Add history to view previous root steps during the calculation

Author: Yeregorix

src/main/java/org/spongepowered/api/event/cause/entity/damage/DamageStep.java

@@ -95,6 +95,13 @@ default void skip() {
      */
     OptionalDouble damageAfterChildren();
 
+    /**
+     * Gets the {@link DamageStepHistory} this step belongs to.
+     *
+     * @return The history containing this step.
+     */
+    DamageStepHistory history();
+
     /**
      * Gets the parent of this step.
      * Returns empty if this step is the root of its tree.

src/main/java/org/spongepowered/api/event/cause/entity/damage/DamageStepHistory.java

@@ -0,0 +1,43 @@
+/*
+ * This file is part of SpongeAPI, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) SpongePowered <https://www.spongepowered.org>
+ * Copyright (c) contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package org.spongepowered.api.event.cause.entity.damage;
+
+import java.util.List;
+
+/**
+ * Captures the root steps occurring during a damage calculation.
+ */
+public interface DamageStepHistory {
+
+    /**
+     * Gets the list of the captured root steps during the damage calculation in the order they have been applied.
+     * Note that this list is not an exhaustive representation of all the operations applied,
+     * especially in a modded environment.
+     * The list is unmodifiable and will gradually grow during the damage calculation.
+     *
+     * @return The root steps.
+     */
+    List<DamageStep> rootSteps();
+}

src/main/java/org/spongepowered/api/event/entity/DamageCalculationEvent.java

@@ -30,6 +30,7 @@
 import org.spongepowered.api.event.Event;
 import org.spongepowered.api.event.cause.entity.damage.DamageModifier;
 import org.spongepowered.api.event.cause.entity.damage.DamageStep;
+import org.spongepowered.api.event.cause.entity.damage.DamageStepHistory;
 import org.spongepowered.api.event.cause.entity.damage.DamageStepType;
 import org.spongepowered.api.event.cause.entity.damage.DamageStepTypes;
 import org.spongepowered.api.event.impl.entity.AbstractDamageCalculationEventPre;
@@ -138,12 +139,10 @@ interface Post extends DamageCalculationEvent {
         double finalDamage();
 
         /**
-         * Gets the list of the captured root steps during the damage calculation in the order they have been applied.
-         * Note that this list is not an exhaustive representation of all the operations applied,
-         * especially in a modded environment.
+         * Gets the {@link DamageStepHistory} of this damage calculation.
          *
-         * @return The list of root steps
+         * @return The history.
          */
-        List<DamageStep> steps();
+        DamageStepHistory history();
     }
 }