[STX] Implemented Waterfall Aerialist

Mage/src/main/java/mage/abilities/keyword/WardAbility.java

@@ -0,0 +1,54 @@
+package mage.abilities.keyword;
+
+import mage.abilities.TriggeredAbilityImpl;
+import mage.abilities.costs.Cost;
+import mage.abilities.effects.common.CounterUnlessPaysEffect;
+import mage.constants.Zone;
+import mage.game.Game;
+import mage.game.events.GameEvent;
+import mage.game.stack.StackObject;
+import mage.target.targetpointer.FixedTarget;
+
+/**
+ * @author TheElk801
+ */
+public class WardAbility extends TriggeredAbilityImpl {
+
+    public WardAbility(Cost cost) {
+        super(Zone.BATTLEFIELD, new CounterUnlessPaysEffect(cost), false);
+    }
+
+    private WardAbility(final WardAbility ability) {
+        super(ability);
+    }
+
+    @Override
+    public boolean checkEventType(GameEvent event, Game game) {
+        return event.getType() == GameEvent.EventType.TARGETED;
+    }
+
+    @Override
+    public boolean checkTrigger(GameEvent event, Game game) {
+        if (!getSourceId().equals(event.getTargetId())) {
+            return false;
+        }
+        StackObject stackObject = game.getStack().getStackObject(event.getSourceId());
+        if (stackObject == null || !game.getOpponents(getControllerId()).contains(stackObject.getControllerId())) {
+            return false;
+        }
+        getEffects().setTargetPointer(new FixedTarget(event.getSourceId(), game));
+        return true;
+    }
+
+    @Override
+    public WardAbility copy() {
+        return new WardAbility(this);
+    }
+
+    @Override
+    public String getRule() {
+        return "Ward " + this.getCosts().getText()
+                + " <i>(Whenever {this} becomes the target of a spell or ability an opponent controls, " +
+                "counter that spell or ability unless its controller pays " + this.getCosts().getText() + ")</i>";
+    }
+}