gameId) {
        BackendGame game = gameStore.get(gameId);
        if (game != null && game.spectatorIds.remove(userId)) {
            notifyLiveGamesChanged();
        }
    }

    private void sendMessageToPlayersAndSpectators(BackendGame game, String channel, Object message) {
        rtmt.sendMessage(game.mancalaGame.getPlayer1Id(), channel, message);
        rtmt.sendMessage(game.mancalaGame.getPlayer2Id(), channel, message);
        List.copyOf(game.spectatorIds).forEach(spectatorId -> rtmt.sendMessage(spectatorId, channel, message));
    }

    public ClientGame toClientGame(BackendGame game) {
        return new ClientGame(game.id, game.mancalaGame, game.gameUsersConnectionInfo, game.startedAt,
                List.copyOf(game.moveTimes), game.spectatorIds.size(), game.clock, clock.getAsLong());
    }

    public BackendGame createMancalaGame(String userId1, String userId2) {
        MancalaGame mancalaGame = new CommonMancalaGame(UUID.randomUUID().toString(), userId1, userId2);
        mancalaGame.setTurnPlayerId(ThreadLocalRandom.current().nextBoolean() ? userId1 : userId2);
        long now = clock.getAsLong();
        PlayerSummary player1 = getPlayerInfo(userId1);
        PlayerSummary player2 = getPlayerInfo(userId2);
        Map<String, PlayerSummary> players = new LinkedHashMap<>();
        players.put(userId1, player1);
        players.put(userId2, player2);
        BackendGame game = new BackendGame(mancalaGame, getGameUsersConnectionInfo(player1, player2), List.of(), 0,
                players, now, List.of(), GameClocks.start(gameClockMs, now), List.of());
        gameStore.set(game.id, game);
        gameStore.setGameByUser(userId1, game);
        gameStore.setGameByUser(userId2, game);
        return game;
    }

    private PlayerSummary getPlayerInfo(String userId) {
        AuthUser user = rtmt.getUser(userId);
        return new PlayerSummary(userId, user != null ? user.name() : null, user == null || user.isGuest());
    }

    public GameUsersConnectionInfo getGameUsersConnectionInfo(BackendGame game) {
        return getGameUsersConnectionInfo(game.player(game.mancalaGame.getPlayer1Id()),
                game.player(game.mancalaGame.getPlayer2Id()));
    }

    private GameUsersConnectionInfo getGameUsersConnectionInfo(PlayerSummary player1, PlayerSummary player2) {
        return new GameUsersConnectionInfo(
                UserConnectionInfo.of(player1, rtmt.isClientOnline(player1.userId())),
                UserConnectionInfo.of(player2, rtmt.isClientOnline(player2.userId())));
    }

    public void startGame(BackendGame game) {
        sendMessageToPlayersAndSpectators(game, Channels.ON_GAME_START, toClientGame(game));
        sendUserConnectionInfo(game);
        saveLiveGame(game);
        notifyLiveGamesChanged();
    }

    public void sendUserConnectionInfo(BackendGame game) {
        game.gameUsersConnectionInfo = getGameUsersConnectionInfo(game);
        sendMessageToPlayersAndSpectators(game, Channels.ON_USER_CONNECTION_CHANGE, game.gameUsersConnectionInfo);
    }

    public void deleteGame(BackendGame game) {
        gameStore.removeGameByPlayer(game.mancalaGame.getPlayer1Id());
        gameStore.removeGameByPlayer(game.mancalaGame.getPlayer2Id());
        gameStore.remove(game.id);
    }

    private void saveLiveGame(BackendGame game) {
        LiveGameSnapshot snapshot = GameSerialization.toSnapshot(game);
        inStore(() -> liveGameStore.saveGame(game.id, snapshot));
    }

    // Runs a Valkey write off the loop; a failure is only logged, the game goes on from memory.
    private void inStore(Runnable write) {
        storeExecutor.execute(() -> {
            try {
                write.run();
            } catch (RuntimeException e) {
                LOG.errorf("(GameManager) Live game store: %s", e.getMessage());
            }
        });
    }

    private void notifyLiveGamesChanged() {
        liveGamesListeners.forEach(Runnable::run);
    }

    private void listenUserConnectionChange() {
        rtmt.listenOnClientConnectionChange((clientId, isOnline) -> {
            BackendGame game = gameStore.getGameByUser(clientId);
            if (game != null) sendUserConnectionInfo(game);
            if (!isOnline) {
                gameStore.getSpectatingGameIdsByUser(clientId).forEach(gameId -> removeSpectator(clientId, gameId));
            } else if (game != null) {
                rtmt.sendMessage(clientId, Channels.ON_GAME_UPDATE, toClientGame(game));
            }
        });
    }
}