feat(quests): add quest creation and reward escrow

src/main/java/games/dmg/spigotquestboard/BlockMaterialCatalog.java

@@ -0,0 +1,9 @@
+package games.dmg.spigotquestboard;
+
+import java.util.List;
+import java.util.Optional;
+
+interface BlockMaterialCatalog {
+    Optional<String> normalizeBlock(String input);
+    List<String> suggest(String prefix);
+}

src/main/java/games/dmg/spigotquestboard/BukkitBlockMaterialCatalog.java

@@ -0,0 +1,30 @@
+package games.dmg.spigotquestboard;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Locale;
+import java.util.Optional;
+import org.bukkit.Material;
+
+final class BukkitBlockMaterialCatalog implements BlockMaterialCatalog {
+    @Override
+    public Optional<String> normalizeBlock(String input) {
+        Material material = Material.matchMaterial(input == null ? "" : input);
+        if (material == null || material.isAir() || !material.isBlock()) {
+            return Optional.empty();
+        }
+        return Optional.of(material.name());
+    }
+
+    @Override
+    public List<String> suggest(String prefix) {
+        String normalizedPrefix = prefix.toUpperCase(Locale.ROOT);
+        return Arrays.stream(Material.values())
+            .filter(material -> material.isBlock() && !material.isAir())
+            .map(Material::name)
+            .filter(name -> name.startsWith(normalizedPrefix))
+            .sorted()
+            .limit(100)
+            .toList();
+    }
+}

src/main/java/games/dmg/spigotquestboard/BukkitHeldRewardInventory.java

@@ -0,0 +1,36 @@
+package games.dmg.spigotquestboard;
+
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+
+final class BukkitHeldRewardInventory implements HeldRewardInventory {
+    @Override
+    public RemovedReward remove(Player player) {
+        PlayerInventory inventory = player.getInventory();
+        ItemStack held = inventory.getItemInMainHand();
+        if (held.getType().isAir() || held.getAmount() <= 0) {
+            throw new IllegalArgumentException("Hold the reward stack in your main hand");
+        }
+        int slot = inventory.getHeldItemSlot();
+        ItemStack snapshot = held.clone();
+        EscrowItem escrow = EscrowItem.fromItemStack(snapshot);
+        inventory.clear(slot);
+        return new RemovedReward() {
+            private boolean rolledBack;
+
+            @Override
+            public EscrowItem item() {
+                return escrow;
+            }
+
+            @Override
+            public void rollback() {
+                if (!rolledBack) {
+                    inventory.setItem(slot, snapshot);
+                    rolledBack = true;
+                }
+            }
+        };
+    }
+}

src/main/java/games/dmg/spigotquestboard/EscrowItem.java

@@ -0,0 +1,50 @@
+package games.dmg.spigotquestboard;
+
+import java.util.Base64;
+import java.util.Objects;
+import org.bukkit.Material;
+import org.bukkit.inventory.ItemStack;
+
+record EscrowItem(String material, int amount, String serializedItem) {
+    EscrowItem {
+        Objects.requireNonNull(material, "material");
+        material = material.trim().toUpperCase(java.util.Locale.ROOT);
+        if (material.isEmpty() || "AIR".equals(material)) {
+            throw new IllegalArgumentException("Invalid escrow material: " + material);
+        }
+        if (amount <= 0) {
+            throw new IllegalArgumentException("Escrow amount must be positive");
+        }
+        if (serializedItem != null && serializedItem.isBlank()) {
+            throw new IllegalArgumentException("Serialized item must not be blank");
+        }
+    }
+
+    static EscrowItem fromItemStack(ItemStack stack) {
+        Objects.requireNonNull(stack, "stack");
+        if (stack.getType().isAir() || stack.getAmount() <= 0) {
+            throw new IllegalArgumentException("Reward stack must not be empty");
+        }
+        ItemStack snapshot = stack.clone();
+        return new EscrowItem(
+            snapshot.getType().name(), snapshot.getAmount(),
+            Base64.getEncoder().encodeToString(snapshot.serializeAsBytes())
+        );
+    }
+
+    ItemStack toItemStack() {
+        if (serializedItem == null) {
+            return new ItemStack(Objects.requireNonNull(Material.matchMaterial(material)), amount);
+        }
+        final ItemStack stack;
+        try {
+            stack = ItemStack.deserializeBytes(Base64.getDecoder().decode(serializedItem));
+        } catch (IllegalArgumentException exception) {
+            throw new IllegalStateException("Invalid serialized escrow item", exception);
+        }
+        if (!stack.getType().name().equals(material) || stack.getAmount() != amount) {
+            throw new IllegalStateException("Serialized escrow item does not match its envelope");
+        }
+        return stack;
+    }
+}

src/main/java/games/dmg/spigotquestboard/HeldRewardInventory.java

@@ -0,0 +1,12 @@
+package games.dmg.spigotquestboard;
+
+import org.bukkit.entity.Player;
+
+interface HeldRewardInventory {
+    RemovedReward remove(Player player);
+
+    interface RemovedReward {
+        EscrowItem item();
+        void rollback();
+    }
+}

src/main/java/games/dmg/spigotquestboard/Quest.java

@@ -0,0 +1,40 @@
+package games.dmg.spigotquestboard;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.Objects;
+import java.util.UUID;
+
+record Quest(
+    UUID id,
+    UUID issuerId,
+    String issuerName,
+    String requestedMaterial,
+    int requestedAmount,
+    List<EscrowItem> reward,
+    Instant createdAt,
+    Instant expiresAt
+) {
+    Quest {
+        Objects.requireNonNull(id, "id");
+        Objects.requireNonNull(issuerId, "issuerId");
+        if (Objects.requireNonNull(issuerName, "issuerName").isBlank()) {
+            throw new IllegalArgumentException("Issuer name must not be blank");
+        }
+        if (Objects.requireNonNull(requestedMaterial, "requestedMaterial").isBlank()) {
+            throw new IllegalArgumentException("Requested material must not be blank");
+        }
+        if (requestedAmount <= 0) {
+            throw new IllegalArgumentException("Requested amount must be positive");
+        }
+        reward = List.copyOf(Objects.requireNonNull(reward, "reward"));
+        if (reward.isEmpty()) {
+            throw new IllegalArgumentException("Reward must not be empty");
+        }
+        Objects.requireNonNull(createdAt, "createdAt");
+        Objects.requireNonNull(expiresAt, "expiresAt");
+        if (!expiresAt.isAfter(createdAt)) {
+            throw new IllegalArgumentException("Expiration must follow creation");
+        }
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestBoardDialogUi.java

@@ -1,28 +1,88 @@
 package games.dmg.spigotquestboard;
 
 import io.papermc.paper.dialog.Dialog;
+import io.papermc.paper.registry.data.dialog.ActionButton;
 import io.papermc.paper.registry.data.dialog.DialogBase;
+import io.papermc.paper.registry.data.dialog.action.DialogAction;
 import io.papermc.paper.registry.data.dialog.body.DialogBody;
+import io.papermc.paper.registry.data.dialog.input.DialogInput;
 import io.papermc.paper.registry.data.dialog.type.DialogType;
+import java.io.IOException;
+import java.time.Clock;
+import java.time.Duration;
 import java.util.List;
+import java.util.Objects;
 import net.kyori.adventure.text.Component;
+import net.kyori.adventure.text.event.ClickCallback;
 import org.bukkit.entity.Player;
 
 final class QuestBoardDialogUi implements QuestBoardUi {
+    private final QuestCreationGateway creator;
+    private final Clock clock;
+
+    QuestBoardDialogUi(QuestCreationGateway creator, Clock clock) {
+        this.creator = Objects.requireNonNull(creator, "creator");
+        this.clock = Objects.requireNonNull(clock, "clock");
+    }
+
     @Override
     public void open(Player player) {
-        DialogBase base = DialogBase.builder(Component.text("Quest Board"))
-            .externalTitle(Component.text("Quest Board"))
-            .body(List.of(DialogBody.plainMessage(
-                Component.text("No active quests or claimable items."), 420
-            )))
+        ActionButton create = ActionButton.builder(Component.text("Create quest"))
+            .tooltip(Component.text("Escrow your held stack and publish this quest"))
+            .width(150)
+            .action(DialogAction.customClick((response, audience) -> {
+                if (audience instanceof Player respondingPlayer) {
+                    submit(
+                        respondingPlayer,
+                        response.getText("requested_material"),
+                        response.getText("requested_quantity")
+                    );
+                }
+            }, ClickCallback.Options.builder()
+                .uses(1)
+                .lifetime(Duration.ofMinutes(10))
+                .build()))
+            .build();
+        DialogBase base = DialogBase.builder(Component.text("Create a block-delivery quest"))
+            .externalTitle(Component.text("Quest Board — Create"))
+            .body(List.of(DialogBody.plainMessage(Component.text(
+                "Hold the reward in your main hand. The entire exact stack, including all item metadata, "
+                    + "will be removed and held in escrow only if this quest saves successfully."
+            ), 420)))
+            .inputs(List.of(
+                DialogInput.text("requested_material", Component.text("Requested block"))
+                    .initial("")
+                    .maxLength(64)
+                    .build(),
+                DialogInput.text("requested_quantity", Component.text("Quantity"))
+                    .initial("64")
+                    .maxLength(10)
+                    .build()
+            ))
             .canCloseWithEscape(true)
             .pause(false)
             .afterAction(DialogBase.DialogAfterAction.CLOSE)
             .build();
-        Dialog dialog = Dialog.create(factory -> factory.empty()
+        player.showDialog(Dialog.create(factory -> factory.empty()
             .base(base)
-            .type(DialogType.notice()));
-        player.showDialog(dialog);
+            .type(DialogType.notice(create))));
+    }
+
+    void submit(Player player, String material, String quantityText) {
+        final int quantity;
+        try {
+            quantity = Integer.parseInt(quantityText == null ? "" : quantityText.trim());
+        } catch (NumberFormatException exception) {
+            player.sendMessage("Quest quantity must be a positive whole number.");
+            return;
+        }
+        try {
+            Quest quest = creator.create(player, material, quantity, clock.instant());
+            player.sendMessage("Quest " + quest.id() + " created. Your exact held stack is now escrowed.");
+        } catch (IllegalArgumentException exception) {
+            player.sendMessage(exception.getMessage());
+        } catch (IOException exception) {
+            player.sendMessage("The quest could not be saved. Your held reward was restored.");
+        }
     }
 }

src/main/java/games/dmg/spigotquestboard/QuestCommand.java

@@ -0,0 +1,84 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.util.List;
+import java.util.Locale;
+import java.util.Objects;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandExecutor;
+import org.bukkit.command.CommandSender;
+import org.bukkit.command.TabCompleter;
+import org.bukkit.entity.Player;
+
+final class QuestCommand implements CommandExecutor, TabCompleter {
+    private static final List<String> QUANTITIES = List.of("1", "16", "32", "64");
+    private final QuestCreationGateway creator;
+    private final Clock clock;
+
+    QuestCommand(QuestCreationGateway creator, Clock clock) {
+        this.creator = Objects.requireNonNull(creator, "creator");
+        this.clock = Objects.requireNonNull(clock, "clock");
+    }
+
+    @Override
+    public boolean onCommand(
+        CommandSender sender, Command command, String label, String[] arguments
+    ) {
+        if (!(sender instanceof Player player)) {
+            sender.sendMessage("Only players can create quests with inventory rewards.");
+            return true;
+        }
+        if (arguments.length != 3 || !"create".equalsIgnoreCase(arguments[0])) {
+            usage(sender);
+            return true;
+        }
+        final int quantity;
+        try {
+            quantity = Integer.parseInt(arguments[2]);
+        } catch (NumberFormatException exception) {
+            sender.sendMessage("Quest quantity must be a positive whole number.");
+            return true;
+        }
+        try {
+            Quest quest = creator.create(player, arguments[1], quantity, clock.instant());
+            sender.sendMessage("Quest " + quest.id() + " created. Your exact held stack is now escrowed.");
+        } catch (IllegalArgumentException exception) {
+            sender.sendMessage(exception.getMessage());
+        } catch (IOException exception) {
+            sender.sendMessage("The quest could not be saved. Your held reward was restored.");
+        }
+        return true;
+    }
+
+    @Override
+    public List<String> onTabComplete(
+        CommandSender sender, Command command, String alias, String[] arguments
+    ) {
+        if (!(sender instanceof Player)) {
+            return List.of();
+        }
+        if (arguments.length == 1) {
+            return startsWith(List.of("create"), arguments[0]);
+        }
+        if (arguments.length == 2 && "create".equalsIgnoreCase(arguments[0])) {
+            return creator.suggestBlockMaterials(arguments[1]);
+        }
+        if (arguments.length == 3 && "create".equalsIgnoreCase(arguments[0])) {
+            return startsWith(QUANTITIES, arguments[2]);
+        }
+        return List.of();
+    }
+
+    private static List<String> startsWith(List<String> candidates, String prefix) {
+        String normalized = prefix.toLowerCase(Locale.ROOT);
+        return candidates.stream()
+            .filter(candidate -> candidate.toLowerCase(Locale.ROOT).startsWith(normalized))
+            .toList();
+    }
+
+    private static void usage(CommandSender sender) {
+        sender.sendMessage("Usage: /quests create <block> <quantity>");
+        sender.sendMessage("Hold the entire reward stack in your main hand; its exact metadata will be escrowed.");
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestCreationController.java

@@ -0,0 +1,52 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+import java.util.Objects;
+import org.bukkit.entity.Player;
+
+final class QuestCreationController implements QuestCreationGateway {
+    private final QuestService quests;
+    private final BlockMaterialCatalog materials;
+    private final HeldRewardInventory rewards;
+
+    QuestCreationController(
+        QuestService quests,
+        BlockMaterialCatalog materials,
+        HeldRewardInventory rewards
+    ) {
+        this.quests = Objects.requireNonNull(quests, "quests");
+        this.materials = Objects.requireNonNull(materials, "materials");
+        this.rewards = Objects.requireNonNull(rewards, "rewards");
+    }
+
+    @Override
+    public Quest create(
+        Player player, String requestedMaterial, int requestedAmount, Instant createdAt
+    ) throws IOException {
+        Objects.requireNonNull(player, "player");
+        if (requestedAmount <= 0) {
+            throw new IllegalArgumentException("Requested quantity must be positive");
+        }
+        String material = materials.normalizeBlock(requestedMaterial)
+            .orElseThrow(() -> new IllegalArgumentException(
+                "Requested material must be a valid block"
+            ));
+        HeldRewardInventory.RemovedReward removed = rewards.remove(player);
+        try {
+            return quests.create(
+                player.getUniqueId(), player.getName(), material, requestedAmount,
+                List.of(removed.item()), createdAt
+            );
+        } catch (IOException | RuntimeException exception) {
+            removed.rollback();
+            throw exception;
+        }
+    }
+
+    @Override
+    public List<String> suggestBlockMaterials(String prefix) {
+        return materials.suggest(prefix == null ? "" : prefix);
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestCreationGateway.java

@@ -0,0 +1,13 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+import org.bukkit.entity.Player;
+
+interface QuestCreationGateway {
+    Quest create(Player player, String requestedMaterial, int requestedAmount, Instant createdAt)
+        throws IOException;
+
+    List<String> suggestBlockMaterials(String prefix);
+}

src/main/java/games/dmg/spigotquestboard/QuestRepository.java

@@ -0,0 +1,8 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+
+interface QuestRepository {
+    QuestState load() throws IOException;
+    void save(QuestState state) throws IOException;
+}

src/main/java/games/dmg/spigotquestboard/QuestService.java

@@ -0,0 +1,51 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Locale;
+import java.util.Objects;
+import java.util.UUID;
+
+final class QuestService {
+    private final QuestRepository repository;
+    private Map<UUID, Quest> quests;
+
+    QuestService(QuestRepository repository) throws IOException {
+        this.repository = Objects.requireNonNull(repository, "repository");
+        quests = new LinkedHashMap<>(repository.load().quests());
+    }
+
+    synchronized Quest create(
+        UUID issuerId,
+        String issuerName,
+        String requestedMaterial,
+        int requestedAmount,
+        List<EscrowItem> reward,
+        Instant createdAt
+    ) throws IOException {
+        Objects.requireNonNull(issuerId, "issuerId");
+        Objects.requireNonNull(createdAt, "createdAt");
+        String material = Objects.requireNonNull(requestedMaterial, "requestedMaterial")
+            .trim().toUpperCase(Locale.ROOT);
+        if (material.isEmpty() || "AIR".equals(material)) {
+            throw new IllegalArgumentException("Requested material must be a block");
+        }
+        Quest quest = new Quest(
+            UUID.randomUUID(), issuerId, issuerName, material, requestedAmount,
+            reward, createdAt, createdAt.plus(7, ChronoUnit.DAYS)
+        );
+        Map<UUID, Quest> candidate = new LinkedHashMap<>(quests);
+        candidate.put(quest.id(), quest);
+        repository.save(new QuestState(candidate));
+        quests = Map.copyOf(candidate);
+        return quest;
+    }
+
+    synchronized QuestState state() {
+        return new QuestState(quests);
+    }
+}

src/main/java/games/dmg/spigotquestboard/QuestState.java

@@ -0,0 +1,20 @@
+package games.dmg.spigotquestboard;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.UUID;
+
+record QuestState(Map<UUID, Quest> quests) {
+    QuestState {
+        quests = Map.copyOf(Objects.requireNonNull(quests, "quests"));
+        for (Map.Entry<UUID, Quest> entry : quests.entrySet()) {
+            if (!entry.getKey().equals(entry.getValue().id())) {
+                throw new IllegalArgumentException("Quest map key does not match quest id");
+            }
+        }
+    }
+
+    static QuestState empty() {
+        return new QuestState(Map.of());
+    }
+}

src/main/java/games/dmg/spigotquestboard/SpigotQuestBoardPlugin.java

@@ -1,6 +1,7 @@
 package games.dmg.spigotquestboard;
 
 import java.io.IOException;
+import java.time.Clock;
 import java.util.Objects;
 import java.util.logging.Level;
 import org.bukkit.command.PluginCommand;
@@ -10,22 +11,39 @@ public final class SpigotQuestBoardPlugin extends JavaPlugin {
     @Override
     public void onEnable() {
         final BoardRegistry boards;
+        final QuestService quests;
         try {
             boards = new BoardRegistry(new YamlBoardRepository(
                 getDataFolder().toPath().resolve("boards.yml")
             ));
+            quests = new QuestService(new YamlQuestRepository(
+                getDataFolder().toPath().resolve("quests.yml")
+            ));
         } catch (IOException exception) {
-            getLogger().log(Level.SEVERE, "Could not load quest boards", exception);
+            getLogger().log(Level.SEVERE, "Could not load quest board state", exception);
             getServer().getPluginManager().disablePlugin(this);
             return;
         }
 
         QuestAdminCommand admin = new QuestAdminCommand(boards);
         command("questadmin").setExecutor(admin);
+
+        QuestCreationGateway creator = new QuestCreationController(
+            quests, new BukkitBlockMaterialCatalog(), new BukkitHeldRewardInventory()
+        );
+        QuestCommand questCommand = new QuestCommand(creator, Clock.systemUTC());
+        command("quests").setExecutor(questCommand);
+        command("quests").setTabCompleter(questCommand);
         getServer().getPluginManager().registerEvents(
-            new QuestBoardInteractionListener(boards, new QuestBoardDialogUi()), this
+            new QuestBoardInteractionListener(
+                boards, new QuestBoardDialogUi(creator, Clock.systemUTC())
+            ),
+            this
+        );
+        getLogger().info(
+            "Spigot Quest Board enabled with " + boards.size() + " boards and "
+                + quests.state().quests().size() + " quests."
         );
-        getLogger().info("Spigot Quest Board enabled with " + boards.size() + " boards.");
     }
 
     private PluginCommand command(String name) {

src/main/java/games/dmg/spigotquestboard/YamlQuestRepository.java

@@ -0,0 +1,142 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.time.Instant;
+import java.time.format.DateTimeParseException;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import org.bukkit.configuration.InvalidConfigurationException;
+import org.bukkit.configuration.file.YamlConfiguration;
+
+final class YamlQuestRepository implements QuestRepository {
+    private final Path path;
+
+    YamlQuestRepository(Path path) {
+        this.path = path;
+    }
+
+    @Override
+    public QuestState load() throws IOException {
+        if (!Files.exists(path)) {
+            return QuestState.empty();
+        }
+        YamlConfiguration yaml = new YamlConfiguration();
+        try {
+            yaml.load(path.toFile());
+        } catch (InvalidConfigurationException exception) {
+            throw new IOException("Invalid quest state", exception);
+        }
+        Map<UUID, Quest> quests = new LinkedHashMap<>();
+        try {
+            for (Map<?, ?> entry : yaml.getMapList("quests")) {
+                UUID id = UUID.fromString(requiredString(entry, "id"));
+                Quest quest = new Quest(
+                    id,
+                    UUID.fromString(requiredString(entry, "issuer-id")),
+                    requiredString(entry, "issuer-name"),
+                    requiredString(entry, "requested-material"),
+                    requiredInteger(entry, "requested-amount"),
+                    readRewards(entry.get("reward")),
+                    Instant.parse(requiredString(entry, "created-at")),
+                    Instant.parse(requiredString(entry, "expires-at"))
+                );
+                if (quests.put(id, quest) != null) {
+                    throw new IllegalArgumentException("Duplicate quest id: " + id);
+                }
+            }
+        } catch (IllegalArgumentException | DateTimeParseException exception) {
+            throw new IOException("Invalid quest record", exception);
+        }
+        return new QuestState(quests);
+    }
+
+    @Override
+    public void save(QuestState state) throws IOException {
+        YamlConfiguration yaml = new YamlConfiguration();
+        List<Map<String, Object>> serializedQuests = new ArrayList<>();
+        for (Quest quest : state.quests().values()) {
+            Map<String, Object> serialized = new LinkedHashMap<>();
+            serialized.put("id", quest.id().toString());
+            serialized.put("issuer-id", quest.issuerId().toString());
+            serialized.put("issuer-name", quest.issuerName());
+            serialized.put("requested-material", quest.requestedMaterial());
+            serialized.put("requested-amount", quest.requestedAmount());
+            serialized.put("created-at", quest.createdAt().toString());
+            serialized.put("expires-at", quest.expiresAt().toString());
+            List<Map<String, Object>> rewards = new ArrayList<>();
+            for (EscrowItem reward : quest.reward()) {
+                Map<String, Object> serializedReward = new LinkedHashMap<>();
+                serializedReward.put("material", reward.material());
+                serializedReward.put("amount", reward.amount());
+                if (reward.serializedItem() != null) {
+                    serializedReward.put("item-data", reward.serializedItem());
+                }
+                rewards.add(serializedReward);
+            }
+            serialized.put("reward", rewards);
+            serializedQuests.add(serialized);
+        }
+        yaml.set("quests", serializedQuests);
+        writeAtomically(yaml);
+    }
+
+    private void writeAtomically(YamlConfiguration yaml) throws IOException {
+        Path parent = path.toAbsolutePath().getParent();
+        Files.createDirectories(parent);
+        Path temporary = Files.createTempFile(parent, path.getFileName().toString(), ".tmp");
+        try {
+            yaml.save(temporary.toFile());
+            try {
+                Files.move(temporary, path, StandardCopyOption.REPLACE_EXISTING,
+                    StandardCopyOption.ATOMIC_MOVE);
+            } catch (AtomicMoveNotSupportedException exception) {
+                Files.move(temporary, path, StandardCopyOption.REPLACE_EXISTING);
+            }
+        } finally {
+            Files.deleteIfExists(temporary);
+        }
+    }
+
+    private static List<EscrowItem> readRewards(Object value) {
+        if (!(value instanceof List<?> entries) || entries.isEmpty()) {
+            throw new IllegalArgumentException("Missing reward");
+        }
+        List<EscrowItem> rewards = new ArrayList<>();
+        for (Object rawEntry : entries) {
+            if (!(rawEntry instanceof Map<?, ?> entry)) {
+                throw new IllegalArgumentException("Invalid reward");
+            }
+            Object data = entry.get("item-data");
+            if (data != null && !(data instanceof String)) {
+                throw new IllegalArgumentException("Invalid item-data");
+            }
+            rewards.add(new EscrowItem(
+                requiredString(entry, "material"), requiredInteger(entry, "amount"), (String) data
+            ));
+        }
+        return rewards;
+    }
+
+    private static String requiredString(Map<?, ?> entry, String key) {
+        Object value = entry.get(key);
+        if (!(value instanceof String text) || text.isBlank()) {
+            throw new IllegalArgumentException("Missing " + key);
+        }
+        return text;
+    }
+
+    private static int requiredInteger(Map<?, ?> entry, String key) {
+        Object value = entry.get(key);
+        if (!(value instanceof Number number)) {
+            throw new IllegalArgumentException("Missing " + key);
+        }
+        return number.intValue();
+    }
+}