feat(tamer): limit custody to one mob

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

@@ -2,7 +2,8 @@ package games.dmg.spigottyrant;
 
 import org.bukkit.entity.Player;
 
-@FunctionalInterface
 public interface CapturedMobCustodyRelease {
     PlayerState releaseAll(Player player, PlayerState state);
+
+    PlayerState releaseExcess(Player player, PlayerState state, int custodyLimit);
 }

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

@@ -16,6 +16,11 @@ public final class CapturedMobService {
         if (player.tyrantClass() != TyrantClass.TAMER) {
             throw new IllegalStateException("only a Tamer can capture mobs");
         }
+        if (!player.capturedMobs().isEmpty()) {
+            throw new IllegalStateException(
+                "release the currently captured mob before capturing another"
+            );
+        }
         if ("ENDER_DRAGON".equalsIgnoreCase(entityType)) {
             throw new IllegalArgumentException("Ender Dragons cannot be captured");
         }

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

@@ -13,13 +13,27 @@ public final class DefaultCapturedMobCustodyRelease implements CapturedMobCustod
 
     @Override
     public PlayerState releaseAll(Player player, PlayerState state) {
+        return releaseExcess(player, state, 0);
+    }
+
+    @Override
+    public PlayerState releaseExcess(
+        Player player,
+        PlayerState state,
+        int custodyLimit
+    ) {
+        if (custodyLimit < 0) {
+            throw new IllegalArgumentException("custodyLimit must not be negative");
+        }
         List<CapturedMob> retained = new ArrayList<>();
-        for (CapturedMob mob : state.capturedMobs()) {
-            if (!spawner.spawn(player, mob)) {
+        List<CapturedMob> custody = state.capturedMobs();
+        for (int index = 0; index < custody.size(); index++) {
+            CapturedMob mob = custody.get(index);
+            if (index < custodyLimit || !spawner.spawn(player, mob)) {
                 retained.add(mob);
             }
         }
-        if (retained.size() == state.capturedMobs().size()) {
+        if (retained.equals(custody)) {
             return state;
         }
         return new PlayerState(

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

@@ -37,14 +37,18 @@ public final class FormerTamerReleaseTask implements Runnable {
         Map<UUID, Player> online = server.getOnlinePlayers().stream()
             .collect(Collectors.toMap(Player::getUniqueId, player -> player));
         for (PlayerState state : stateManager.players().values()) {
-            if (state.tyrantClass() == TyrantClass.TAMER || state.capturedMobs().isEmpty()) {
+            if (state.capturedMobs().isEmpty()
+                    || state.tyrantClass() == TyrantClass.TAMER
+                        && state.capturedMobs().size() == 1) {
                 continue;
             }
             Player player = online.get(state.playerId());
             if (player == null || player.isDead()) {
                 continue;
             }
-            PlayerState released = release.releaseAll(player, state);
+            PlayerState released = state.tyrantClass() == TyrantClass.TAMER
+                ? release.releaseExcess(player, state, 1)
+                : release.releaseAll(player, state);
             if (released.equals(state)) {
                 continue;
             }

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

@@ -63,6 +63,11 @@ public final class TamerListener implements Listener {
             return;
         }
         PlayerState state = stateManager.player(player.getUniqueId(), player.getName());
+        if (!state.capturedMobs().isEmpty()) {
+            player.sendMessage(ChatColor.RED
+                + "Release the currently captured mob before capturing another.");
+            return;
+        }
         Entity target = event.getRightClicked();
         if (!canCapture(state, target)) {
             player.sendMessage(ChatColor.RED + "That mob cannot be captured.");

src/test/java/games/dmg/spigottyrant/CapturedMobServiceTest.java

@@ -28,6 +28,21 @@ final class CapturedMobServiceTest {
         assertEquals(java.util.List.of(), released.capturedMobs());
     }
 
+    @Test
+    void tamerMustReleaseHeldMobBeforeCapturingAnother() {
+        PlayerState holding = service.capture(
+            tamer(), UUID.randomUUID(), "COW", "cow-snapshot"
+        );
+
+        IllegalStateException exception = assertThrows(IllegalStateException.class, () ->
+            service.capture(holding, UUID.randomUUID(), "SHEEP", "sheep-snapshot")
+        );
+
+        assertEquals("release the currently captured mob before capturing another",
+            exception.getMessage());
+        assertEquals(1, holding.capturedMobs().size());
+    }
+
     @Test
     void enderDragonCanNeverBeCapturedAndMissingReleaseDoesNotMutate() {
         assertThrows(IllegalArgumentException.class, () -> service.capture(

src/test/java/games/dmg/spigottyrant/DefaultCapturedMobCustodyReleaseTest.java

@@ -12,6 +12,28 @@ import org.bukkit.entity.Player;
 import org.junit.jupiter.api.Test;
 
 final class DefaultCapturedMobCustodyReleaseTest {
+    @Test
+    void legacyExcessReleaseRetainsOneAndAnyFailedExtra() {
+        UUID playerId = UUID.fromString("33333333-3333-3333-3333-333333333333");
+        CapturedMob retained = mob("COW");
+        CapturedMob releasedExtra = mob("SHEEP");
+        CapturedMob deferredExtra = mob("PIG");
+        PlayerState state = new PlayerState(
+            playerId, "Tamer", Optional.empty(), Optional.empty(), TyrantClass.TAMER,
+            Optional.empty(), Map.of(), java.util.Set.of(),
+            List.of(retained, releasedExtra, deferredExtra)
+        );
+        CapturedMobSpawner spawner = mock(CapturedMobSpawner.class);
+        Player player = mock(Player.class);
+        when(spawner.spawn(player, releasedExtra)).thenReturn(true);
+        when(spawner.spawn(player, deferredExtra)).thenReturn(false);
+        DefaultCapturedMobCustodyRelease service = new DefaultCapturedMobCustodyRelease(spawner);
+
+        PlayerState result = service.releaseExcess(player, state, 1);
+
+        assertEquals(List.of(retained, deferredExtra), result.capturedMobs());
+    }
+
     @Test
     void removesOnlyCustodyThatSpawnedSuccessfully() {
         UUID playerId = UUID.fromString("33333333-3333-3333-3333-333333333333");

src/test/java/games/dmg/spigottyrant/FormerTamerReleaseTaskTest.java

@@ -31,6 +31,28 @@ final class FormerTamerReleaseTaskTest {
         verify(release, never()).releaseAll(any(), any());
     }
 
+    @Test
+    void safelyReleasesLegacyCustodyAboveOneForActiveTamer() {
+        UUID tamerId = UUID.fromString("44444444-4444-4444-4444-444444444444");
+        PlayerState once = withMob(withClass(
+            PlayerState.newPlayer(tamerId, "Tamer"), TyrantClass.TAMER
+        ));
+        PlayerState legacy = withMob(once);
+        TyrantStateManager manager = mock(TyrantStateManager.class);
+        when(manager.players()).thenReturn(Map.of(tamerId, legacy));
+        Player tamer = mock(Player.class);
+        when(tamer.getUniqueId()).thenReturn(tamerId);
+        Server server = mock(Server.class);
+        doReturn(Set.of(tamer)).when(server).getOnlinePlayers();
+        CapturedMobCustodyRelease release = mock(CapturedMobCustodyRelease.class);
+        when(release.releaseExcess(tamer, legacy, 1)).thenReturn(legacy);
+
+        new FormerTamerReleaseTask(manager, server, release).run();
+
+        verify(release).releaseExcess(tamer, legacy, 1);
+        verify(release, never()).releaseAll(any(), any());
+    }
+
     @Test
     void releasesCustodyOnlyAfterPlayerLosesTamerClass() {
         UUID formerId = UUID.fromString("33333333-3333-3333-3333-333333333333");
@@ -61,10 +83,12 @@ final class FormerTamerReleaseTaskTest {
         CapturedMob mob = new CapturedMob("COW", Map.of(
             "capture-id", UUID.randomUUID().toString(), "snapshot", "snapshot"
         ));
+        java.util.List<CapturedMob> custody = new java.util.ArrayList<>(player.capturedMobs());
+        custody.add(mob);
         return new PlayerState(
             player.playerId(), player.latestName(), player.lastLogin(), player.optedOutUntil(),
             player.tyrantClass(), player.followerOf(), player.cooldownEnds(),
-            player.readyAbilityItems(), java.util.List.of(mob)
+            player.readyAbilityItems(), custody
         );
     }
 

src/test/java/games/dmg/spigottyrant/TamerListenerTest.java

@@ -0,0 +1,66 @@
+package games.dmg.spigottyrant;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.UUID;
+import org.bukkit.Server;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.Player;
+import org.bukkit.event.player.PlayerInteractEntityEvent;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.PlayerInventory;
+import org.junit.jupiter.api.Test;
+
+final class TamerListenerTest {
+    @Test
+    void heldMobRejectsAnotherCaptureBeforeTargetOrInventoryChanges() {
+        UUID playerId = UUID.fromString("33333333-3333-3333-3333-333333333333");
+        CapturedMob heldMob = new CapturedMob("COW", Map.of(
+            "capture-id", UUID.randomUUID().toString(), "snapshot", "cow"
+        ));
+        PlayerState state = new PlayerState(
+            playerId, "Tamer", Optional.empty(), Optional.empty(), TyrantClass.TAMER,
+            Optional.empty(), Map.of(), Set.of(Ability.TAMER_CAPTURE),
+            java.util.List.of(heldMob)
+        );
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(playerId);
+        when(player.getName()).thenReturn("Tamer");
+        PlayerInventory inventory = mock(PlayerInventory.class);
+        when(player.getInventory()).thenReturn(inventory);
+        ItemStack lead = mock(ItemStack.class);
+        when(inventory.getItem(org.bukkit.inventory.EquipmentSlot.HAND)).thenReturn(lead);
+        Entity target = mock(Entity.class);
+        PlayerInteractEntityEvent event = mock(PlayerInteractEntityEvent.class);
+        when(event.getPlayer()).thenReturn(player);
+        when(event.getHand()).thenReturn(org.bukkit.inventory.EquipmentSlot.HAND);
+        when(event.getRightClicked()).thenReturn(target);
+        AbilityItemService abilityItems = mock(AbilityItemService.class);
+        when(abilityItems.ability(lead)).thenReturn(Optional.of(Ability.TAMER_CAPTURE));
+        when(abilityItems.owner(lead)).thenReturn(Optional.of(playerId));
+        TyrantStateManager manager = mock(TyrantStateManager.class);
+        when(manager.player(playerId, "Tamer")).thenReturn(state);
+        CapturedMobItemService capturedItems = mock(CapturedMobItemService.class);
+        TamerListener listener = new TamerListener(
+            manager, abilityItems, capturedItems, new CapturedMobService(),
+            PluginSettings.from(Map.of()), mock(Server.class)
+        );
+
+        listener.onCapture(event);
+
+        verify(player).sendMessage(org.mockito.ArgumentMatchers.contains(
+            "Release the currently captured mob"
+        ));
+        verify(target, never()).createSnapshot();
+        verify(capturedItems, never()).create(
+            org.mockito.ArgumentMatchers.any(), org.mockito.ArgumentMatchers.any(),
+            org.mockito.ArgumentMatchers.anyString()
+        );
+    }
+}