implement [MH3] Hydra Trainer

Mage.Sets/src/mage/cards/h/HydraTrainer.java

@@ -0,0 +1,94 @@
+package mage.cards.h;
+
+import mage.MageInt;
+import mage.abilities.Ability;
+import mage.abilities.common.BecomesExertSourceTriggeredAbility;
+import mage.abilities.dynamicvalue.DynamicValue;
+import mage.abilities.effects.Effect;
+import mage.abilities.effects.common.continuous.BoostTargetEffect;
+import mage.abilities.hint.Hint;
+import mage.abilities.hint.ValueHint;
+import mage.abilities.keyword.AdaptAbility;
+import mage.abilities.keyword.ExertAbility;
+import mage.cards.CardImpl;
+import mage.cards.CardSetInfo;
+import mage.constants.CardType;
+import mage.constants.SubType;
+import mage.counters.Counter;
+import mage.game.Game;
+import mage.target.common.TargetCreaturePermanent;
+
+import java.util.Objects;
+import java.util.UUID;
+
+/**
+ * @author Susucr
+ */
+public final class HydraTrainer extends CardImpl {
+
+    public HydraTrainer(UUID ownerId, CardSetInfo setInfo) {
+        super(ownerId, setInfo, new CardType[]{CardType.CREATURE}, "{1}{G}");
+
+        this.subtype.add(SubType.HUMAN);
+        this.subtype.add(SubType.WARRIOR);
+        this.power = new MageInt(1);
+        this.toughness = new MageInt(1);
+
+        // You may exert Hydra Trainer as it attacks. When you do, target creature gets +X/+X until end of turn, where X is the number of counters on permanents you control.
+        BecomesExertSourceTriggeredAbility trigger = new BecomesExertSourceTriggeredAbility(
+                new BoostTargetEffect(HydraTrainerValue.instance, HydraTrainerValue.instance)
+                        .setText("target creature gets +X/+X until end of turn, where X is the number of counters on permanents you control")
+        );
+        trigger.addTarget(new TargetCreaturePermanent());
+        this.addAbility(new ExertAbility(trigger).addHint(HydraTrainerValue.getHint()));
+
+        // {2}{G}: Adapt 2.
+        this.addAbility(new AdaptAbility(2, "{2}{G}"));
+    }
+
+    private HydraTrainer(final HydraTrainer card) {
+        super(card);
+    }
+
+    @Override
+    public HydraTrainer copy() {
+        return new HydraTrainer(this);
+    }
+}
+
+enum HydraTrainerValue implements DynamicValue {
+    instance;
+
+    private static final Hint hint = new ValueHint("Number of counters on permanents you control", instance);
+
+    public static Hint getHint() {
+        return hint;
+    }
+
+    @Override
+    public int calculate(Game game, Ability sourceAbility, Effect effect) {
+        return game.getBattlefield()
+                .getAllActivePermanents(sourceAbility.getControllerId())
+                .stream()
+                .filter(Objects::nonNull)
+                .map(perm -> perm.getCounters(game))
+                .flatMap(counters -> counters.values().stream())
+                .mapToInt(Counter::getCount)
+                .sum();
+    }
+
+    @Override
+    public HydraTrainerValue copy() {
+        return this;
+    }
+
+    @Override
+    public String toString() {
+        return "X";
+    }
+
+    @Override
+    public String getMessage() {
+        return "the number of counters on permanents you control";
+    }
+}

Mage.Sets/src/mage/sets/ModernHorizons3.java

@@ -95,6 +95,7 @@ public final class ModernHorizons3 extends ExpansionSet {
         cards.add(new SetCardInfo("Harbinger of the Seas", 63, Rarity.RARE, mage.cards.h.HarbingerOfTheSeas.class));
         cards.add(new SetCardInfo("Hexgold Slith", 30, Rarity.COMMON, mage.cards.h.HexgoldSlith.class));
         cards.add(new SetCardInfo("Horrid Shadowspinner", 188, Rarity.UNCOMMON, mage.cards.h.HorridShadowspinner.class));
+        cards.add(new SetCardInfo("Hydra Trainer", 159, Rarity.UNCOMMON, mage.cards.h.HydraTrainer.class));
         cards.add(new SetCardInfo("Idol of False Gods", 210, Rarity.UNCOMMON, mage.cards.i.IdolOfFalseGods.class));
         cards.add(new SetCardInfo("Island", 305, Rarity.LAND, mage.cards.basiclands.Island.class, FULL_ART_BFZ_VARIOUS));
         cards.add(new SetCardInfo("It That Heralds the End", 9, Rarity.UNCOMMON, mage.cards.i.ItThatHeraldsTheEnd.class));