new common class for life drain effects

"Each opponent loses X life. You gain life equal to the life lost this way."

Mage/src/main/java/mage/abilities/effects/common/LoseLifeOpponentsYouGainLifeLostEffect.java

@@ -0,0 +1,63 @@
+package mage.abilities.effects.common;
+
+import mage.abilities.Ability;
+import mage.abilities.dynamicvalue.DynamicValue;
+import mage.abilities.dynamicvalue.common.StaticValue;
+import mage.abilities.effects.OneShotEffect;
+import mage.constants.Outcome;
+import mage.game.Game;
+import mage.players.Player;
+
+import java.util.Objects;
+
+/**
+ * @author xenohedron
+ */
+public class LoseLifeOpponentsYouGainLifeLostEffect extends OneShotEffect {
+
+    private final DynamicValue amount;
+
+    public LoseLifeOpponentsYouGainLifeLostEffect(int amount) {
+        this(StaticValue.get(amount), amount + " life");
+    }
+
+    public LoseLifeOpponentsYouGainLifeLostEffect(DynamicValue amount, String amountLifeText) {
+        super(Outcome.GainLife);
+        this.amount = amount;
+        staticText = "each opponent loses " + amountLifeText + ". You gain life equal to the life lost this way";
+    }
+
+    protected LoseLifeOpponentsYouGainLifeLostEffect(final LoseLifeOpponentsYouGainLifeLostEffect effect) {
+        super(effect);
+        this.amount = effect.amount;
+    }
+
+    @Override
+    public boolean apply(Game game, Ability source) {
+        Player controller = game.getPlayer(source.getControllerId());
+        if (controller == null) {
+            return false;
+        }
+        int lifeToLose = amount.calculate(game, source, this);
+        if (lifeToLose < 1) {
+            return true;
+        }
+        int totalLifeLost = game
+                .getOpponents(source.getControllerId())
+                .stream()
+                .map(game::getPlayer)
+                .filter(Objects::nonNull)
+                .mapToInt(opponent -> opponent.loseLife(lifeToLose, game, source, false))
+                .sum();
+        if (totalLifeLost > 1) {
+            controller.gainLife(totalLifeLost, game, source);
+        }
+        return true;
+    }
+
+    @Override
+    public LoseLifeOpponentsYouGainLifeLostEffect copy() {
+        return new LoseLifeOpponentsYouGainLifeLostEffect(this);
+    }
+
+}