feat(state): add validated persistent game state

src/main/java/games/dmg/spigottyrant/Ability.java

@@ -0,0 +1,9 @@
+package games.dmg.spigottyrant;
+
+public enum Ability {
+    ASSASSIN_INVISIBILITY,
+    ASSASSIN_DOUBLE_JUMP,
+    FIXER_BOOST,
+    TAMER_CAPTURE,
+    ROSTER_INTELLIGENCE
+}

src/main/java/games/dmg/spigottyrant/CapturedMob.java

@@ -0,0 +1,14 @@
+package games.dmg.spigottyrant;
+
+import java.util.Locale;
+import java.util.Map;
+
+public record CapturedMob(String entityType, Map<String, String> data) {
+    public CapturedMob {
+        if (entityType == null || entityType.isBlank()) {
+            throw new IllegalArgumentException("entityType must not be blank");
+        }
+        entityType = entityType.trim().toUpperCase(Locale.ROOT);
+        data = data == null ? Map.of() : Map.copyOf(data);
+    }
+}

src/main/java/games/dmg/spigottyrant/GameLifecycle.java

@@ -0,0 +1,7 @@
+package games.dmg.spigottyrant;
+
+public enum GameLifecycle {
+    UNSTARTED,
+    RUNNING,
+    PAUSED
+}

src/main/java/games/dmg/spigottyrant/GameState.java

@@ -0,0 +1,59 @@
+package games.dmg.spigottyrant;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+
+public record GameState(
+    GameLifecycle lifecycle,
+    Optional<UUID> tyrantId,
+    Optional<UUID> vigilanteId,
+    Optional<PendingSelection> pendingTyrant,
+    Optional<PendingSelection> pendingVigilante,
+    Optional<Instant> pausedAt,
+    Duration accumulatedPausedTime,
+    int tyrantLevel,
+    int unspentChoices,
+    Set<TyrantUnlock> purchases
+) {
+    public GameState {
+        lifecycle = lifecycle == null ? GameLifecycle.UNSTARTED : lifecycle;
+        tyrantId = tyrantId == null ? Optional.empty() : tyrantId;
+        vigilanteId = vigilanteId == null ? Optional.empty() : vigilanteId;
+        pendingTyrant = pendingTyrant == null ? Optional.empty() : pendingTyrant;
+        pendingVigilante = pendingVigilante == null ? Optional.empty() : pendingVigilante;
+        pausedAt = pausedAt == null ? Optional.empty() : pausedAt;
+        accumulatedPausedTime = accumulatedPausedTime == null
+            ? Duration.ZERO : accumulatedPausedTime;
+        purchases = purchases == null ? Set.of() : Set.copyOf(purchases);
+        if (tyrantId.isPresent() && tyrantId.equals(vigilanteId)) {
+            throw new IllegalArgumentException("Tyrant and Vigilante must be different players");
+        }
+        if (tyrantLevel < 0 || unspentChoices < 0) {
+            throw new IllegalArgumentException("progression values must not be negative");
+        }
+        if (accumulatedPausedTime.isNegative()) {
+            throw new IllegalArgumentException("accumulated paused time must not be negative");
+        }
+        if ((lifecycle == GameLifecycle.PAUSED) != pausedAt.isPresent()) {
+            throw new IllegalArgumentException("pausedAt must be present exactly while paused");
+        }
+    }
+
+    public static GameState empty() {
+        return new GameState(
+            GameLifecycle.UNSTARTED,
+            Optional.empty(),
+            Optional.empty(),
+            Optional.empty(),
+            Optional.empty(),
+            Optional.empty(),
+            Duration.ZERO,
+            0,
+            0,
+            Set.of()
+        );
+    }
+}

src/main/java/games/dmg/spigottyrant/PauseAwareTime.java

@@ -0,0 +1,20 @@
+package games.dmg.spigottyrant;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Objects;
+
+public final class PauseAwareTime {
+    private PauseAwareTime() {
+    }
+
+    public static Instant shiftDeadline(Instant deadline, Instant pausedAt, Instant resumedAt) {
+        Objects.requireNonNull(deadline, "deadline");
+        Objects.requireNonNull(pausedAt, "pausedAt");
+        Objects.requireNonNull(resumedAt, "resumedAt");
+        if (resumedAt.isBefore(pausedAt)) {
+            throw new IllegalArgumentException("resumedAt must not precede pausedAt");
+        }
+        return deadline.plus(Duration.between(pausedAt, resumedAt));
+    }
+}

src/main/java/games/dmg/spigottyrant/PendingSelection.java

@@ -0,0 +1,12 @@
+package games.dmg.spigottyrant;
+
+import java.time.Instant;
+import java.util.Objects;
+import java.util.UUID;
+
+public record PendingSelection(UUID candidateId, Instant expiresAt) {
+    public PendingSelection {
+        Objects.requireNonNull(candidateId, "candidateId");
+        Objects.requireNonNull(expiresAt, "expiresAt");
+    }
+}

src/main/java/games/dmg/spigottyrant/PersistentState.java

@@ -0,0 +1,20 @@
+package games.dmg.spigottyrant;
+
+import java.util.Map;
+import java.util.UUID;
+
+public record PersistentState(GameState game, Map<UUID, PlayerState> players) {
+    public PersistentState {
+        game = game == null ? GameState.empty() : game;
+        players = players == null ? Map.of() : Map.copyOf(players);
+        for (Map.Entry<UUID, PlayerState> entry : players.entrySet()) {
+            if (!entry.getKey().equals(entry.getValue().playerId())) {
+                throw new IllegalArgumentException("player map key must match player state ID");
+            }
+        }
+    }
+
+    public static PersistentState empty() {
+        return new PersistentState(GameState.empty(), Map.of());
+    }
+}

src/main/java/games/dmg/spigottyrant/PlayerState.java

@@ -0,0 +1,51 @@
+package games.dmg.spigottyrant;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+
+public record PlayerState(
+    UUID playerId,
+    String latestName,
+    Optional<Instant> lastLogin,
+    Optional<Instant> optedOutUntil,
+    TyrantClass tyrantClass,
+    Optional<UUID> followerOf,
+    Map<Ability, Instant> cooldownEnds,
+    Set<Ability> readyAbilityItems,
+    List<CapturedMob> capturedMobs
+) {
+    public PlayerState {
+        if (playerId == null) {
+            throw new IllegalArgumentException("playerId must not be null");
+        }
+        if (latestName == null || latestName.isBlank()) {
+            throw new IllegalArgumentException("latestName must not be blank");
+        }
+        latestName = latestName.trim();
+        lastLogin = lastLogin == null ? Optional.empty() : lastLogin;
+        optedOutUntil = optedOutUntil == null ? Optional.empty() : optedOutUntil;
+        tyrantClass = tyrantClass == null ? TyrantClass.NONE : tyrantClass;
+        followerOf = followerOf == null ? Optional.empty() : followerOf;
+        cooldownEnds = cooldownEnds == null ? Map.of() : Map.copyOf(cooldownEnds);
+        readyAbilityItems = readyAbilityItems == null ? Set.of() : Set.copyOf(readyAbilityItems);
+        capturedMobs = capturedMobs == null ? List.of() : List.copyOf(capturedMobs);
+    }
+
+    public static PlayerState newPlayer(UUID playerId, String latestName) {
+        return new PlayerState(
+            playerId,
+            latestName,
+            Optional.empty(),
+            Optional.empty(),
+            TyrantClass.NONE,
+            Optional.empty(),
+            Map.of(),
+            Set.of(),
+            List.of()
+        );
+    }
+}

src/main/java/games/dmg/spigottyrant/PluginSettings.java

@@ -0,0 +1,266 @@
+package games.dmg.spigottyrant;
+
+import java.time.Duration;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+import org.bukkit.configuration.ConfigurationSection;
+
+public record PluginSettings(
+    double tyrantRangeBlocks,
+    double followerRangeBlocks,
+    Duration optOutDuration,
+    Duration roleInactivity,
+    Duration candidateActivityWindow,
+    Duration pendingSelectionTimeout,
+    Duration selectionRetryInterval,
+    Duration assassinCooldown,
+    Duration assassinInvisibilityDuration,
+    Duration assassinDoubleJumpCooldown,
+    Duration assassinSpeedDuration,
+    Duration assassinWeaknessDuration,
+    int assassinWeaknessLevel,
+    Duration fixerCooldown,
+    Duration fixerEffectDuration,
+    int fixerStrengthLevel,
+    int fixerNormalHeartRows,
+    int fixerNearTyrantHeartRows,
+    Duration rosterIntelligenceCooldown,
+    int tyrantStrengthLevel,
+    int tyrantResistanceLevel,
+    int followerStrengthCap,
+    int followerResistanceCap,
+    Set<String> deniedMobTypes,
+    AbilityItemSettings assassinItem,
+    AbilityItemSettings fixerItem,
+    AbilityItemSettings tamerItem,
+    String recoveryCommand,
+    String inventoryFullMessage,
+    boolean freezeTimersWhilePaused
+) {
+    public PluginSettings {
+        requirePositiveFinite(tyrantRangeBlocks, "tyrant-range-blocks");
+        requirePositiveFinite(followerRangeBlocks, "follower-range-blocks");
+        requirePositive(optOutDuration, "opt-out-seconds");
+        requirePositive(roleInactivity, "role-inactivity-seconds");
+        requirePositive(candidateActivityWindow, "candidate-activity-window-seconds");
+        requirePositive(pendingSelectionTimeout, "pending-selection-timeout-seconds");
+        requirePositive(selectionRetryInterval, "selection-retry-seconds");
+        requirePositive(assassinCooldown, "assassin-cooldown-seconds");
+        requirePositive(assassinInvisibilityDuration, "assassin-invisibility-seconds");
+        requirePositive(assassinDoubleJumpCooldown, "assassin-double-jump-cooldown-seconds");
+        requirePositive(assassinSpeedDuration, "assassin-speed-seconds");
+        requirePositive(assassinWeaknessDuration, "assassin-weakness-seconds");
+        requireEffectLevel(assassinWeaknessLevel, "assassin-weakness-level");
+        requirePositive(fixerCooldown, "fixer-cooldown-seconds");
+        requirePositive(fixerEffectDuration, "fixer-effect-seconds");
+        requireEffectLevel(fixerStrengthLevel, "fixer-strength-level");
+        requireHeartRows(fixerNormalHeartRows, "fixer-normal-heart-rows");
+        requireHeartRows(fixerNearTyrantHeartRows, "fixer-near-tyrant-heart-rows");
+        if (fixerNearTyrantHeartRows < fixerNormalHeartRows) {
+            throw new IllegalArgumentException(
+                "fixer-near-tyrant-heart-rows must be at least fixer-normal-heart-rows"
+            );
+        }
+        requirePositive(rosterIntelligenceCooldown, "roster-intelligence-cooldown-seconds");
+        requireEffectLevel(tyrantStrengthLevel, "tyrant-strength-level");
+        requireEffectLevel(tyrantResistanceLevel, "tyrant-resistance-level");
+        requireEffectLevel(followerStrengthCap, "follower-strength-cap");
+        requireEffectLevel(followerResistanceCap, "follower-resistance-cap");
+        deniedMobTypes = normalizedSet(deniedMobTypes, "denied-mob-types");
+        assassinItem = Objects.requireNonNull(assassinItem, "assassinItem");
+        fixerItem = Objects.requireNonNull(fixerItem, "fixerItem");
+        tamerItem = Objects.requireNonNull(tamerItem, "tamerItem");
+        recoveryCommand = requireText(recoveryCommand, "recovery-command");
+        inventoryFullMessage = requireText(inventoryFullMessage, "inventory-full-message");
+    }
+
+    public static PluginSettings from(Map<String, ?> values) {
+        Objects.requireNonNull(values, "values");
+        return new PluginSettings(
+            decimal(values, "tyrant-range-blocks", 50.0),
+            decimal(values, "follower-range-blocks", 50.0),
+            duration(values, "opt-out-seconds", Duration.ofDays(7)),
+            duration(values, "role-inactivity-seconds", Duration.ofHours(48)),
+            duration(values, "candidate-activity-window-seconds", Duration.ofHours(24)),
+            duration(values, "pending-selection-timeout-seconds", Duration.ofHours(24)),
+            duration(values, "selection-retry-seconds", Duration.ofMinutes(1)),
+            duration(values, "assassin-cooldown-seconds", Duration.ofHours(1)),
+            duration(values, "assassin-invisibility-seconds", Duration.ofMinutes(10)),
+            duration(values, "assassin-double-jump-cooldown-seconds", Duration.ofSeconds(60)),
+            duration(values, "assassin-speed-seconds", Duration.ofSeconds(15)),
+            duration(values, "assassin-weakness-seconds", Duration.ofSeconds(20)),
+            integer(values, "assassin-weakness-level", 3),
+            duration(values, "fixer-cooldown-seconds", Duration.ofHours(1)),
+            duration(values, "fixer-effect-seconds", Duration.ofMinutes(10)),
+            integer(values, "fixer-strength-level", 1),
+            integer(values, "fixer-normal-heart-rows", 2),
+            integer(values, "fixer-near-tyrant-heart-rows", 3),
+            duration(values, "roster-intelligence-cooldown-seconds", Duration.ofHours(24)),
+            integer(values, "tyrant-strength-level", 1),
+            integer(values, "tyrant-resistance-level", 1),
+            integer(values, "follower-strength-cap", 5),
+            integer(values, "follower-resistance-cap", 4),
+            stringSet(values, "denied-mob-types", Set.of("ENDER_DRAGON", "WITHER")),
+            item(values, "assassin-item", new AbilityItemSettings("STICK", "Assassin Cloak")),
+            item(values, "fixer-item", new AbilityItemSettings("STICK", "Fixer's Wrench")),
+            item(values, "tamer-item", new AbilityItemSettings("FISHING_ROD", "Tamer's Lead")),
+            string(values, "recovery-command", "/tyrant item"),
+            string(
+                values,
+                "inventory-full-message",
+                "Your inventory is full. Make room and use /tyrant item."
+            ),
+            bool(values, "freeze-timers-while-paused", true)
+        );
+    }
+
+    private static AbilityItemSettings item(
+        Map<String, ?> values,
+        String key,
+        AbilityItemSettings defaultValue
+    ) {
+        Object raw = values.get(key);
+        if (raw == null) {
+            return defaultValue;
+        }
+        Map<?, ?> map;
+        if (raw instanceof ConfigurationSection section) {
+            map = section.getValues(false);
+        } else if (raw instanceof Map<?, ?> itemValues) {
+            map = itemValues;
+        } else {
+            throw new IllegalArgumentException(key + " must be a section");
+        }
+        Object material = map.get("material");
+        Object name = map.get("name");
+        return new AbilityItemSettings(
+            material == null ? defaultValue.material() : material.toString(),
+            name == null ? defaultValue.name() : name.toString()
+        );
+    }
+
+    private static double decimal(Map<String, ?> values, String key, double defaultValue) {
+        Object raw = values.get(key);
+        if (raw == null) {
+            return defaultValue;
+        }
+        if (!(raw instanceof Number number)) {
+            throw new IllegalArgumentException(key + " must be numeric");
+        }
+        return number.doubleValue();
+    }
+
+    private static int integer(Map<String, ?> values, String key, int defaultValue) {
+        Object raw = values.get(key);
+        if (raw == null) {
+            return defaultValue;
+        }
+        if (!(raw instanceof Number number)) {
+            throw new IllegalArgumentException(key + " must be an integer");
+        }
+        double value = number.doubleValue();
+        if (!Double.isFinite(value) || value != Math.rint(value)
+                || value < Integer.MIN_VALUE || value > Integer.MAX_VALUE) {
+            throw new IllegalArgumentException(key + " must be a 32-bit integer");
+        }
+        return number.intValue();
+    }
+
+    private static String string(Map<String, ?> values, String key, String defaultValue) {
+        Object raw = values.get(key);
+        return raw == null ? defaultValue : raw.toString();
+    }
+
+    private static boolean bool(Map<String, ?> values, String key, boolean defaultValue) {
+        Object raw = values.get(key);
+        if (raw == null) {
+            return defaultValue;
+        }
+        if (!(raw instanceof Boolean value)) {
+            throw new IllegalArgumentException(key + " must be true or false");
+        }
+        return value;
+    }
+
+    private static Set<String> stringSet(
+        Map<String, ?> values,
+        String key,
+        Set<String> defaultValue
+    ) {
+        Object raw = values.get(key);
+        if (raw == null) {
+            return defaultValue;
+        }
+        if (!(raw instanceof List<?> list)) {
+            throw new IllegalArgumentException(key + " must be a list");
+        }
+        return list.stream().map(Object::toString).collect(Collectors.toUnmodifiableSet());
+    }
+
+    private static void requirePositiveFinite(double value, String key) {
+        if (!Double.isFinite(value) || value <= 0.0) {
+            throw new IllegalArgumentException(key + " must be positive and finite");
+        }
+    }
+
+    private static void requirePositive(Duration value, String key) {
+        Objects.requireNonNull(value, key);
+        if (value.isZero() || value.isNegative()) {
+            throw new IllegalArgumentException(key + " must be positive");
+        }
+    }
+
+    private static void requireEffectLevel(int value, String key) {
+        if (value < 1 || value > 255) {
+            throw new IllegalArgumentException(key + " must be between 1 and 255");
+        }
+    }
+
+    private static void requireHeartRows(int value, String key) {
+        if (value < 1 || value > 100) {
+            throw new IllegalArgumentException(key + " must be between 1 and 100");
+        }
+    }
+
+    private static Set<String> normalizedSet(Set<String> values, String key) {
+        if (values == null || values.isEmpty()) {
+            throw new IllegalArgumentException(key + " must not be empty");
+        }
+        return values.stream()
+            .map(value -> requireText(value, key).toUpperCase(Locale.ROOT))
+            .collect(Collectors.toUnmodifiableSet());
+    }
+
+    private static String requireText(String value, String key) {
+        if (value == null || value.isBlank()) {
+            throw new IllegalArgumentException(key + " must not be blank");
+        }
+        return value.trim();
+    }
+
+    private static Duration duration(Map<String, ?> values, String key, Duration defaultValue) {
+        Object raw = values.get(key);
+        if (raw == null) {
+            return defaultValue;
+        }
+        if (!(raw instanceof Number number)) {
+            throw new IllegalArgumentException(key + " must be an integer number of seconds");
+        }
+        double seconds = number.doubleValue();
+        if (!Double.isFinite(seconds) || seconds != Math.rint(seconds)) {
+            throw new IllegalArgumentException(key + " must be an integer number of seconds");
+        }
+        return Duration.ofSeconds(number.longValue());
+    }
+
+    public record AbilityItemSettings(String material, String name) {
+        public AbilityItemSettings {
+            material = requireText(material, "item material").toUpperCase(Locale.ROOT);
+            name = requireText(name, "item name");
+        }
+    }
+}

src/main/java/games/dmg/spigottyrant/PluginSettingsValidator.java

@@ -0,0 +1,36 @@
+package games.dmg.spigottyrant;
+
+import org.bukkit.Material;
+import org.bukkit.entity.EntityType;
+
+public final class PluginSettingsValidator {
+    private PluginSettingsValidator() {
+    }
+
+    public static PluginSettings validate(PluginSettings settings) {
+        validateItem(settings.assassinItem(), "assassin-item");
+        validateItem(settings.fixerItem(), "fixer-item");
+        validateItem(settings.tamerItem(), "tamer-item");
+        for (String entityType : settings.deniedMobTypes()) {
+            try {
+                EntityType.valueOf(entityType);
+            } catch (IllegalArgumentException exception) {
+                throw new IllegalArgumentException(
+                    entityType + " in denied-mob-types is not a known entity type",
+                    exception
+                );
+            }
+        }
+        if (!settings.deniedMobTypes().contains("ENDER_DRAGON")) {
+            throw new IllegalArgumentException("denied-mob-types must include ENDER_DRAGON");
+        }
+        return settings;
+    }
+
+    private static void validateItem(PluginSettings.AbilityItemSettings item, String key) {
+        Material material = Material.matchMaterial(item.material());
+        if (material == null || material == Material.AIR) {
+            throw new IllegalArgumentException(key + " material must identify an item");
+        }
+    }
+}

src/main/java/games/dmg/spigottyrant/SpigotTyrantPlugin.java

@@ -1,10 +1,52 @@
 package games.dmg.spigottyrant;
 
+import java.io.IOException;
+import java.util.Map;
+import java.util.logging.Level;
 import org.bukkit.plugin.java.JavaPlugin;
 
 public final class SpigotTyrantPlugin extends JavaPlugin {
+    private PluginSettings settings;
+    private TyrantStateManager stateManager;
+
     @Override
     public void onEnable() {
+        saveDefaultConfig();
+        try {
+            Map<String, Object> values = getConfig().getValues(false);
+            settings = PluginSettingsValidator.validate(PluginSettings.from(values));
+            stateManager = new TyrantStateManager(
+                new YamlTyrantStateRepository(getDataFolder().toPath().resolve("state.yml")),
+                getLogger()
+            );
+        } catch (IllegalArgumentException | IOException exception) {
+            getLogger().log(Level.SEVERE, "Could not initialize Spigot Tyrant", exception);
+            getServer().getPluginManager().disablePlugin(this);
+            return;
+        }
+
+        getServer().getScheduler().runTaskTimer(this, stateManager::saveIfDirty, 600L, 600L);
         getLogger().info("Spigot Tyrant enabled.");
     }
+
+    @Override
+    public void onDisable() {
+        if (stateManager != null) {
+            stateManager.saveIfDirty();
+        }
+    }
+
+    PluginSettings settings() {
+        if (settings == null) {
+            throw new IllegalStateException("Plugin settings are unavailable");
+        }
+        return settings;
+    }
+
+    TyrantStateManager stateManager() {
+        if (stateManager == null) {
+            throw new IllegalStateException("State manager is unavailable");
+        }
+        return stateManager;
+    }
 }

src/main/java/games/dmg/spigottyrant/TyrantClass.java

@@ -0,0 +1,8 @@
+package games.dmg.spigottyrant;
+
+public enum TyrantClass {
+    NONE,
+    ASSASSIN,
+    FIXER,
+    TAMER
+}

src/main/java/games/dmg/spigottyrant/TyrantStateManager.java

@@ -0,0 +1,100 @@
+package games.dmg.spigottyrant;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.util.function.UnaryOperator;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public final class TyrantStateManager {
+    private final YamlTyrantStateRepository repository;
+    private final Logger logger;
+    private final Map<UUID, PlayerState> players;
+    private GameState game;
+    private boolean dirty;
+
+    public TyrantStateManager(
+        YamlTyrantStateRepository repository,
+        Logger logger
+    ) throws IOException {
+        this.repository = repository;
+        this.logger = logger;
+        PersistentState state = repository.load();
+        game = state.game();
+        players = new HashMap<>(state.players());
+    }
+
+    public GameState game() {
+        return game;
+    }
+
+    public Map<UUID, PlayerState> players() {
+        return Map.copyOf(players);
+    }
+
+    public PlayerState player(UUID playerId, String latestName) {
+        PlayerState current = players.get(playerId);
+        if (current == null) {
+            current = PlayerState.newPlayer(playerId, latestName);
+            players.put(playerId, current);
+            dirty = true;
+            return current;
+        }
+        if (!current.latestName().equals(latestName)) {
+            current = copyWithName(current, latestName);
+            players.put(playerId, current);
+            dirty = true;
+        }
+        return current;
+    }
+
+    public PlayerState updatePlayer(
+        UUID playerId,
+        String latestName,
+        UnaryOperator<PlayerState> update
+    ) {
+        PlayerState changed = update.apply(player(playerId, latestName));
+        if (!playerId.equals(changed.playerId())) {
+            throw new IllegalArgumentException("updated player ID cannot change");
+        }
+        players.put(playerId, changed);
+        dirty = true;
+        return changed;
+    }
+
+    public GameState updateGame(UnaryOperator<GameState> update) {
+        game = update.apply(game);
+        dirty = true;
+        return game;
+    }
+
+    public boolean saveIfDirty() {
+        if (!dirty) {
+            return true;
+        }
+        try {
+            repository.save(new PersistentState(game, players));
+            dirty = false;
+            return true;
+        } catch (IOException exception) {
+            logger.log(Level.SEVERE, "Could not save Spigot Tyrant state", exception);
+            return false;
+        }
+    }
+
+    private static PlayerState copyWithName(PlayerState player, String latestName) {
+        return new PlayerState(
+            player.playerId(),
+            latestName,
+            player.lastLogin(),
+            player.optedOutUntil(),
+            player.tyrantClass(),
+            player.followerOf(),
+            player.cooldownEnds(),
+            player.readyAbilityItems(),
+            player.capturedMobs()
+        );
+    }
+}

src/main/java/games/dmg/spigottyrant/TyrantUnlock.java

@@ -0,0 +1,10 @@
+package games.dmg.spigottyrant;
+
+public enum TyrantUnlock {
+    ASSASSIN,
+    FIXER,
+    TAMER,
+    ROSTER_INTELLIGENCE,
+    RESISTANCE,
+    STRENGTH
+}

src/main/java/games/dmg/spigottyrant/YamlTyrantStateRepository.java

@@ -0,0 +1,335 @@
+package games.dmg.spigottyrant;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.format.DateTimeParseException;
+import java.util.ArrayList;
+import java.util.EnumMap;
+import java.util.EnumSet;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+import org.bukkit.configuration.ConfigurationSection;
+import org.bukkit.configuration.InvalidConfigurationException;
+import org.bukkit.configuration.file.YamlConfiguration;
+import org.bukkit.entity.EntityType;
+
+public final class YamlTyrantStateRepository {
+    private static final String PLAYERS = "players";
+    private final Path stateFile;
+
+    public YamlTyrantStateRepository(Path stateFile) {
+        this.stateFile = stateFile;
+    }
+
+    public PersistentState load() throws IOException {
+        if (!Files.exists(stateFile)) {
+            return PersistentState.empty();
+        }
+        YamlConfiguration yaml = loadYaml();
+        return new PersistentState(loadGameSafely(yaml), loadPlayers(yaml));
+    }
+
+    public void save(PersistentState state) throws IOException {
+        Path parent = stateFile.toAbsolutePath().getParent();
+        if (parent != null) {
+            Files.createDirectories(parent);
+        }
+        YamlConfiguration yaml = Files.exists(stateFile) ? loadYaml() : new YamlConfiguration();
+        saveGame(yaml, state.game());
+        removeAbsentPlayers(yaml, state.players().keySet());
+        for (PlayerState player : state.players().values()) {
+            savePlayer(yaml, player);
+        }
+
+        Path temporary = Files.createTempFile(parent, "spigot-tyrant-state-", ".yml");
+        try {
+            yaml.save(temporary.toFile());
+            try {
+                Files.move(
+                    temporary,
+                    stateFile,
+                    StandardCopyOption.REPLACE_EXISTING,
+                    StandardCopyOption.ATOMIC_MOVE
+                );
+            } catch (IOException atomicMoveFailure) {
+                Files.move(temporary, stateFile, StandardCopyOption.REPLACE_EXISTING);
+            }
+        } finally {
+            Files.deleteIfExists(temporary);
+        }
+    }
+
+    private YamlConfiguration loadYaml() throws IOException {
+        YamlConfiguration yaml = new YamlConfiguration();
+        try {
+            yaml.load(stateFile.toFile());
+            return yaml;
+        } catch (InvalidConfigurationException exception) {
+            throw new IOException("state file is not valid YAML", exception);
+        }
+    }
+
+    private static GameState loadGameSafely(YamlConfiguration yaml) {
+        try {
+            GameLifecycle lifecycle = enumValue(
+                GameLifecycle.class,
+                yaml.getString("game.lifecycle"),
+                GameLifecycle.UNSTARTED
+            );
+            return new GameState(
+                lifecycle,
+                uuid(yaml.getString("game.tyrant-id")),
+                uuid(yaml.getString("game.vigilante-id")),
+                pending(yaml, "game.pending-tyrant"),
+                pending(yaml, "game.pending-vigilante"),
+                instant(yaml.getString("game.paused-at")),
+                Duration.ofSeconds(nonNegativeLong(yaml, "game.accumulated-paused-seconds")),
+                nonNegativeInt(yaml, "game.tyrant-level"),
+                nonNegativeInt(yaml, "game.unspent-choices"),
+                enumSet(TyrantUnlock.class, yaml.getStringList("game.purchases"))
+            );
+        } catch (IllegalArgumentException exception) {
+            return GameState.empty();
+        }
+    }
+
+    private static Map<UUID, PlayerState> loadPlayers(YamlConfiguration yaml) {
+        Map<UUID, PlayerState> players = new HashMap<>();
+        ConfigurationSection section = yaml.getConfigurationSection(PLAYERS);
+        if (section == null) {
+            return players;
+        }
+        for (String key : section.getKeys(false)) {
+            try {
+                UUID playerId = UUID.fromString(key);
+                String path = PLAYERS + "." + key;
+                String name = requireText(yaml.getString(path + ".name"), "player name");
+                PlayerState player = new PlayerState(
+                    playerId,
+                    name,
+                    instant(yaml.getString(path + ".last-login")),
+                    instant(yaml.getString(path + ".opted-out-until")),
+                    enumValue(
+                        TyrantClass.class,
+                        yaml.getString(path + ".tyrant-class"),
+                        TyrantClass.NONE
+                    ),
+                    uuid(yaml.getString(path + ".follower-of")),
+                    loadCooldowns(yaml, path + ".cooldowns"),
+                    enumSet(Ability.class, yaml.getStringList(path + ".ready-ability-items")),
+                    loadCapturedMobs(yaml.getMapList(path + ".captured-mobs"))
+                );
+                players.put(playerId, player);
+            } catch (IllegalArgumentException ignored) {
+                // Invalid player records grant no state.
+            }
+        }
+        return players;
+    }
+
+    private static Map<Ability, Instant> loadCooldowns(YamlConfiguration yaml, String path) {
+        Map<Ability, Instant> cooldowns = new EnumMap<>(Ability.class);
+        ConfigurationSection section = yaml.getConfigurationSection(path);
+        if (section == null) {
+            return cooldowns;
+        }
+        for (String key : section.getKeys(false)) {
+            Ability ability = enumValue(Ability.class, key, null);
+            Optional<Instant> end = instant(yaml.getString(path + "." + key));
+            if (ability != null && end.isPresent()) {
+                cooldowns.put(ability, end.orElseThrow());
+            }
+        }
+        return cooldowns;
+    }
+
+    private static List<CapturedMob> loadCapturedMobs(List<Map<?, ?>> rawMobs) {
+        List<CapturedMob> mobs = new ArrayList<>();
+        for (Map<?, ?> raw : rawMobs) {
+            try {
+                String type = requireText(
+                    raw.get("entity-type") == null ? null : raw.get("entity-type").toString(),
+                    "captured mob entity type"
+                );
+                EntityType entityType = EntityType.valueOf(type.toUpperCase(java.util.Locale.ROOT));
+                if (entityType == EntityType.ENDER_DRAGON) {
+                    continue;
+                }
+                Map<String, String> data = new HashMap<>();
+                Object rawData = raw.get("data");
+                if (rawData instanceof Map<?, ?> values) {
+                    for (Map.Entry<?, ?> entry : values.entrySet()) {
+                        if (entry.getKey() != null && entry.getValue() != null) {
+                            data.put(entry.getKey().toString(), entry.getValue().toString());
+                        }
+                    }
+                }
+                mobs.add(new CapturedMob(entityType.name(), data));
+            } catch (IllegalArgumentException ignored) {
+                // Unknown or malformed entities are not restored.
+            }
+        }
+        return List.copyOf(mobs);
+    }
+
+    private static void saveGame(YamlConfiguration yaml, GameState game) {
+        yaml.set("game.lifecycle", game.lifecycle().name());
+        yaml.set("game.tyrant-id", text(game.tyrantId()));
+        yaml.set("game.vigilante-id", text(game.vigilanteId()));
+        savePending(yaml, "game.pending-tyrant", game.pendingTyrant());
+        savePending(yaml, "game.pending-vigilante", game.pendingVigilante());
+        yaml.set("game.paused-at", instantText(game.pausedAt()));
+        yaml.set("game.accumulated-paused-seconds", game.accumulatedPausedTime().toSeconds());
+        yaml.set("game.tyrant-level", game.tyrantLevel());
+        yaml.set("game.unspent-choices", game.unspentChoices());
+        yaml.set("game.purchases", game.purchases().stream().map(Enum::name).sorted().toList());
+    }
+
+    private static void savePlayer(YamlConfiguration yaml, PlayerState player) {
+        String path = PLAYERS + "." + player.playerId();
+        yaml.set(path + ".name", player.latestName());
+        yaml.set(path + ".last-login", instantText(player.lastLogin()));
+        yaml.set(path + ".opted-out-until", instantText(player.optedOutUntil()));
+        yaml.set(path + ".tyrant-class", player.tyrantClass().name());
+        yaml.set(path + ".follower-of", text(player.followerOf()));
+        yaml.set(path + ".cooldowns", null);
+        for (Map.Entry<Ability, Instant> cooldown : player.cooldownEnds().entrySet()) {
+            yaml.set(path + ".cooldowns." + cooldown.getKey().name(), cooldown.getValue().toString());
+        }
+        yaml.set(
+            path + ".ready-ability-items",
+            player.readyAbilityItems().stream().map(Enum::name).sorted().toList()
+        );
+        List<Map<String, Object>> mobs = new ArrayList<>();
+        for (CapturedMob mob : player.capturedMobs()) {
+            Map<String, Object> serialized = new LinkedHashMap<>();
+            serialized.put("entity-type", mob.entityType());
+            serialized.put("data", mob.data());
+            mobs.add(serialized);
+        }
+        yaml.set(path + ".captured-mobs", mobs);
+    }
+
+    private static void removeAbsentPlayers(YamlConfiguration yaml, Set<UUID> retained) {
+        ConfigurationSection section = yaml.getConfigurationSection(PLAYERS);
+        if (section == null) {
+            return;
+        }
+        for (String key : section.getKeys(false)) {
+            try {
+                if (!retained.contains(UUID.fromString(key))) {
+                    yaml.set(PLAYERS + "." + key, null);
+                }
+            } catch (IllegalArgumentException exception) {
+                yaml.set(PLAYERS + "." + key, null);
+            }
+        }
+    }
+
+    private static Optional<PendingSelection> pending(YamlConfiguration yaml, String path) {
+        Optional<UUID> candidate = uuid(yaml.getString(path + ".candidate-id"));
+        Optional<Instant> expiresAt = instant(yaml.getString(path + ".expires-at"));
+        if (candidate.isEmpty() && expiresAt.isEmpty()) {
+            return Optional.empty();
+        }
+        if (candidate.isEmpty() || expiresAt.isEmpty()) {
+            throw new IllegalArgumentException("incomplete pending selection");
+        }
+        return Optional.of(new PendingSelection(candidate.orElseThrow(), expiresAt.orElseThrow()));
+    }
+
+    private static void savePending(
+        YamlConfiguration yaml,
+        String path,
+        Optional<PendingSelection> pending
+    ) {
+        yaml.set(path, null);
+        pending.ifPresent(selection -> {
+            yaml.set(path + ".candidate-id", selection.candidateId().toString());
+            yaml.set(path + ".expires-at", selection.expiresAt().toString());
+        });
+    }
+
+    private static Optional<UUID> uuid(String value) {
+        if (value == null || value.isBlank()) {
+            return Optional.empty();
+        }
+        return Optional.of(UUID.fromString(value));
+    }
+
+    private static Optional<Instant> instant(String value) {
+        if (value == null || value.isBlank()) {
+            return Optional.empty();
+        }
+        try {
+            return Optional.of(Instant.parse(value));
+        } catch (DateTimeParseException exception) {
+            throw new IllegalArgumentException("invalid RFC 3339 instant", exception);
+        }
+    }
+
+    private static String instantText(Optional<Instant> value) {
+        return value.map(Instant::toString).orElse(null);
+    }
+
+    private static String text(Optional<UUID> value) {
+        return value.map(UUID::toString).orElse(null);
+    }
+
+    private static int nonNegativeInt(YamlConfiguration yaml, String path) {
+        if (!yaml.isInt(path)) {
+            return 0;
+        }
+        int value = yaml.getInt(path);
+        if (value < 0) {
+            throw new IllegalArgumentException(path + " must not be negative");
+        }
+        return value;
+    }
+
+    private static long nonNegativeLong(YamlConfiguration yaml, String path) {
+        if (!yaml.isLong(path) && !yaml.isInt(path)) {
+            return 0L;
+        }
+        long value = yaml.getLong(path);
+        if (value < 0L) {
+            throw new IllegalArgumentException(path + " must not be negative");
+        }
+        return value;
+    }
+
+    private static <E extends Enum<E>> E enumValue(
+        Class<E> type,
+        String value,
+        E defaultValue
+    ) {
+        if (value == null || value.isBlank()) {
+            return defaultValue;
+        }
+        return Enum.valueOf(type, value.trim().toUpperCase(java.util.Locale.ROOT));
+    }
+
+    private static <E extends Enum<E>> Set<E> enumSet(Class<E> type, List<String> values) {
+        Set<E> result = EnumSet.noneOf(type);
+        for (String value : values) {
+            result.add(enumValue(type, value, null));
+        }
+        return Set.copyOf(result);
+    }
+
+    private static String requireText(String value, String description) {
+        if (value == null || value.isBlank()) {
+            throw new IllegalArgumentException(description + " must not be blank");
+        }
+        return value.trim();
+    }
+}