From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: William Blake Galbreath <blake.galbreath@gmail.com>
Date: Sat, 6 Jul 2019 17:00:04 -0500
Subject: [PATCH] Dont send useless entity packets

Original code by PurpurMC, licensed under MIT
You can find the original code on https://github.com/PurpurMC/Purpur

diff --git a/src/main/java/dev/etil/mirai/MiraiConfig.java b/src/main/java/dev/etil/mirai/MiraiConfig.java
index 8717e40515dbc7cfbb5b45ce706f5c720596b5fc..d867baee944627e1a1419611fac2d3385350b182 100644
--- a/src/main/java/dev/etil/mirai/MiraiConfig.java
+++ b/src/main/java/dev/etil/mirai/MiraiConfig.java
@@ -152,4 +152,10 @@ public class MiraiConfig {
         checkVehicleFlying = getBoolean("checks.vehicle-flight", true,
             "Whether or not vanilla anticheat should check for passengers flying.");
     }
+
+    public static boolean dontSendUselessEntityPackets;
+    private static void uselessEntityPackets() {
+        dontSendUselessEntityPackets = getBoolean("dont-send-useless-entity-packets", true,
+            "Whether or not server should send entity packets with null movements.");
+    }
 }
diff --git a/src/main/java/net/minecraft/server/level/ServerEntity.java b/src/main/java/net/minecraft/server/level/ServerEntity.java
index da459fa2bd8ad4b05a0ae99552db2709a5169c2a..b99eeae741c1042ae5d925957a87481c113f9502 100644
--- a/src/main/java/net/minecraft/server/level/ServerEntity.java
+++ b/src/main/java/net/minecraft/server/level/ServerEntity.java
@@ -206,6 +206,7 @@ public class ServerEntity {
                         flag4 = true;
                         flag5 = true;
                     }
+                    if (dev.etil.mirai.MiraiConfig.dontSendUselessEntityPackets && isUselessPacket(packet1)) packet1 = null; // Purpur
                 }
 
                 if ((this.trackDelta || this.entity.hasImpulse || this.entity instanceof LivingEntity && ((LivingEntity) this.entity).isFallFlying()) && this.tickCount > 0) {
@@ -278,6 +279,21 @@ public class ServerEntity {
         });
     }
 
+    // Purpur start
+    private boolean isUselessPacket(Packet<?> possibleUselessPacket) {
+        if (possibleUselessPacket instanceof ClientboundMoveEntityPacket packet) {
+            if (possibleUselessPacket instanceof ClientboundMoveEntityPacket.Pos) {
+                return packet.getXa() == 0 && packet.getYa() == 0 && packet.getZa() == 0;
+            } else if (possibleUselessPacket instanceof ClientboundMoveEntityPacket.PosRot) {
+                return packet.getXa() == 0 && packet.getYa() == 0 && packet.getZa() == 0 && packet.getyRot() == 0 && packet.getxRot() == 0;
+            } else if (possibleUselessPacket instanceof ClientboundMoveEntityPacket.Rot) {
+                return packet.getyRot() == 0 && packet.getxRot() == 0;
+            }
+        }
+        return false;
+    }
+    // Purpur end
+
     public void removePairing(ServerPlayer player) {
         this.entity.stopSeenByPlayer(player);
         player.connection.send(new ClientboundRemoveEntitiesPacket(new int[]{this.entity.getId()}));