[TLE] Implement Tale of Momo

Mage/src/main/java/mage/abilities/condition/common/CreatureLeftThisTurnCondition.java

@@ -0,0 +1,30 @@
+package mage.abilities.condition.common;
+
+import mage.abilities.Ability;
+import mage.abilities.condition.Condition;
+import mage.abilities.hint.ConditionHint;
+import mage.abilities.hint.Hint;
+import mage.game.Game;
+import mage.watchers.common.CreatureLeftBattlefieldWatcher;
+
+/**
+ * @author TheElk801
+ */
+public enum CreatureLeftThisTurnCondition implements Condition {
+    instance;
+    private static final Hint hint = new ConditionHint(instance);
+
+    public static Hint getHint() {
+        return hint;
+    }
+
+    @Override
+    public boolean apply(Game game, Ability source) {
+        return CreatureLeftBattlefieldWatcher.getNumberCreatureLeft(source.getControllerId(), game) > 0;
+    }
+
+    @Override
+    public String toString() {
+        return "a creature left the battlefield under your control this turn";
+    }
+}

Mage/src/main/java/mage/watchers/common/CreatureLeftBattlefieldWatcher.java

@@ -0,0 +1,51 @@
+package mage.watchers.common;
+
+import mage.constants.WatcherScope;
+import mage.constants.Zone;
+import mage.game.Game;
+import mage.game.events.GameEvent;
+import mage.game.events.ZoneChangeEvent;
+import mage.util.CardUtil;
+import mage.watchers.Watcher;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+
+/**
+ * @author Susucr
+ */
+public class CreatureLeftBattlefieldWatcher extends Watcher {
+
+    // player -> number of creatures that left the battlefield under that player's control this turn
+    private final Map<UUID, Integer> mapCreaturesLeft = new HashMap<>();
+
+    public CreatureLeftBattlefieldWatcher() {
+        super(WatcherScope.GAME);
+    }
+
+    @Override
+    public void watch(GameEvent event, Game game) {
+        if (event.getType() != GameEvent.EventType.ZONE_CHANGE) {
+            return;
+        }
+        ZoneChangeEvent zEvent = (ZoneChangeEvent) event;
+        if (Zone.BATTLEFIELD.match(zEvent.getFromZone()) && zEvent.getTarget().isCreature(game)) {
+            mapCreaturesLeft.compute(zEvent.getTarget().getControllerId(), CardUtil::setOrIncrementValue);
+        }
+    }
+
+    @Override
+    public void reset() {
+        super.reset();
+        mapCreaturesLeft.clear();
+    }
+
+    public static int getNumberCreatureLeft(UUID playerId, Game game) {
+        return game
+                .getState()
+                .getWatcher(CreatureLeftBattlefieldWatcher.class)
+                .mapCreaturesLeft
+                .getOrDefault(playerId, 0);
+    }
+}