feat(quests): add issuer quest cancellation

src/test/java/games/dmg/spigotquestboard/QuestBoardDialogUiTest.java

@@ -52,6 +52,41 @@ final class QuestBoardDialogUiTest {
         assertEquals(NOW, completer.completedAt);
     }
 
+    @Test
+    void cancellationActionUsesEquivalentCancellationFlow() {
+        RecordingCreator creator = new RecordingCreator(false);
+        RecordingCanceller canceller = new RecordingCanceller();
+        QuestBoardDialogUi ui = new QuestBoardDialogUi(
+            creator, now -> List.of(), null, canceller, Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player player = mock(Player.class);
+        String id = UUID.randomUUID().toString();
+
+        ui.submitCancellation(player, id);
+
+        assertEquals(player, canceller.player);
+        assertEquals(id, canceller.questId);
+        assertEquals(NOW, canceller.cancelledAt);
+    }
+
+    @Test
+    void boardOnlyOffersCancellationActionsForPlayersOwnedActiveQuests() {
+        RecordingCreator creator = new RecordingCreator(false);
+        Quest owned = creator.quest(NOW);
+        Quest other = new Quest(
+            UUID.randomUUID(), UUID.randomUUID(), "Other", "DIRT", 1,
+            List.of(new EscrowItem("COAL", 1, null)), NOW, NOW.plusSeconds(604800)
+        );
+        QuestBoardDialogUi ui = new QuestBoardDialogUi(
+            creator, now -> List.of(owned, other), null, new RecordingCanceller(),
+            Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player issuer = mock(Player.class);
+        org.mockito.Mockito.when(issuer.getUniqueId()).thenReturn(owned.issuerId());
+
+        assertEquals(List.of(owned.id().toString()), ui.cancellableQuestIds(issuer));
+    }
+
     @Test
     void everyOpeningBuildsAListingFromTheCurrentActiveQuests() {
         RecordingCreator creator = new RecordingCreator(false);
@@ -77,6 +112,20 @@ final class QuestBoardDialogUiTest {
         );
     }
 
+    private static final class RecordingCanceller implements QuestCancellationGateway {
+        private Player player;
+        private String questId;
+        private Instant cancelledAt;
+
+        @Override
+        public QuestClaim cancel(Player cancellingPlayer, String id, Instant instant) {
+            player = cancellingPlayer;
+            questId = id;
+            cancelledAt = instant;
+            return null;
+        }
+    }
+
     private static final class RecordingCompleter implements QuestCompletionGateway {
         private Player player;
         private String questId;

src/test/java/games/dmg/spigotquestboard/QuestCancellationControllerTest.java

@@ -0,0 +1,58 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.contains;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+
+final class QuestCancellationControllerTest {
+    @Test
+    void cancelsAsPlayerIdentityAndCreatesClaimWithoutInventorySettlement() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = service.create(
+            issuer, "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 2, "exact-data")), Instant.EPOCH
+        );
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(issuer);
+
+        QuestClaim claim = new QuestCancellationController(service).cancel(
+            player, quest.id().toString(), Instant.EPOCH.plusSeconds(1)
+        );
+
+        assertEquals(quest.reward(), claim.items());
+        assertEquals(List.of(claim), service.state().claims().get(issuer));
+        verify(player).sendMessage(contains("claim"));
+    }
+
+    @Test
+    void rejectsMalformedQuestIdentifier() throws Exception {
+        QuestCancellationController controller = new QuestCancellationController(
+            new QuestService(new Repository())
+        );
+
+        IllegalArgumentException exception = assertThrows(
+            IllegalArgumentException.class,
+            () -> controller.cancel(mock(Player.class), "not-a-uuid", Instant.EPOCH)
+        );
+
+        assertEquals("Quest identifier must be a valid UUID.", exception.getMessage());
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        @Override public QuestState load() { return state; }
+        @Override public void save(QuestState candidate) throws IOException { state = candidate; }
+    }
+}

src/test/java/games/dmg/spigotquestboard/QuestCancellationServiceTest.java

@@ -0,0 +1,159 @@
+package games.dmg.spigotquestboard;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import org.junit.jupiter.api.Test;
+
+final class QuestCancellationServiceTest {
+    @Test
+    void onlyIssuerCanCancelAndExactRewardBecomesClaim() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        EscrowItem reward = new EscrowItem("DIAMOND", 3, "exact-item-data");
+        Quest quest = service.create(
+            issuer, "Issuer", "STONE", 64, List.of(reward), Instant.EPOCH
+        );
+
+        assertThrows(IllegalArgumentException.class, () -> service.cancel(
+            quest.id(), UUID.randomUUID(), Instant.EPOCH.plusSeconds(1)
+        ));
+        QuestClaim claim = service.cancel(
+            quest.id(), issuer, Instant.EPOCH.plusSeconds(1)
+        );
+
+        assertEquals(QuestStatus.CANCELLED, service.state().quests().get(quest.id()).status());
+        assertEquals(List.of(reward), claim.items());
+        assertEquals(List.of(claim), service.state().claims().get(issuer));
+        assertTrue(service.activeQuests(Instant.EPOCH.plusSeconds(1)).isEmpty());
+    }
+
+    @Test
+    void completedCancelledAndExpiredQuestsCannotBeCancelled() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest completed = quest(service, issuer);
+        service.complete(
+            completed.id(), new EscrowItem("STONE", 1, null), Instant.EPOCH.plusSeconds(1)
+        );
+        Quest cancelled = quest(service, issuer);
+        service.cancel(cancelled.id(), issuer, Instant.EPOCH.plusSeconds(1));
+        Quest expired = quest(service, issuer);
+
+        assertThrows(IllegalStateException.class, () -> service.cancel(
+            completed.id(), issuer, Instant.EPOCH.plusSeconds(2)
+        ));
+        assertThrows(IllegalStateException.class, () -> service.cancel(
+            cancelled.id(), issuer, Instant.EPOCH.plusSeconds(2)
+        ));
+        assertThrows(IllegalStateException.class, () -> service.cancel(
+            expired.id(), issuer, expired.expiresAt()
+        ));
+    }
+
+    @Test
+    void persistenceFailureLeavesQuestActiveAndRewardEscrowed() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = quest(service, issuer);
+        QuestState before = service.state();
+        repository.fail = true;
+
+        assertThrows(IOException.class, () -> service.cancel(
+            quest.id(), issuer, Instant.EPOCH.plusSeconds(1)
+        ));
+
+        assertEquals(before, service.state());
+        assertEquals(before, repository.state);
+        assertEquals(QuestStatus.ACTIVE, service.state().quests().get(quest.id()).status());
+        assertTrue(service.state().claims().isEmpty());
+    }
+
+    @Test
+    void simultaneousCancellationAndCompletionSettleEscrowExactlyOnce() throws Exception {
+        Repository repository = new Repository();
+        QuestService service = new QuestService(repository);
+        UUID issuer = UUID.randomUUID();
+        Quest quest = quest(service, issuer);
+        CountDownLatch start = new CountDownLatch(1);
+        try (ExecutorService executor = Executors.newFixedThreadPool(2)) {
+            List<Future<Boolean>> attempts = new ArrayList<>();
+            attempts.add(executor.submit(() -> {
+                start.await();
+                try {
+                    service.cancel(quest.id(), issuer, Instant.EPOCH.plusSeconds(1));
+                    return true;
+                } catch (IllegalStateException exception) {
+                    return false;
+                }
+            }));
+            attempts.add(executor.submit(() -> {
+                start.await();
+                try {
+                    service.complete(
+                        quest.id(), new EscrowItem("STONE", 1, null),
+                        Instant.EPOCH.plusSeconds(1)
+                    );
+                    return true;
+                } catch (IllegalStateException exception) {
+                    return false;
+                }
+            }));
+            start.countDown();
+            assertEquals(1, attempts.stream().filter(attempt -> {
+                try {
+                    return attempt.get();
+                } catch (Exception exception) {
+                    throw new AssertionError(exception);
+                }
+            }).count());
+        }
+
+        QuestStatus status = service.state().quests().get(quest.id()).status();
+        assertTrue(status == QuestStatus.CANCELLED || status == QuestStatus.COMPLETED);
+        assertEquals(1, service.state().claims().get(issuer).size());
+        QuestClaim settlement = service.state().claims().get(issuer).getFirst();
+        if (status == QuestStatus.CANCELLED) {
+            assertEquals(quest.reward(), settlement.items());
+            assertTrue(service.state().notifications().isEmpty());
+        } else {
+            assertEquals(List.of(new EscrowItem("STONE", 1, null)), settlement.items());
+            assertEquals(1, service.state().notifications().size());
+        }
+    }
+
+    private static Quest quest(QuestService service, UUID issuer) throws IOException {
+        return service.create(
+            issuer, "Issuer", "STONE", 1,
+            List.of(new EscrowItem("DIAMOND", 2, null)), Instant.EPOCH
+        );
+    }
+
+    private static final class Repository implements QuestRepository {
+        private QuestState state = QuestState.empty();
+        private boolean fail;
+
+        @Override public QuestState load() { return state; }
+
+        @Override
+        public void save(QuestState candidate) throws IOException {
+            if (fail) {
+                throw new IOException("disk full");
+            }
+            state = candidate;
+        }
+    }
+}

src/test/java/games/dmg/spigotquestboard/QuestCommandTest.java

@@ -105,6 +105,25 @@ final class QuestCommandTest {
         assertEquals(NOW, completer.completedAt);
     }
 
+    @Test
+    void cancelCommandRoutesPlayerAndCurrentTimeToEquivalentGateway() {
+        RecordingCreator creator = new RecordingCreator();
+        RecordingCanceller canceller = new RecordingCanceller();
+        QuestCommand executor = new QuestCommand(
+            creator, now -> List.of(), null, canceller, Clock.fixed(NOW, ZoneOffset.UTC)
+        );
+        Player player = mock(Player.class);
+        String id = UUID.randomUUID().toString();
+
+        assertTrue(executor.onCommand(
+            player, mock(Command.class), "quests", new String[] {"cancel", id}
+        ));
+
+        assertEquals(player, canceller.player);
+        assertEquals(id, canceller.questId);
+        assertEquals(NOW, canceller.cancelledAt);
+    }
+
     @Test
     void questIdentifierAutocompleteOnlyUsesActiveAndOwnedQuests() {
         RecordingCreator creator = new RecordingCreator();
@@ -139,6 +158,8 @@ final class QuestCommandTest {
             executor.onTabComplete(player, command, "quests", new String[] {"cr"}));
         assertEquals(List.of("list"),
             executor.onTabComplete(player, command, "quests", new String[] {"li"}));
+        assertEquals(List.of("cancel"),
+            executor.onTabComplete(player, command, "quests", new String[] {"ca"}));
         assertEquals(List.of("STONE", "STONE_BRICKS"), executor.onTabComplete(
             player, command, "quests", new String[] {"create", "sto"}
         ));
@@ -159,6 +180,20 @@ final class QuestCommandTest {
         return new QuestCommand(creator, browser, Clock.fixed(NOW, ZoneOffset.UTC));
     }
 
+    private static final class RecordingCanceller implements QuestCancellationGateway {
+        private Player player;
+        private String questId;
+        private Instant cancelledAt;
+
+        @Override
+        public QuestClaim cancel(Player cancellingPlayer, String id, Instant instant) {
+            player = cancellingPlayer;
+            questId = id;
+            cancelledAt = instant;
+            return null;
+        }
+    }
+
     private static final class RecordingCompleter implements QuestCompletionGateway {
         private Player player;
         private String questId;