From fe490032d60724fdcdfbb8215c11acb47e8f58bc Mon Sep 17 00:00:00 2001
From: Joshua Castle <26531652+Kas-tle@users.noreply.github.com>
Date: Sat, 13 May 2023 14:16:24 -0700
Subject: [PATCH] Properly handle if extended collision box is below

Signed-off-by: Joshua Castle <26531652+Kas-tle@users.noreply.github.com>
---
 .../org/geysermc/geyser/util/ChunkUtils.java    | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/core/src/main/java/org/geysermc/geyser/util/ChunkUtils.java b/core/src/main/java/org/geysermc/geyser/util/ChunkUtils.java
index f21ffed40..16298cdbf 100644
--- a/core/src/main/java/org/geysermc/geyser/util/ChunkUtils.java
+++ b/core/src/main/java/org/geysermc/geyser/util/ChunkUtils.java
@@ -113,6 +113,19 @@ public class ChunkUtils {
     public static void updateBlock(GeyserSession session, int blockState, Vector3i position) {
         updateBlockClientSide(session, blockState, position);
         session.getChunkCache().updateBlock(position.getX(), position.getY(), position.getZ(), blockState);
+
+        if (!session.getBlockMappings().getExtendedCollisionBoxes().isEmpty()) {
+            int belowBlock = session.getGeyser().getWorldManager().getBlockAt(session, position.getX(), position.getY() - 1, position.getZ());
+            BlockDefinition belowBedrockExtendedCollisionDefinition = session.getBlockMappings().getExtendedCollisionBoxes().get(belowBlock);
+            if (belowBedrockExtendedCollisionDefinition != null && blockState == BlockStateValues.JAVA_AIR_ID) {
+                UpdateBlockPacket updateBlockPacket = new UpdateBlockPacket();
+                updateBlockPacket.setDataLayer(0);
+                updateBlockPacket.setBlockPosition(position);
+                updateBlockPacket.setDefinition(belowBedrockExtendedCollisionDefinition);
+                updateBlockPacket.getFlags().add(UpdateBlockPacket.Flag.NETWORK);
+                session.sendUpstreamPacket(updateBlockPacket);
+            }
+        }
     }
 
     /**
@@ -146,9 +159,9 @@ public class ChunkUtils {
 
         // Extended collision boxes for custom blocks
         if (!session.getBlockMappings().getExtendedCollisionBoxes().isEmpty()) {
-            BlockDefinition aboveBedrockExtendedCollisionDefinition = session.getBlockMappings().getExtendedCollisionBoxes().get(blockState);
             int aboveBlock = session.getGeyser().getWorldManager().getBlockAt(session, position.getX(), position.getY() + 1, position.getZ());
-            if (aboveBedrockExtendedCollisionDefinition != null) {
+            BlockDefinition aboveBedrockExtendedCollisionDefinition = session.getBlockMappings().getExtendedCollisionBoxes().get(blockState);
+            if (aboveBedrockExtendedCollisionDefinition != null && aboveBlock == BlockStateValues.JAVA_AIR_ID) {
                 UpdateBlockPacket updateBlockPacket = new UpdateBlockPacket();
                 updateBlockPacket.setDataLayer(0);
                 updateBlockPacket.setBlockPosition(position.add(0, 1, 0));