implement [EOE] Kav Landseeker; fix & test Meandering Towershell along the way

Mage/src/main/java/mage/abilities/common/delayed/AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility.java

@@ -0,0 +1,83 @@
+package mage.abilities.common.delayed;
+
+import mage.abilities.DelayedTriggeredAbility;
+import mage.abilities.effects.Effect;
+import mage.constants.Duration;
+import mage.game.Game;
+import mage.game.events.GameEvent;
+
+/**
+ * @author Susucr
+ */
+public class AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility extends DelayedTriggeredAbility {
+
+    private GameEvent.EventType stepEvent;
+    private int nextTurn = -1; // once the controller starts a new turn, register it to trigger that turn.
+    private boolean isActive = true;
+
+    public AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility(Effect effect, GameEvent.EventType stepEvent) {
+        this(effect, stepEvent, false);
+    }
+
+    public AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility(Effect effect, GameEvent.EventType stepEvent, boolean optional) {
+        super(effect, Duration.Custom, true, optional);
+        this.stepEvent = stepEvent;
+        this.setTriggerPhrase(generateTriggerPhrase());
+    }
+
+    private AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility(final AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility ability) {
+        super(ability);
+        this.nextTurn = ability.nextTurn;
+        this.isActive = ability.isActive;
+        this.stepEvent = ability.stepEvent;
+    }
+
+    @Override
+    public AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility copy() {
+        return new AtTheBeginOfStepOfYourNextTurnDelayedTriggeredAbility(this);
+    }
+
+    @Override
+    public boolean checkEventType(GameEvent event, Game game) {
+        return event.getType() == stepEvent
+                || event.getType() == GameEvent.EventType.BEGIN_TURN;
+    }
+
+    @Override
+    public boolean checkTrigger(GameEvent event, Game game) {
+        if (!isControlledBy(event.getPlayerId())) {
+            // not your turn.
+            return false;
+        }
+
+        int turn = game.getTurnNum();
+        switch (event.getType()) {
+            case BEGIN_TURN:
+                // We register the turn number at the start of your next turn.
+                // This is in order to not trigger if that turn ends without an end step.
+                if (this.nextTurn == -1) {
+                    this.nextTurn = turn;
+                } else if (turn > this.nextTurn) {
+                    this.isActive = false; // to have the delayed trigger being cleaned up
+                }
+                return false;
+            default:
+                return turn == this.nextTurn && event.getType() == stepEvent;
+        }
+    }
+
+    @Override
+    public boolean isInactive(Game game) {
+        return super.isInactive(game) || !isActive;
+    }
+
+    private String generateTriggerPhrase() {
+        switch (stepEvent) {
+            case END_TURN_STEP_PRE:
+                return "At the beginning of the end step on your next turn, ";
+            case DECLARE_ATTACKERS_STEP_PRE:
+                return "At the beginning of the declare attackers step on your next turn, ";
+        }
+        throw new IllegalArgumentException("stepEvent only supports steps events");
+    }
+}