refactor SavedGainedLifeValue instead of getValue("gainedLife")

Mage/src/main/java/mage/abilities/dynamicvalue/common/SavedGainedLifeValue.java

@@ -0,0 +1,45 @@
+package mage.abilities.dynamicvalue.common;
+
+import mage.abilities.Ability;
+import mage.abilities.dynamicvalue.DynamicValue;
+import mage.abilities.effects.Effect;
+import mage.game.Game;
+
+import java.util.Optional;
+
+/**
+ * Stores gained life value in relevant triggers, to pass down on effects.
+ *
+ * @author Susucr
+ */
+public enum SavedGainedLifeValue implements DynamicValue {
+    MANY("many"),
+    MUCH("much");
+
+    private final String message;
+    public static final String VALUE_KEY = "gainedLife";
+
+    SavedGainedLifeValue(String message) {
+        this.message = "that " + message;
+    }
+
+    @Override
+    public int calculate(Game game, Ability sourceAbility, Effect effect) {
+        return Optional.ofNullable((Integer) effect.getValue(VALUE_KEY)).orElse(0);
+    }
+
+    @Override
+    public SavedGainedLifeValue copy() {
+        return this;
+    }
+
+    @Override
+    public String toString() {
+        return message;
+    }
+
+    @Override
+    public String getMessage() {
+        return "";
+    }
+}