Add Season of the Witch

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

@@ -682,6 +682,8 @@ public class AiAttackController {
         final boolean bAssault = this.doAssault(ai);
         // TODO: detect Lightmine Field by presence of a card with a specific trigger
         final boolean lightmineField = ComputerUtilCard.isPresentOnBattlefield(ai.getGame(), "Lightmine Field");
+        // TODO: detect Season of the Witch by presence of a card with a specific trigger
+        final boolean seasonOfTheWitch = ComputerUtilCard.isPresentOnBattlefield(ai.getGame(), "Season of the Witch");
 
         // Determine who will be attacked
         GameEntity defender = this.chooseDefender(combat, bAssault);
@@ -715,6 +717,9 @@ public class AiAttackController {
             } else if (attacker.hasSVar("EndOfTurnLeavePlay")
                     && isEffectiveAttacker(ai, attacker, combat)) {
                 mustAttack = true;
+            } else if (seasonOfTheWitch) {
+                // TODO: if there are other ways to tap this creature (like mana creature), then don't need to attack
+                mustAttack = true;
             } else {
                 for (KeywordInterface inst : attacker.getKeywords()) {
                     String s = inst.getOriginal();

forge-game/src/main/java/forge/game/card/CardProperty.java

@@ -17,6 +17,7 @@ import forge.game.ability.AbilityUtils;
 import forge.game.card.CardPredicates.Presets;
 import forge.game.combat.AttackingBand;
 import forge.game.combat.Combat;
+import forge.game.combat.CombatUtil;
 import forge.game.keyword.Keyword;
 import forge.game.mana.Mana;
 import forge.game.player.Player;
@@ -1622,6 +1623,9 @@ public class CardProperty {
             if (band == null || !band.getAttackers().contains(card)) {
                 return false;
             }
+        } else if (property.equals("couldAttackButNotAttacking")) {
+            if (!game.getPhaseHandler().isPlayerTurn(controller)) return false;
+            return CombatUtil.couldAttackButNotAttacking(combat, card);
         } else if (property.startsWith("kicked")) {
             if (property.equals("kicked")) {
                 if (card.getKickerMagnitude() == 0) {

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

@@ -45,6 +45,7 @@ import forge.util.collect.FCollectionView;
 import forge.util.maps.MapToAmount;
 import org.apache.commons.lang3.tuple.Pair;
 
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -82,6 +83,38 @@ public class CombatUtil {
         return myViolations <= bestAttack.getRight().intValue();
     }
 
+    /**
+     * Check if attacker could attack without violating any constraints.
+     */
+    public static boolean couldAttackButNotAttacking(Combat combat, final Card attacker) {
+        // If the player didn't declare attackers, combat here will be null
+        if (combat == null) {
+            combat = new Combat(attacker.getController());
+        } else if (combat.isAttacking(attacker)) {
+            return false;
+        }
+
+        final AttackConstraints constraints = combat.getAttackConstraints();
+        final Pair<Map<Card, GameEntity>, Integer> bestAttack = constraints.getLegalAttackers();
+        final Map<Card, GameEntity> attackers = new HashMap<>(combat.getAttackersAndDefenders());
+        final Game game = attacker.getGame();
+
+        return Iterables.any(getAllPossibleDefenders(attacker.getController()), new Predicate<GameEntity>() {
+            @Override
+            public boolean apply(final GameEntity defender) {
+                if (!canAttack(attacker, defender) || getAttackCost(game, attacker, defender) != null) {
+                    return false;
+                }
+                attackers.put(attacker, defender);
+                final int myViolations = constraints.countViolations(attackers);
+                if (myViolations == -1) {
+                    return false;
+                }
+                return myViolations <= bestAttack.getRight().intValue();
+            }
+        });
+    }
+
     /**
      * <p>
      * Check whether a player should be given the chance to attack this combat.

forge-gui/res/cardsfolder/s/season_of_the_witch.txt

@@ -0,0 +1,13 @@
+Name:Season of the Witch
+ManaCost:B B B
+Types:Enchantment
+K:UpkeepCost:PayLife<2>
+T:Mode$ Phase | Mode$ Phase | Phase$ Declare Attackers | Execute$ TrigMarkCouldAttack | Static$ True
+SVar:TrigMarkCouldAttack:DB$ PumpAll | ValidCards$ Creature.couldAttackButNotAttacking | RememberAllPumped$ True
+T:Mode$ Phase | Phase$ End of Turn | TriggerZones$ Battlefield | Execute$ TrigDestroyAll | TriggerDescription$ At the beginning of the end step, destroy all untapped creatures that didn't attack this turn, except for creatures that couldn't attack.
+SVar:TrigDestroyAll:DB$ DestroyAll | ValidCards$ Creature.untapped+IsRemembered
+T:Mode$ Phase | Phase$ Cleanup | Execute$ TrigCleanup | Static$ True
+SVar:TrigCleanup:DB$ Cleanup | ClearRemembered$ True
+SVar:NonStackingEffect:True
+AI:RemoveDeck:Random
+Oracle:At the beginning of your upkeep, sacrifice Season of the Witch unless you pay 2 life.\nAt the beginning of the end step, destroy all untapped creatures that didn't attack this turn, except for creatures that couldn't attack.