Implemented Arena Trickster

Mage/src/main/java/mage/abilities/common/FirstSpellOpponentsTurnTriggeredAbility.java

@@ -0,0 +1,50 @@
+package mage.abilities.common;
+
+import mage.abilities.effects.Effect;
+import mage.filter.FilterSpell;
+import mage.game.Game;
+import mage.game.events.GameEvent;
+import mage.game.stack.Spell;
+import mage.watchers.common.SpellsCastWatcher;
+
+import java.util.List;
+
+/**
+ * @author TheElk801
+ */
+public class FirstSpellOpponentsTurnTriggeredAbility extends SpellCastControllerTriggeredAbility {
+
+    private static final FilterSpell defaultFilter
+            = new FilterSpell("your first spell during each opponent's turn");
+
+    public FirstSpellOpponentsTurnTriggeredAbility(Effect effect, boolean optional) {
+        super(effect, defaultFilter, optional);
+        this.addWatcher(new SpellsCastWatcher());
+    }
+
+    private FirstSpellOpponentsTurnTriggeredAbility(final FirstSpellOpponentsTurnTriggeredAbility ability) {
+        super(ability);
+    }
+
+    @Override
+    public FirstSpellOpponentsTurnTriggeredAbility copy() {
+        return new FirstSpellOpponentsTurnTriggeredAbility(this);
+    }
+
+    @Override
+    public boolean checkTrigger(GameEvent event, Game game) {
+        if (game.isActivePlayer(this.getControllerId()) // ignore controller turn
+                || !super.checkTrigger(event, game)
+                || !game.getOpponents(this.getControllerId()).contains(game.getActivePlayerId())) {
+            return false;
+        }
+
+        SpellsCastWatcher watcher = game.getState().getWatcher(SpellsCastWatcher.class);
+        if (watcher == null) {
+            return false;
+        }
+
+        List<Spell> spells = watcher.getSpellsCastThisTurn(event.getPlayerId());
+        return spells != null && spells.size() == 1;
+    }
+}