feat(quests): add issuer quest cancellation

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

@@ -21,10 +21,11 @@ final class QuestBoardDialogUi implements QuestBoardUi {
     private final QuestCreationGateway creator;
     private final QuestBrowser browser;
     private final QuestCompletionGateway completer;
+    private final QuestCancellationGateway canceller;
     private final Clock clock;
 
     QuestBoardDialogUi(QuestCreationGateway creator, QuestBrowser browser, Clock clock) {
-        this(creator, browser, null, clock);
+        this(creator, browser, null, null, clock);
     }
 
     QuestBoardDialogUi(
@@ -32,10 +33,21 @@ final class QuestBoardDialogUi implements QuestBoardUi {
         QuestBrowser browser,
         QuestCompletionGateway completer,
         Clock clock
+    ) {
+        this(creator, browser, completer, null, clock);
+    }
+
+    QuestBoardDialogUi(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        QuestCancellationGateway canceller,
+        Clock clock
     ) {
         this.creator = Objects.requireNonNull(creator, "creator");
         this.browser = Objects.requireNonNull(browser, "browser");
         this.completer = completer;
+        this.canceller = canceller;
         this.clock = Objects.requireNonNull(clock, "clock");
     }
 
@@ -62,10 +74,13 @@ final class QuestBoardDialogUi implements QuestBoardUi {
         String listing = QuestListingFormatter.formatAll(activeQuests, now);
         List<ActionButton> actions = new ArrayList<>();
         actions.add(create);
-        if (completer != null) {
-            for (Quest quest : activeQuests) {
+        for (Quest quest : activeQuests) {
+            if (completer != null) {
                 actions.add(completionButton(quest));
             }
+            if (canceller != null && quest.issuerId().equals(player.getUniqueId())) {
+                actions.add(cancellationButton(quest));
+            }
         }
         DialogBase base = DialogBase.builder(Component.text("Quest Board"))
             .externalTitle(Component.text("Quest Board — Active quests and create"))
@@ -116,6 +131,44 @@ final class QuestBoardDialogUi implements QuestBoardUi {
             .build();
     }
 
+    private ActionButton cancellationButton(Quest quest) {
+        String id = quest.id().toString();
+        return ActionButton.builder(Component.text(
+                "Cancel " + quest.requestedAmount() + " " + quest.requestedMaterial()
+            ))
+            .tooltip(Component.text("Return the escrowed reward to claims for quest " + id))
+            .width(250)
+            .action(DialogAction.customClick((response, audience) -> {
+                if (audience instanceof Player respondingPlayer) {
+                    submitCancellation(respondingPlayer, id);
+                }
+            }, ClickCallback.Options.builder()
+                .uses(1)
+                .lifetime(Duration.ofMinutes(10))
+                .build()))
+            .build();
+    }
+
+    List<String> cancellableQuestIds(Player player) {
+        return browser.cancellableQuestIds(player.getUniqueId(), clock.instant());
+    }
+
+    void submitCancellation(Player player, String questId) {
+        if (canceller == null) {
+            player.sendMessage("Quest cancellation is unavailable.");
+            return;
+        }
+        try {
+            canceller.cancel(player, questId, clock.instant());
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            player.sendMessage(exception.getMessage());
+        } catch (IOException exception) {
+            player.sendMessage(
+                "The quest could not be saved. It remains active and its reward remains escrowed."
+            );
+        }
+    }
+
     void submitCompletion(Player player, String questId) {
         if (completer == null) {
             player.sendMessage("Quest completion is unavailable.");

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

@@ -0,0 +1,31 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.Objects;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+
+final class QuestCancellationController implements QuestCancellationGateway {
+    private final QuestService quests;
+
+    QuestCancellationController(QuestService quests) {
+        this.quests = Objects.requireNonNull(quests, "quests");
+    }
+
+    @Override
+    public QuestClaim cancel(Player player, String questId, Instant cancelledAt) throws IOException {
+        Objects.requireNonNull(player, "player");
+        final UUID id;
+        try {
+            id = UUID.fromString(Objects.requireNonNull(questId, "questId"));
+        } catch (IllegalArgumentException exception) {
+            throw new IllegalArgumentException("Quest identifier must be a valid UUID.", exception);
+        }
+        QuestClaim claim = quests.cancel(id, player.getUniqueId(), cancelledAt);
+        player.sendMessage(
+            "Quest " + id + " cancelled. Your exact escrowed reward is ready to claim at a quest board."
+        );
+        return claim;
+    }
+}

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

@@ -0,0 +1,9 @@
+package games.dmg.spigotquestboard;
+
+import java.io.IOException;
+import java.time.Instant;
+import org.bukkit.entity.Player;
+
+interface QuestCancellationGateway {
+    QuestClaim cancel(Player player, String questId, Instant cancelledAt) throws IOException;
+}

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

@@ -17,10 +17,11 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
     private final QuestCreationGateway creator;
     private final QuestBrowser browser;
     private final QuestCompletionGateway completer;
+    private final QuestCancellationGateway canceller;
     private final Clock clock;
 
     QuestCommand(QuestCreationGateway creator, QuestBrowser browser, Clock clock) {
-        this(creator, browser, null, clock);
+        this(creator, browser, null, null, clock);
     }
 
     QuestCommand(
@@ -28,10 +29,21 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
         QuestBrowser browser,
         QuestCompletionGateway completer,
         Clock clock
+    ) {
+        this(creator, browser, completer, null, clock);
+    }
+
+    QuestCommand(
+        QuestCreationGateway creator,
+        QuestBrowser browser,
+        QuestCompletionGateway completer,
+        QuestCancellationGateway canceller,
+        Clock clock
     ) {
         this.creator = Objects.requireNonNull(creator, "creator");
         this.browser = Objects.requireNonNull(browser, "browser");
         this.completer = completer;
+        this.canceller = canceller;
         this.clock = Objects.requireNonNull(clock, "clock");
     }
 
@@ -65,6 +77,26 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
             }
             return true;
         }
+        if (arguments.length == 2 && "cancel".equalsIgnoreCase(arguments[0])) {
+            if (!(sender instanceof Player player)) {
+                sender.sendMessage("Only players can cancel quests.");
+                return true;
+            }
+            if (canceller == null) {
+                sender.sendMessage("Quest cancellation is unavailable.");
+                return true;
+            }
+            try {
+                canceller.cancel(player, arguments[1], clock.instant());
+            } catch (IllegalArgumentException | IllegalStateException exception) {
+                sender.sendMessage(exception.getMessage());
+            } catch (IOException exception) {
+                sender.sendMessage(
+                    "The quest could not be saved. It remains active and its reward remains escrowed."
+                );
+            }
+            return true;
+        }
         if (arguments.length != 3 || !"create".equalsIgnoreCase(arguments[0])) {
             usage(sender);
             return true;
@@ -99,7 +131,7 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
             return List.of();
         }
         if (arguments.length == 1) {
-            return startsWith(List.of("create", "list", "complete"), arguments[0]);
+            return startsWith(List.of("create", "list", "complete", "cancel"), arguments[0]);
         }
         if (arguments.length == 2 && "create".equalsIgnoreCase(arguments[0])) {
             return creator.suggestBlockMaterials(arguments[1]);
@@ -129,7 +161,7 @@ final class QuestCommand implements CommandExecutor, TabCompleter {
     private static void usage(CommandSender sender) {
         sender.sendMessage(
             "Usage: /quests [list] | /quests create <block> <quantity> | "
-                + "/quests complete <quest>"
+                + "/quests complete <quest> | /quests cancel <quest>"
         );
         sender.sendMessage("Hold the entire reward stack in your main hand; its exact metadata will be escrowed.");
     }

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

@@ -107,6 +107,42 @@ final class QuestService implements QuestBrowser {
         return new QuestCompletion(completed, claim, completed.reward());
     }
 
+    synchronized QuestClaim cancel(UUID questId, UUID issuerId, Instant cancelledAt)
+        throws IOException {
+        Objects.requireNonNull(questId, "questId");
+        Objects.requireNonNull(issuerId, "issuerId");
+        Objects.requireNonNull(cancelledAt, "cancelledAt");
+        Quest active = state.quests().get(questId);
+        if (active == null) {
+            throw new IllegalArgumentException("Quest not found: " + questId);
+        }
+        if (!active.issuerId().equals(issuerId)) {
+            throw new IllegalArgumentException("Only the quest issuer can cancel this quest.");
+        }
+        if (active.status() != QuestStatus.ACTIVE || !cancelledAt.isBefore(active.expiresAt())) {
+            throw new IllegalStateException("That quest is no longer active or has expired.");
+        }
+
+        Quest cancelled = new Quest(
+            active.id(), active.issuerId(), active.issuerName(), active.requestedMaterial(),
+            active.requestedAmount(), active.reward(), active.createdAt(), active.expiresAt(),
+            QuestStatus.CANCELLED
+        );
+        QuestClaim claim = new QuestClaim(
+            UUID.randomUUID(), active.id(), active.issuerId(), active.reward(), cancelledAt
+        );
+        Map<UUID, Quest> quests = new LinkedHashMap<>(state.quests());
+        quests.put(active.id(), cancelled);
+        Map<UUID, List<QuestClaim>> claims = new LinkedHashMap<>(state.claims());
+        List<QuestClaim> ownerClaims = new ArrayList<>(
+            claims.getOrDefault(active.issuerId(), List.of())
+        );
+        ownerClaims.add(claim);
+        claims.put(active.issuerId(), ownerClaims);
+        save(new QuestState(quests, claims, state.notifications()));
+        return claim;
+    }
+
     synchronized List<IssuerNotification> pendingNotifications(UUID recipientId) {
         Objects.requireNonNull(recipientId, "recipientId");
         return state.notifications().values().stream()

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

@@ -38,13 +38,16 @@ public final class SpigotQuestBoardPlugin extends JavaPlugin {
         QuestCompletionGateway completer = new QuestCompletionController(
             quests, new BukkitQuestCompletionInventory(), notifier
         );
-        QuestCommand questCommand = new QuestCommand(creator, quests, completer, clock);
+        QuestCancellationGateway canceller = new QuestCancellationController(quests);
+        QuestCommand questCommand = new QuestCommand(
+            creator, quests, completer, canceller, clock
+        );
         command("quests").setExecutor(questCommand);
         command("quests").setTabCompleter(questCommand);
         getServer().getPluginManager().registerEvents(notifier, this);
         getServer().getPluginManager().registerEvents(
             new QuestBoardInteractionListener(
-                boards, new QuestBoardDialogUi(creator, quests, completer, clock)
+                boards, new QuestBoardDialogUi(creator, quests, completer, canceller, clock)
             ),
             this
         );