- Fixed a little loophole in the MustBlock code.

- First steps towards an AI for AF MustBlock.

src/main/java/forge/ComputerUtil_Block2.java

@@ -651,7 +651,8 @@ public class ComputerUtil_Block2 {
             if (!blocker.getMustBlockCards().isEmpty()) {
                 ArrayList<Card> blocks = blocker.getMustBlockCards();
                 for (Card attacker : blocks) {
-                    if (attacker.isAttacking() && CombatUtil.canBlock(attacker, blocker)) {
+                    if (attacker.isAttacking() && CombatUtil.canBlock(attacker, blocker, combat) 
+                            && getBlockersLeft().contains(blocker)) {
                         combat.addBlocker(attacker, blocker);
                         getBlockersLeft().remove(blocker);
                     }

src/main/java/forge/card/abilityFactory/AbilityFactory_Combat.java

@@ -5,10 +5,13 @@ import java.util.HashMap;
 
 import forge.AllZone;
 import forge.Card;
+import forge.CardList;
+import forge.CardListFilter;
 import forge.CombatUtil;
 import forge.ComputerUtil;
 import forge.Constant;
 import forge.Player;
+import forge.Constant.Zone;
 import forge.card.cardFactory.CardFactoryUtil;
 import forge.card.spellability.Ability_Activated;
 import forge.card.spellability.Ability_Sub;
@@ -835,17 +838,46 @@ public final class AbilityFactory_Combat {
     }
 
     private static boolean mustBlockDoTriggerAI(final AbilityFactory af, final SpellAbility sa,
-            final boolean mandatory)
+            final boolean mandatory) {
-    {
+        final Card source = sa.getSourceCard();
+        Target abTgt = sa.getTarget();
+        
         // If there is a cost payment it's usually not mandatory
         if (!ComputerUtil.canPayCost(sa) && !mandatory) {
             return false;
         }
+        
+        //only use on creatures that attack
+        if (!source.isAttacking())
+            return false;
 
-        boolean chance;
+        boolean chance = false;
 
-        //TODO - implement AI
+        CardList list = AllZone.getHumanPlayer().getCardsIn(Zone.Battlefield).getType("Creature");
-        chance = false;
+        list = list.getTargetableCards(source);
+        
+        if (abTgt != null) {
+            list = list.getValidCards(abTgt.getValidTgts(), source.getController(), source);
+            list = list.filter(new CardListFilter() {
+                public boolean addCard(Card c) {
+                    if (!CombatUtil.canBlock(source, c, AllZone.getCombat()))
+                        return false;
+                    if (CombatUtil.canDestroyAttacker(source, c, AllZone.getCombat(), false))
+                        return false;
+                    if (!CombatUtil.canDestroyBlocker(c, source, AllZone.getCombat(), false))
+                        return false;
+                    return true;
+                }
+            });
+            if (!list.isEmpty()) {
+                Card blocker = CardFactoryUtil.AI_getBestCreature(list);
+                if (blocker == null)
+                    return false;
+                abTgt.addTarget(CardFactoryUtil.AI_getBestCreature(list));
+                chance = false; //TODO:change this to true, once the human input takes mustblocks into account
+            }
+        } else
+            return false;
 
         // check SubAbilities DoTrigger?
         Ability_Sub abSub = sa.getSubAbility();

src/main/java/forge/card/cardFactory/CardFactoryUtil.java

@@ -4973,13 +4973,13 @@ public class CardFactoryUtil {
         }
         
         if(card.hasKeyword("Provoke")) {
-            String actualTrigger = "Mode$ Attacks | ValidCard$ Card.Self | OptionalDecider$ You | Execute$ UntapAbility | Secondary$ True | TriggerDescription$ When this attacks, you may have target creature defending player controls untap and block it if able.";
+            String actualTrigger = "Mode$ Attacks | ValidCard$ Card.Self | OptionalDecider$ You | Execute$ ProvokeAbility | Secondary$ True | TriggerDescription$ When this attacks, you may have target creature defending player controls untap and block it if able.";
-            String abString = "AB$ Untap | Cost$ 0 | ValidTgts$ Creature.YouDontCtrl | TgtPrompt$ Select target creature defending player controls | SubAbility$ DBProvoke";
+            String abString = "DB$ MustBlock | ValidTgts$ Creature.YouDontCtrl | TgtPrompt$ Select target creature defending player controls | SubAbility$ DBUntap";
-            String dbString = "DB$ MustBlock | Defined$ Targeted";
+            String dbString = "DB$ Untap | Defined$ Targeted";
             Trigger parsedTrigger = TriggerHandler.parseTrigger(actualTrigger, card, false);
             card.addTrigger(parsedTrigger);
-            card.setSVar("UntapAbility", abString);
+            card.setSVar("ProvokeAbility", abString);
-            card.setSVar("DBProvoke", dbString);
+            card.setSVar("DBUntap", dbString);
         }
 
         return card;