From 0000000000000000000000000000000000000000 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/EntityHuman.java b/src/main/java/net/minecraft/server/EntityHuman.java
index 0cf43351bd2d1ba00217ee9b37a51dbc5a271f7a..9b5683240478acae516481026cb7802dc5757413 100644
--- a/src/main/java/net/minecraft/server/EntityHuman.java
+++ b/src/main/java/net/minecraft/server/EntityHuman.java
@@ -1080,7 +1080,7 @@ public abstract class EntityHuman extends EntityLiving {
                     if (flag5) {
                         if (i > 0) {
                             if (entity instanceof EntityLiving) {
-                                ((EntityLiving) entity).a((float) i * 0.5F, (double) MathHelper.sin(this.yaw * 0.017453292F), (double) (-MathHelper.cos(this.yaw * 0.017453292F)));
+                                ((EntityLiving) entity).doKnockback((float) i * 0.5F, (double) MathHelper.sin(this.yaw * 0.017453292F), (double) (-MathHelper.cos(this.yaw * 0.017453292F)), this); // Paper
                             } else {
                                 entity.i((double) (-MathHelper.sin(this.yaw * 0.017453292F) * (float) i * 0.5F), 0.1D, (double) (MathHelper.cos(this.yaw * 0.017453292F) * (float) i * 0.5F));
                             }
@@ -1104,7 +1104,7 @@ public abstract class EntityHuman extends EntityLiving {
                                 if (entityliving != this && entityliving != entity && !this.r(entityliving) && (!(entityliving instanceof EntityArmorStand) || !((EntityArmorStand) entityliving).isMarker()) && this.h((Entity) entityliving) < 9.0D) {
                                     // CraftBukkit start - Only apply knockback if the damage hits
                                     if (entityliving.damageEntity(DamageSource.playerAttack(this).sweep(), f4)) {
-                                    entityliving.a(0.4F, (double) MathHelper.sin(this.yaw * 0.017453292F), (double) (-MathHelper.cos(this.yaw * 0.017453292F)));
+                                    entityliving.doKnockback(0.4F, (double) MathHelper.sin(this.yaw * 0.017453292F), (double) (-MathHelper.cos(this.yaw * 0.017453292F)), this); // Paper
                                     }
                                     // CraftBukkit end
                                 }
diff --git a/src/main/java/net/minecraft/server/EntityInsentient.java b/src/main/java/net/minecraft/server/EntityInsentient.java
index 6274cf1975270fdac8ae4986e1c170bd075d640e..fbecc8ccab47b428c43530ad344e325538cf242d 100644
--- a/src/main/java/net/minecraft/server/EntityInsentient.java
+++ b/src/main/java/net/minecraft/server/EntityInsentient.java
@@ -1500,7 +1500,7 @@ public abstract class EntityInsentient extends EntityLiving {
 
         if (flag) {
             if (f1 > 0.0F && entity instanceof EntityLiving) {
-                ((EntityLiving) entity).a(f1 * 0.5F, (double) MathHelper.sin(this.yaw * 0.017453292F), (double) (-MathHelper.cos(this.yaw * 0.017453292F)));
+                ((EntityLiving) entity).doKnockback(f1 * 0.5F, (double) MathHelper.sin(this.yaw * 0.017453292F), (double) (-MathHelper.cos(this.yaw * 0.017453292F)), this); // Paper
                 this.setMot(this.getMot().d(0.6D, 1.0D, 0.6D));
             }
 
diff --git a/src/main/java/net/minecraft/server/EntityLiving.java b/src/main/java/net/minecraft/server/EntityLiving.java
index f8c9c4e41faed2a76ca6ff4105351b09c2193cdd..014f27ab7c183e3b416e96d6bbbbfc776e54ca84 100644
--- a/src/main/java/net/minecraft/server/EntityLiving.java
+++ b/src/main/java/net/minecraft/server/EntityLiving.java
@@ -1246,7 +1246,7 @@ public abstract class EntityLiving extends Entity {
                     }
 
                     this.ap = (float) (MathHelper.d(d1, d0) * 57.2957763671875D - (double) this.yaw);
-                    this.a(0.4F, d0, d1);
+                    this.doKnockback(0.4F, d0, d1, entity1); // Paper
                 } else {
                     this.ap = (float) ((int) (Math.random() * 2.0D) * 180);
                 }
@@ -1294,7 +1294,7 @@ public abstract class EntityLiving extends Entity {
     }
 
     protected void e(EntityLiving entityliving) {
-        entityliving.a(0.5F, entityliving.locX() - this.locX(), entityliving.locZ() - this.locZ());
+        entityliving.doKnockback(0.5F, entityliving.locX() - this.locX(), entityliving.locZ() - this.locZ(), this); // Paper
     }
 
     private boolean f(DamageSource damagesource) {
@@ -1537,6 +1537,11 @@ public abstract class EntityLiving extends Entity {
     }
 
     public void a(float f, double d0, double d1) {
+        // Paper start - add knockbacking entity parameter
+        this.doKnockback(f, d0, d1, null);
+    }
+    public void doKnockback(float f, double d0, double d1, Entity knockingBackEntity) {
+        // Paper end - add knockbacking entity parameter
         f = (float) ((double) f * (1.0D - this.b(GenericAttributes.KNOCKBACK_RESISTANCE)));
         if (f > 0.0F) {
             this.impulse = true;
@@ -1544,6 +1549,16 @@ 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 (knockingBackEntity == null || new com.destroystokyo.paper.event.entity.EntityKnockbackByEntityEvent((LivingEntity) getBukkitEntity(), knockingBackEntity.getBukkitEntity(), f, delta).callEvent()) {
+                this.setMot(vec3d.x + delta.getX(), vec3d.y + delta.getY(), vec3d.z + delta.getZ());
+            }
+            // Paper end
         }
     }