Support item stacking, cleanup

src/main/java/net/minestom/server/item/ItemMeta.java

@@ -84,13 +84,27 @@ public class ItemMeta implements Cloneable {
         return customModelData;
     }
 
-    public NBTCompound toNBT() {
+    public @NotNull NBTCompound toNBT() {
         if (cache == null) {
             this.cache = NBTUtils.metaToNBT(this);
         }
         return cache;
     }
 
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        ItemMeta itemMeta = (ItemMeta) o;
+        return toNBT().equals(itemMeta.toNBT());
+    }
+
+    @Override
+    public int hashCode() {
+        return toNBT().hashCode();
+    }
+
     protected @NotNull ItemMetaBuilder builder() {
         return builder.clone();
     }

src/main/java/net/minestom/server/item/ItemStack.java

@@ -14,7 +14,7 @@ import java.util.function.UnaryOperator;
 
 public class ItemStack {
 
-    public static final ItemStack AIR = ItemStack.builder(Material.AIR).build();
+    public static final ItemStack AIR = ItemStack.of(Material.AIR);
 
     private final UUID uuid = UUID.randomUUID();
     private final StackingRule stackingRule = new VanillaStackingRule(64);
@@ -34,7 +34,7 @@ public class ItemStack {
         return new ItemBuilder(material);
     }
 
-    @Contract(value = "_ -> new", pure = true)
+    @Contract(value = "_ ,_ -> new", pure = true)
     public static @NotNull ItemStack of(@NotNull Material material, int amount) {
         return builder(material).amount(amount).build();
     }

src/main/java/net/minestom/server/network/packet/server/play/ChunkDataPacket.java

@@ -24,7 +24,6 @@ import net.minestom.server.utils.chunk.ChunkUtils;
 import net.minestom.server.world.biomes.Biome;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.jglrxavpok.hephaistos.nbt.NBT;
 import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 import org.jglrxavpok.hephaistos.nbt.NBTException;
 

src/main/java/net/minestom/server/utils/NBTUtils.java

@@ -6,15 +6,11 @@ import net.kyori.adventure.text.serializer.gson.GsonComponentSerializer;
 import net.kyori.adventure.util.Codec;
 import net.minestom.server.MinecraftServer;
 import net.minestom.server.adventure.AdventureSerializer;
-import net.minestom.server.attribute.Attribute;
-import net.minestom.server.attribute.AttributeOperation;
-import net.minestom.server.data.Data;
 import net.minestom.server.inventory.Inventory;
 import net.minestom.server.item.Enchantment;
 import net.minestom.server.item.ItemMeta;
 import net.minestom.server.item.ItemStack;
 import net.minestom.server.item.Material;
-import net.minestom.server.item.attribute.AttributeSlot;
 import net.minestom.server.item.attribute.ItemAttribute;
 import net.minestom.server.registry.Registries;
 import net.minestom.server.utils.binary.BinaryReader;
@@ -28,8 +24,6 @@ import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
 import java.io.StringReader;
-import java.util.ArrayList;
-import java.util.List;
 import java.util.Map;
 import java.util.UUID;
 
@@ -286,7 +280,7 @@ public final class NBTUtils {
         }
     }
 
-    public static NBTCompound metaToNBT(@NotNull ItemMeta itemMeta) {
+    public static @NotNull NBTCompound metaToNBT(@NotNull ItemMeta itemMeta) {
         final NBTCompound itemNBT = new NBTCompound();
 
         // Unbreakable
@@ -302,7 +296,7 @@ public final class NBTUtils {
             }
         }
 
-        // Display
+        // Start display
         {
             final var displayName = itemMeta.getDisplayName();
             final var lore = itemMeta.getLore();
@@ -326,14 +320,16 @@ public final class NBTUtils {
                 itemNBT.set("display", displayNBT);
             }
         }
+        // End display
 
-        // Enchantment
+        // Start enchantment
         {
             final var enchantmentMap = itemMeta.getEnchantmentMap();
             if (!enchantmentMap.isEmpty()) {
                 NBTUtils.writeEnchant(itemNBT, "Enchantments", enchantmentMap);
             }
         }
+        // End enchantment
 
         // Start attribute
         {
@@ -358,14 +354,14 @@ public final class NBTUtils {
         }
         // End attribute
 
-        // Start hide flags
+        // Start hide flag
         {
             final int hideFlag = itemMeta.getHideFlag();
             if (hideFlag != 0) {
                 itemNBT.setInt("HideFlags", hideFlag);
             }
         }
-        // End hide flags
+        // End hide flag
 
         // Start custom model data
         {