[NCC] Address comments for Lethal Scheme

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

@@ -0,0 +1,59 @@
+package mage.watchers.common;
+
+import mage.MageObjectReference;
+import mage.constants.WatcherScope;
+import mage.game.Game;
+import mage.game.events.GameEvent;
+import mage.game.permanent.Permanent;
+import mage.game.stack.Spell;
+import mage.watchers.Watcher;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * @author LevelX2
+ */
+public class EachCreatureThatConvokedSourceWatcher extends Watcher {
+
+    private final Map<MageObjectReference, Set<MageObjectReference>> convokingCreatures = new HashMap<>();
+
+    public EachCreatureThatConvokedSourceWatcher() {
+        super(WatcherScope.GAME);
+    }
+
+    @Override
+    public void watch(GameEvent event, Game game) {
+        if (event.getType() != GameEvent.EventType.CONVOKED) {
+            return;
+        }
+
+        Spell spell = game.getSpell(event.getSourceId());
+        Permanent tappedCreature = game.getPermanentOrLKIBattlefield(event.getTargetId());
+        if (spell == null || tappedCreature == null) {
+            return;
+        }
+
+        MageObjectReference convokedSpell = new MageObjectReference(spell.getSourceId(), game);
+        Set<MageObjectReference> creatures;
+        if (convokingCreatures.containsKey(convokedSpell)) {
+            creatures = convokingCreatures.get(convokedSpell);
+        } else {
+            creatures = new HashSet<>();
+            convokingCreatures.put(convokedSpell, creatures);
+        }
+        creatures.add(new MageObjectReference(tappedCreature, game));
+    }
+
+    public Set<MageObjectReference> getConvokingCreatures(MageObjectReference mor) {
+        return convokingCreatures.get(mor);
+    }
+
+    @Override
+    public void reset() {
+        super.reset();
+        convokingCreatures.clear();
+    }
+}