Prevent chests connecting on claim boundary

src/main/java/me/ryanhamshire/GriefPrevention/BlockEventHandler.java

@@ -33,6 +33,7 @@
 import org.bukkit.block.Hopper;
 import org.bukkit.block.PistonMoveReaction;
 import org.bukkit.block.data.BlockData;
+import org.bukkit.block.data.type.Chest;
 import org.bukkit.block.data.type.Dispenser;
 import org.bukkit.entity.Fireball;
 import org.bukkit.entity.Item;
@@ -82,6 +83,13 @@ public class BlockEventHandler implements Listener
 
     private final EnumSet<Material> trashBlocks;
 
+    private static final BlockFace[] HORIZONTAL_DIRECTIONS = new BlockFace[] {
+            BlockFace.NORTH,
+            BlockFace.EAST,
+            BlockFace.SOUTH,
+            BlockFace.WEST
+    };
+
     //constructor
     public BlockEventHandler(DataStore dataStore)
     {
@@ -285,6 +293,38 @@ public void onBlockPlace(BlockPlaceEvent placeEvent)
         //if the block is being placed within or under an existing claim
         PlayerData playerData = this.dataStore.getPlayerData(player.getUniqueId());
         Claim claim = this.dataStore.getClaimAt(block.getLocation(), true, playerData.lastClaim);
+        UUID claimOwner = claim == null ? null : claim.getOwnerID();
+
+        // Check for double chests placed just outside the claim boundary
+        if (block.getBlockData() instanceof Chest)
+        {
+            for (BlockFace face : HORIZONTAL_DIRECTIONS)
+            {
+                Block relative = block.getRelative(face);
+                if (!(relative.getBlockData() instanceof Chest)) continue;
+
+                Claim relativeClaim = this.dataStore.getClaimAt(relative.getLocation(), true, claim);
+                UUID relativeClaimOwner = relativeClaim == null ? null : relativeClaim.getOwnerID();
+
+                // Chests outside claims should connect (both null)
+                // and chests inside the same claim should connect (equal)
+                if (Objects.equals(claimOwner, relativeClaimOwner)) break;
+
+                // Change both chests to singular chests
+                Chest chest = (Chest) block.getBlockData();
+                chest.setType(Chest.Type.SINGLE);
+                block.setBlockData(chest);
+
+                Chest relativeChest = (Chest) relative.getBlockData();
+                relativeChest.setType(Chest.Type.SINGLE);
+                relative.setBlockData(relativeChest);
+
+                // Resend relative chest block to prevent visual bug
+                player.sendBlockChange(relative.getLocation(), relativeChest);
+                break;
+            }
+        }
+
         if (claim != null)
         {
             playerData.lastClaim = claim;