Add item-cache as a less expensive way of getting items. (Will rewrite eventually to not depend on Bukkit)

src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/Protocol1_9TO1_8.java

@@ -10,6 +10,7 @@ import us.myles.ViaVersion.ViaVersionPlugin;
 import us.myles.ViaVersion.api.PacketWrapper;
 import us.myles.ViaVersion.api.ViaVersion;
 import us.myles.ViaVersion.api.data.UserConnection;
+import us.myles.ViaVersion.api.minecraft.item.Item;
 import us.myles.ViaVersion.api.minecraft.metadata.Metadata;
 import us.myles.ViaVersion.api.protocol.Protocol;
 import us.myles.ViaVersion.api.remapper.ValueTransformer;
@@ -62,23 +63,27 @@ public class Protocol1_9TO1_8 extends Protocol {
         return line;
     }
 
-    public static ItemStack getHandItem(final UserConnection info) {
-        try {
-            return Bukkit.getScheduler().callSyncMethod(Bukkit.getPluginManager().getPlugin("ViaVersion"), new Callable<ItemStack>() {
-                @Override
-                public ItemStack call() throws Exception {
-                    UUID playerUUID = info.get(ProtocolInfo.class).getUuid();
-                    if (Bukkit.getPlayer(playerUUID) != null) {
-                        return Bukkit.getPlayer(playerUUID).getItemInHand();
+    public static Item getHandItem(final UserConnection info) {
+        if(HandItemCache.CACHE){
+            return HandItemCache.getHandItem(info.get(ProtocolInfo.class).getUuid());
+        }else {
+            try {
+                return Bukkit.getScheduler().callSyncMethod(Bukkit.getPluginManager().getPlugin("ViaVersion"), new Callable<Item>() {
+                    @Override
+                    public Item call() throws Exception {
+                        UUID playerUUID = info.get(ProtocolInfo.class).getUuid();
+                        if (Bukkit.getPlayer(playerUUID) != null) {
+                            return Item.getItem(Bukkit.getPlayer(playerUUID).getItemInHand());
+                        }
+                        return null;
                     }
-                    return null;
-                }
-            }).get(10, TimeUnit.SECONDS);
-        } catch (Exception e) {
-            System.out.println("Error fetching hand item: " + e.getClass().getName());
-            if (ViaVersion.getInstance().isDebug())
-                e.printStackTrace();
-            return null;
+                }).get(10, TimeUnit.SECONDS);
+            } catch (Exception e) {
+                System.out.println("Error fetching hand item: " + e.getClass().getName());
+                if (ViaVersion.getInstance().isDebug())
+                    e.printStackTrace();
+                return null;
+            }
         }
     }
 
@@ -104,6 +109,10 @@ public class Protocol1_9TO1_8 extends Protocol {
         }
         if (plugin.getConfig().getBoolean("simulate-pt", true))
             new ViaIdleThread(plugin.getPortedPlayers()).runTaskTimerAsynchronously(plugin, 1L, 1L); // Updates player's idle status
+        if (plugin.getConfig().getBoolean("item-cache", true)) {
+            new HandItemCache().runTaskTimerAsynchronously(plugin, 2L, 2L); // Updates player's items :)
+            HandItemCache.CACHE = true;
+        }
     }
 
     @Override

src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/listeners/HandItemCache.java

@@ -0,0 +1,36 @@
+package us.myles.ViaVersion.protocols.protocol1_9to1_8.listeners;
+
+import org.bukkit.Bukkit;
+import org.bukkit.entity.Player;
+import org.bukkit.scheduler.BukkitRunnable;
+import us.myles.ViaVersion.api.minecraft.item.Item;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class HandItemCache extends BukkitRunnable {
+    public static boolean CACHE = false;
+    private static ConcurrentHashMap<UUID, Item> handCache = new ConcurrentHashMap<>();
+
+    public static Item getHandItem(UUID player) {
+        if (!handCache.containsKey(player))
+            return null;
+        return handCache.get(player);
+    }
+
+    @Override
+    public void run() {
+        List<UUID> players = new ArrayList<>(handCache.keySet());
+
+        for (Player p : Bukkit.getOnlinePlayers()) {
+            handCache.put(p.getUniqueId(), Item.getItem(p.getItemInHand()));
+            players.remove(p.getUniqueId());
+        }
+        // Remove offline players
+        for (UUID uuid : players) {
+            handCache.remove(uuid);
+        }
+    }
+}

src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/packets/WorldPackets.java

@@ -288,7 +288,7 @@ public class WorldPackets {
                         wrapper.write(Type.LONG, -1L);
                         wrapper.write(Type.BYTE, (byte) 255);
                         // Write item in hand
-                        Item item = Item.getItem(Protocol1_9TO1_8.getHandItem(wrapper.user()));
+                        Item item = Protocol1_9TO1_8.getHandItem(wrapper.user());
                         // Blocking patch
                         if (ViaVersion.getConfig().isShieldBlocking()) {
                             if (item != null) {
@@ -368,7 +368,7 @@ public class WorldPackets {
                 create(new ValueCreator() {
                     @Override
                     public void write(PacketWrapper wrapper) throws Exception {
-                        Item item = Item.getItem(Protocol1_9TO1_8.getHandItem(wrapper.user()));
+                        Item item = Protocol1_9TO1_8.getHandItem(wrapper.user());
                         wrapper.write(Type.ITEM, item); // 3 - Item
                     }
                 });

src/main/resources/config.yml

@@ -29,3 +29,5 @@ use-new-deathmessages: false
 suppress-entityid-errors: false
 # Our patch for block breaking issue, if you have issues with block updates then disable this.
 block-break-patch: true
+# Should we cache our items, this will prevent server from being lagged out, however the cost is a constant task caching items
+item-cache: true