From 00df4c26ba13fc8ddf0c92500b414061b592dae4 Mon Sep 17 00:00:00 2001
From: Camotoy <20743703+Camotoy@users.noreply.github.com>
Date: Tue, 3 Jan 2023 15:51:58 -0500
Subject: [PATCH] Don't send more than one ServerboundSwingPacket per tick

Should address #2875
---
 .../geyser/session/GeyserSession.java         |  1 -
 .../bedrock/BedrockAnimateTranslator.java     | 21 ++++++++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/core/src/main/java/org/geysermc/geyser/session/GeyserSession.java b/core/src/main/java/org/geysermc/geyser/session/GeyserSession.java
index 72697a85c..a95706307 100644
--- a/core/src/main/java/org/geysermc/geyser/session/GeyserSession.java
+++ b/core/src/main/java/org/geysermc/geyser/session/GeyserSession.java
@@ -457,7 +457,6 @@ public class GeyserSession implements GeyserConnection, GeyserCommandSource {
      * Counts how many ticks have occurred since an arm animation started.
      * -1 means there is no active arm swing.
      */
-    @Getter(AccessLevel.NONE)
     private int armAnimationTicks = -1;
 
     /**
diff --git a/core/src/main/java/org/geysermc/geyser/translator/protocol/bedrock/BedrockAnimateTranslator.java b/core/src/main/java/org/geysermc/geyser/translator/protocol/bedrock/BedrockAnimateTranslator.java
index 670e55785..4905b5647 100644
--- a/core/src/main/java/org/geysermc/geyser/translator/protocol/bedrock/BedrockAnimateTranslator.java
+++ b/core/src/main/java/org/geysermc/geyser/translator/protocol/bedrock/BedrockAnimateTranslator.java
@@ -49,11 +49,26 @@ public class BedrockAnimateTranslator extends PacketTranslator<AnimatePacket> {
             case SWING_ARM ->
                 // Delay so entity damage can be processed first
                 session.scheduleInEventLoop(() -> {
+                        if (session.getArmAnimationTicks() != 0) {
+                            // So, generally, a Java player can only do one *thing* at a time.
+                            // If a player right-clicks, for example, then there's probably only one action associated with
+                            // that right-click that will send a swing.
+                            // The only exception I can think of to this, *maybe*, is a player dropping items
+                            // Bedrock is a little funkier than this - it can send several arm animation packets in the
+                            // same tick, notably with high levels of haste applied.
+                            // Packet limiters do not like this and can crash the player.
+                            // If arm animation ticks is 0, then we just sent an arm swing packet this tick.
+                            // See https://github.com/GeyserMC/Geyser/issues/2875
+                            // This behavior was last touched on with ViaVersion 4.5.1 (with its packet limiter), Java 1.16.5,
+                            // and Bedrock 1.19.51.
+                            // Note for the future: we should probably largely ignore this packet and instead replicate
+                            // all actions on our end, and send swings where needed.
                             session.sendDownstreamPacket(new ServerboundSwingPacket(Hand.MAIN_HAND));
                             session.activateArmAnimationTicking();
-                        },
-                        25,
-                        TimeUnit.MILLISECONDS
+                        }
+                    },
+                    25,
+                    TimeUnit.MILLISECONDS
                 );
             // These two might need to be flipped, but my recommendation is getting moving working first
             case ROW_LEFT -> {