From 9ae191c6f59ffb79a82390660f5d5524a0b8f9fe Mon Sep 17 00:00:00 2001
From: Brokkonaut <hannos17@gmx.de>
Date: Mon, 18 Jun 2018 15:46:23 +0200
Subject: [PATCH] Implement EntityKnockbackByEntityEvent

This event is called when an entity receives knockback by another entity.

diff --git a/src/main/java/net/minecraft/server/EntityLiving.java b/src/main/java/net/minecraft/server/EntityLiving.java
index ecbfe8cf8d..66daa77d10 100644
--- a/src/main/java/net/minecraft/server/EntityLiving.java
+++ b/src/main/java/net/minecraft/server/EntityLiving.java
@@ -1424,6 +1424,16 @@ public abstract class EntityLiving extends Entity {
             Vec3D vec3d1 = (new Vec3D(d0, 0.0D, d1)).d().a((double) f);
 
             this.setMot(vec3d.x / 2.0D - vec3d1.x, this.onGround ? Math.min(0.4D, vec3d.y / 2.0D + (double) f) : vec3d.y, vec3d.z / 2.0D - vec3d1.z);
+
+            // Paper start - call EntityKnockbackByEntityEvent
+            Vec3D currentMot = this.getMot();
+            org.bukkit.util.Vector delta = new org.bukkit.util.Vector(currentMot.x - vec3d.x, currentMot.y - vec3d.y, currentMot.z - vec3d.z);
+            // Restore old velocity to be able to access it in the event
+            this.setMot(vec3d);
+            if (entity == null || new com.destroystokyo.paper.event.entity.EntityKnockbackByEntityEvent((LivingEntity) getBukkitEntity(), entity.getBukkitEntity(), f, delta).callEvent()) {
+                this.setMot(vec3d.x + delta.getX(), vec3d.y + delta.getY(), vec3d.z + delta.getZ());
+            }
+            // Paper end
         }
     }
 
-- 
2.21.0