[DMU] Implemented Impede Momentum (#9383)

Mage/src/main/java/mage/abilities/effects/keyword/StunCounterEffect.java

@@ -0,0 +1,52 @@
+package mage.abilities.effects.keyword;
+
+import mage.abilities.Ability;
+import mage.abilities.effects.ReplacementEffectImpl;
+import mage.constants.Duration;
+import mage.constants.Outcome;
+import mage.counters.CounterType;
+import mage.game.Game;
+import mage.game.events.GameEvent;
+import mage.game.permanent.Permanent;
+
+/**
+ * @author TheElk801
+ */
+public class StunCounterEffect extends ReplacementEffectImpl {
+
+    public StunCounterEffect() {
+        super(Duration.Custom, Outcome.Tap);
+        this.staticText = "If a permanent with a stun counter would become untapped, remove one from it instead.";
+    }
+
+    private StunCounterEffect(final StunCounterEffect effect) {
+        super(effect);
+    }
+
+    @Override
+    public StunCounterEffect copy() {
+        return new StunCounterEffect(this);
+    }
+
+    @Override
+    public boolean replaceEvent(GameEvent event, Ability source, Game game) {
+        Permanent permanent = game.getPermanent(event.getTargetId());
+        if (permanent == null || permanent.getCounters(game).getCount(CounterType.STUN) < 1) {
+            return false;
+        }
+        permanent.removeCounters(CounterType.STUN.getName(), 1, source, game);
+        game.informPlayers("Removed a stun counter from " + permanent.getLogName());
+        return true;
+    }
+
+    @Override
+    public boolean checksEventType(GameEvent event, Game game) {
+        return event.getType() == GameEvent.EventType.UNTAP;
+    }
+
+    @Override
+    public boolean applies(GameEvent event, Ability source, Game game) {
+        Permanent permanent = game.getPermanent(event.getTargetId());
+        return permanent != null && permanent.getCounters(game).getCount(CounterType.STUN) > 0;
+    }
+}