Add basic AI For Discover (#11184)

Author: tehdiplomat

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

@@ -3,8 +3,10 @@
 import forge.ai.*;
 import forge.game.ability.AbilityUtils;
 import forge.game.card.Card;
+import forge.game.cost.Cost;
 import forge.game.player.Player;
 import forge.game.player.PlayerActionConfirmMode;
+import forge.game.spellability.AbilitySub;
 import forge.game.spellability.Spell;
 import forge.game.spellability.SpellAbility;
 
@@ -14,7 +16,32 @@ public class DiscoverAi extends SpellAbilityAi {
 
     @Override
     protected AiAbilityDecision checkApiLogic(final Player ai, final SpellAbility sa) {
-        return new AiAbilityDecision(0, AiPlayDecision.CantPlayAi);
+        if (sa instanceof AbilitySub) {
+            // If its a subability, just let the AI do it. Casting spells is fun!
+            return new AiAbilityDecision(100, AiPlayDecision.WillPlay);
+        }
+
+        Card c = sa.getHostCard();
+        Cost cost = sa.getPayCosts();
+        if (cost != null) {
+            // IF self sacrifice, make sure its "work it". For lands, make sure we still have a decent amount of lands. Or not losing a color source we might need
+            if (ComputerUtilCost.isSacrificeSelfCost(cost)) {
+                if (c.isLand()) {
+                    // The discover lands cost 5 plus tapping this land to activate.
+                    // Let's make sure we don't have too few lands in play before we sacrifice this land.
+                    if (ai.getLandsInPlay().size() <= 6) {
+                        return new AiAbilityDecision(0, AiPlayDecision.CantPlayAi);
+                    }
+                }
+            }
+
+            // Other discover costs that we should probably consider:
+            // Sub Loyalty
+            // Exile creature card from graveyard
+            // Tapping creatures/artifacts
+         }
+
+        return new AiAbilityDecision(100, AiPlayDecision.WillPlay);
     }
 
     /**
@@ -34,6 +61,11 @@ protected AiAbilityDecision doTriggerNoCost(final Player ai, final SpellAbility
             return new AiAbilityDecision(100, AiPlayDecision.WillPlay);
         }
 
+        // If cost is free, and we're just resolving a trigger, lets just do it.
+        if (sa.getPayCosts() == null || sa.getPayCosts().isFree()) {
+            return new AiAbilityDecision(100, AiPlayDecision.WillPlay);
+        }
+
         return checkApiLogic(ai, sa);
     }
 

forge-game/src/main/java/forge/game/cost/Cost.java

@@ -74,6 +74,9 @@ public final boolean hasManaCost() {
         return this.getCostMana() != null;
     }
 
+    public final boolean isFree() {
+        return isOnlyManaCost() && getTotalMana().isZero();
+    }
     public final boolean hasSpecificCostType(Class<? extends CostPart> costType) {
         for (CostPart p : getCostParts()) {
             if (costType.isInstance(p)) {