Battle AI support + improve Battle mechanics support (#3107)

* - First draft of (very sketchy) Battle AI code.

* - Imports fix.

* - Slightly cleaner refreshCombatants.

* - Update Combat to allow the protecting player to participate in declaring blocks to defend a battle.

* - Update AiBlockController in order to allow the AI to participate in defending battles it's protecting.

* Clean up

* - Minor cleanup.

* Fix checking backside

* Add TODO

* Fix missing combat removal

* - Suggested minor cleanup.

* - Fix imports.

* - Improve support for battles in getAllPossibleDefenders.

* - AI: prefer own Battles before choosing allied Battles.

* Fix ClassCastException

---------

Co-authored-by: TRT <>

forge-ai/src/main/java/forge/ai/AiAttackController.java

@@ -119,7 +119,11 @@ public class AiAttackController {
     } // overloaded constructor to evaluate single specified attacker
 
     private void refreshCombatants(GameEntity defender) {
-        this.oppList = getOpponentCreatures(defendingOpponent);
+        if (defender instanceof Card && ((Card) defender).isBattle()) {
+            this.oppList = getOpponentCreatures(((Card) defender).getProtectingPlayer());
+        } else {
+            this.oppList = getOpponentCreatures(defendingOpponent);
+        }
         this.attackers = new ArrayList<>();
         for (Card c : myList) {
             if (canAttackWrapper(c, defender)) {
@@ -722,9 +726,14 @@ public class AiAttackController {
             return pwNearUlti != null ? pwNearUlti : ComputerUtilCard.getBestPlaneswalkerAI(pwDefending);
         }
 
-        List<Card> battleDefending = c.getDefendingBattles();
-        if (!battleDefending.isEmpty()) {
-            // TODO filter for team ones
+        // Get the preferred battle (prefer own battles, then ally battles)
+        final CardCollection defBattles = c.getDefendingBattles();
+        List<Card> ownBattleDefending = CardLists.filter(defBattles, CardPredicates.isController(ai));
+        List<Card> allyBattleDefending = CardLists.filter(defBattles, CardPredicates.isControlledByAnyOf(ai.getAllies()));
+        List<Card> prefBattleList = ownBattleDefending.isEmpty() ? allyBattleDefending : ownBattleDefending;
+        if (!prefBattleList.isEmpty()) {
+            // TODO try to be less predictable here, should really check if something would make the back uncastable
+            return Collections.min(prefBattleList, CardPredicates.compareByCounterType(CounterEnumType.DEFENSE));
         }
 
         return prefDefender;
@@ -756,7 +765,17 @@ public class AiAttackController {
         // decided to attack another defender so related lists need to be updated
         // (though usually rather try to avoid this situation for performance reasons)
         if (defender != defendingOpponent) {
-            defendingOpponent = defender instanceof Player ? (Player) defender : ((Card)defender).getController();
+            if (defender instanceof Player) {
+                defendingOpponent = (Player) defender;
+            } else if (defender instanceof Card) {
+                Card defCard = (Card) defender;
+                if (defCard.isBattle()) {
+                    defendingOpponent = defCard.getProtectingPlayer();
+                } else {
+                    // TODO: assume Planeswalker for now, may need to be updated later if more unique mechanics appear like Battle
+                    defendingOpponent = defCard.getController();
+                }
+            }
             refreshCombatants(defender);
         }
         if (this.attackers.isEmpty()) {

forge-ai/src/main/java/forge/ai/AiBlockController.java

@@ -165,10 +165,12 @@ public class AiBlockController {
         }
 
         // TODO Add creatures attacking Planeswalkers in order of which we want to protect
-        // defend planeswalkers with more loyalty before planeswalkers with less loyalty
-        // if planeswalker will be too difficult to defend don't even bother
+        // defend planeswalkers with more loyalty before planeswalkers with less loyalty,
+        // defend battles with fewer defense counters before battles with more defense counters,
+        // if planeswalker/battle will be too difficult to defend don't even bother
         for (GameEntity defender : defenders) {
-            if (defender instanceof Card && ((Card) defender).getController().equals(ai)) {
+            if ((defender instanceof Card && ((Card) defender).getController().equals(ai))
+                    || (defender instanceof Card && ((Card) defender).isBattle() && ((Card) defender).getProtectingPlayer().equals(ai))) {
                 final CardCollection attackers = combat.getAttackersOf(defender);
                 // Begin with the attackers that pose the biggest threat
                 CardLists.sortByPowerDesc(attackers);

forge-ai/src/main/java/forge/ai/ability/PlayAi.java

@@ -139,17 +139,25 @@ public class PlayAi extends SpellAbilityAi {
     @Override
     public Card chooseSingleCard(final Player ai, final SpellAbility sa, Iterable<Card> options,
             final boolean isOptional, Player targetedPlayer, Map<String, Object> params) {
+        final CardStateName state;
+        if (sa.hasParam("CastTransformed")) {
+            state = CardStateName.Transformed;
+            options.forEach(c -> c.changeToState(CardStateName.Transformed));
+        } else {
+            state = CardStateName.Original; 
+        }
+
         List<Card> tgtCards = CardLists.filter(options, new Predicate<Card>() {
             @Override
             public boolean apply(final Card c) {
                 // TODO needs to be aligned for MDFC along with getAbilityToPlay so the knowledge
                 // of which spell was the reason for the choice can be used there
-                for (SpellAbility s : c.getBasicSpells(c.getState(CardStateName.Original))) {
+                for (SpellAbility s : AbilityUtils.getBasicSpellsFromPlayEffect(c, ai, state)) {
+                    if (!(s instanceof Spell)) {
+                        continue;
+                    }
                     Spell spell = (Spell) s;
                     s.setActivatingPlayer(ai, true);
-                    // timing restrictions still apply
-                    if (!s.getRestrictions().checkTimingRestrictions(c, s))
-                        continue;
                     if (params != null && params.containsKey("CMCLimit")) {
                         Integer cmcLimit = (Integer) params.get("CMCLimit");
                         if (spell.getPayCosts().getTotalMana().getCMC() > cmcLimit)
@@ -188,6 +196,11 @@ public class PlayAi extends SpellAbilityAi {
                 return false;
             }
         });
+
+        if (sa.hasParam("CastTransformed")) {
+            options.forEach(c -> c.changeToState(CardStateName.Original));
+        }
+
         final Card best = ComputerUtilCard.getBestAI(tgtCards);
         if (sa.usesTargeting() && !sa.isTargetNumberValid()) {
             sa.getTargets().add(best);