From 5ec3f4655fe30a63827570877875b0f50c42901c Mon Sep 17 00:00:00 2001
From: "Dylan K. Taylor" <dktapps@pmmp.io>
Date: Fri, 28 Jul 2023 12:52:15 +0100
Subject: [PATCH] EntityDamageByEntityEvent: added APIs to get and set vertical
 knockback limits this was requested and PR'd as far back as 2020 (see #3782).
 Since no issue was filed about this, it became forgotten until #5946.
 However, #5946 overcomplicates the solution to the problem, and breaks BC
 without an obvious reason.

---
 src/entity/Living.php                         |  4 +--
 .../entity/EntityDamageByEntityEvent.php      | 28 ++++++++++++++++++-
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/entity/Living.php b/src/entity/Living.php
index 1b5b582da..4d5e10cb3 100644
--- a/src/entity/Living.php
+++ b/src/entity/Living.php
@@ -557,14 +557,14 @@ abstract class Living extends Entity{
 			$e = $source->getChild();
 			if($e !== null){
 				$motion = $e->getMotion();
-				$this->knockBack($motion->x, $motion->z, $source->getKnockBack());
+				$this->knockBack($motion->x, $motion->z, $source->getKnockBack(), $source->getVerticalKnockBackLimit());
 			}
 		}elseif($source instanceof EntityDamageByEntityEvent){
 			$e = $source->getDamager();
 			if($e !== null){
 				$deltaX = $this->location->x - $e->location->x;
 				$deltaZ = $this->location->z - $e->location->z;
-				$this->knockBack($deltaX, $deltaZ, $source->getKnockBack());
+				$this->knockBack($deltaX, $deltaZ, $source->getKnockBack(), $source->getVerticalKnockBackLimit());
 			}
 		}
 
diff --git a/src/event/entity/EntityDamageByEntityEvent.php b/src/event/entity/EntityDamageByEntityEvent.php
index b8eb95def..5ef6c4b8e 100644
--- a/src/event/entity/EntityDamageByEntityEvent.php
+++ b/src/event/entity/EntityDamageByEntityEvent.php
@@ -36,7 +36,15 @@ class EntityDamageByEntityEvent extends EntityDamageEvent{
 	/**
 	 * @param float[] $modifiers
 	 */
-	public function __construct(Entity $damager, Entity $entity, int $cause, float $damage, array $modifiers = [], private float $knockBack = Living::DEFAULT_KNOCKBACK_FORCE){
+	public function __construct(
+		Entity $damager,
+		Entity $entity,
+		int $cause,
+		float $damage,
+		array $modifiers = [],
+		private float $knockBack = Living::DEFAULT_KNOCKBACK_FORCE,
+		private float $verticalKnockBackLimit = Living::DEFAULT_KNOCKBACK_VERTICAL_LIMIT
+	){
 		$this->damagerEntityId = $damager->getId();
 		parent::__construct($entity, $cause, $damage, $modifiers);
 		$this->addAttackerModifiers($damager);
@@ -79,4 +87,22 @@ class EntityDamageByEntityEvent extends EntityDamageEvent{
 	public function setKnockBack(float $knockBack) : void{
 		$this->knockBack = $knockBack;
 	}
+
+	/**
+	 * Returns the maximum upwards velocity the victim may have after being knocked back.
+	 * This ensures that the victim doesn't fly up into the sky when high levels of knockback are applied.
+	 *
+	 * @see Living::DEFAULT_KNOCKBACK_VERTICAL_LIMIT
+	 */
+	public function getVerticalKnockBackLimit() : float{
+		return $this->verticalKnockBackLimit;
+	}
+
+	/**
+	 * Sets the maximum upwards velocity the victim may have after being knocked back.
+	 * Larger values will allow the victim to fly higher if the knockback force is also large.
+	 */
+	public function setVerticalKnockBackLimit(float $verticalKnockBackLimit) : void{
+		$this->verticalKnockBackLimit = $verticalKnockBackLimit;
+	}
 }