- ChangeCombatantsEffect: attempt to account for the new rule for Ulamog, the Ceaseless Hunger + Portal Mage interaction in multiplayer games. Currently achieved by rigging the triggering info on the stack instance, which may not be optimal. Feel free to propose a better solution.

forge-game/src/main/java/forge/game/ability/effects/ChangeCombatantsEffect.java

@@ -7,7 +7,9 @@ import forge.game.card.Card;
 import forge.game.combat.AttackingBand;
 import forge.game.combat.Combat;
 import forge.game.event.GameEventCombatChanged;
+import forge.game.player.Player;
 import forge.game.spellability.SpellAbility;
+import forge.game.spellability.SpellAbilityStackInstance;
 import forge.game.spellability.TargetRestrictions;
 import forge.util.collect.FCollectionView;
 
@@ -38,17 +40,29 @@ public class ChangeCombatantsEffect extends SpellAbilityEffect {
         for (final Card c : getTargetCards(sa)) {
             if ((tgt == null) || c.canBeTargetedBy(sa)) {
                 final Combat combat = game.getCombat();
-                final GameEntity orginalDefender = combat.getDefenderByAttacker(c);
+                final GameEntity originalDefender = combat.getDefenderByAttacker(c);
                 final FCollectionView<GameEntity> defs = combat.getDefenders();
                 final GameEntity defender = sa.getActivatingPlayer().getController().chooseSingleEntityForEffect(defs, sa,
                         "Choose which defender to attack with " + c, false);
-                if (orginalDefender != null && !orginalDefender.equals(defender)) {
+                if (originalDefender != null && !originalDefender.equals(defender)) {
                     AttackingBand ab = combat.getBandOfAttacker(c);
                     if (ab != null) {
                         combat.unregisterAttacker(c, ab);
                         ab.removeAttacker(c);
                     }
                     combat.addAttacker(c, defender);
+                    // retarget triggers to the new defender (e.g. Ulamog, Ceaseless Hunger + Portal Mage)
+                    for (SpellAbilityStackInstance si : game.getStack()) {
+                        if (si.isTrigger() && c.equals(si.getSourceCard())
+                                && si.getTriggeringObject("Attacker") != null) {
+                            si.addTriggeringObject("OriginalDefender", originalDefender);
+                            if (defender instanceof Player) {
+                                si.updateTriggeringObject("DefendingPlayer", defender);
+                            } else if (defender instanceof Card) {
+                                si.updateTriggeringObject("DefendingPlayer", ((Card)defender).getController());
+                            }
+                        }
+                    }
                     isCombatChanged = true;
                 }
             }

forge-game/src/main/java/forge/game/combat/Combat.java

@@ -24,6 +24,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 
+import forge.game.Game;
+import forge.game.spellability.SpellAbilityStackInstance;
 import org.apache.commons.lang3.tuple.Pair;
 
 import com.google.common.base.Function;
@@ -541,6 +543,24 @@ public class Combat {
                 }
             }
         }
+
+        // restore the original defender in case it was changed before the creature was
+        // removed from combat but before the trigger resolved (e.g. Ulamog, the Ceaseless
+        // Hunger + Portal Mage + Unsummon)
+        Game game = c.getGame();
+        for (SpellAbilityStackInstance si : game.getStack()) {
+            if (si.isTrigger() && c.equals(si.getSourceCard())) {
+                GameEntity origDefender = (GameEntity)si.getTriggeringObject("OriginalDefender");
+                if (origDefender != null) {
+                    si.updateTriggeringObject("Defender", origDefender);
+                    if (origDefender instanceof Player) {
+                        si.updateTriggeringObject("DefendingPlayer", origDefender);
+                    } else if (origDefender instanceof Card) {
+                        si.updateTriggeringObject("DefendingPlayer", ((Card)origDefender).getController());
+                    }
+                }
+            }
+        }
     }
 
     // removes references to this defender from all indices and orders

forge-game/src/main/java/forge/game/spellability/SpellAbilityStackInstance.java

@@ -356,6 +356,29 @@ public class SpellAbilityStackInstance implements IIdentifiable, IHasCardView {
         }
     }
 
+    public boolean addTriggeringObject(String trigObj, Object value) {
+        if (!triggeringObjects.containsKey(trigObj)) {
+            triggeringObjects.put(trigObj, value);
+            return true;
+        }
+        return false;
+    }
+
+    public boolean updateTriggeringObject(String trigObj, Object value) {
+        if (triggeringObjects.containsKey(trigObj)) {
+            triggeringObjects.replace(trigObj, value);
+            return true;
+        }
+        return false;
+    }
+
+    public Object getTriggeringObject(String trigObj) {
+        if (triggeringObjects.containsKey(trigObj)) {
+            return triggeringObjects.get(trigObj);
+        }
+        return null;
+    }
+
     public boolean compareToSpellAbility(SpellAbility sa) {
         // Compare my target choices to the SA passed in
         // TODO? Compare other data points in the SI to the passed SpellAbility for confirmation