Add ItemTag

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

@@ -1,9 +1,9 @@
 package net.minestom.server.item;
 
 /**
- * Represents a flag which can be applied to an {@link ItemStack} using {@link ItemStack#addItemFlags(ItemFlag...)}.
+ * Represents a hide flag which can be applied to an {@link ItemStack} using {@link ItemMetaBuilder#hideFlag(int)}.
  */
-public enum ItemFlag {
+public enum ItemHideFlag {
     HIDE_ENCHANTS(1),
     HIDE_ATTRIBUTES(2),
     HIDE_UNBREAKABLE(4),
@@ -13,7 +13,7 @@ public enum ItemFlag {
 
     private final int bitFieldPart;
 
-    ItemFlag(int bit) {
+    ItemHideFlag(int bit) {
         this.bitFieldPart = bit;
     }
 

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

@@ -95,6 +95,15 @@ public class ItemMeta {
         return customModelData;
     }
 
+    @Contract("_, null -> null; _, !null -> !null")
+    public <T> T getOrDefault(@NotNull ItemTag<T> tag, @Nullable T defaultValue) {
+        return tag.read(toNBT());
+    }
+
+    public <T> @Nullable T get(@NotNull ItemTag<T> tag) {
+        return tag.read(toNBT());
+    }
+
     public @NotNull NBTCompound toNBT() {
         if (originalNbt != null) {
             // Return the nbt this meta has been created with
@@ -127,6 +136,6 @@ public class ItemMeta {
 
     @Contract(value = "-> new", pure = true)
     protected @NotNull ItemMetaBuilder builder() {
-        return builder.clone();
+        return ItemMetaBuilder.fromNBT(builder, toNBT());
     }
 }

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

@@ -90,6 +90,22 @@ public abstract class ItemMetaBuilder implements Cloneable {
         return this;
     }
 
+    public <T> @NotNull ItemMetaBuilder set(@NotNull ItemTag<T> tag, @Nullable T value) {
+        if (originalNBT != null) {
+            // Item is from nbt
+            if (value != null) {
+                tag.write(originalNBT, value);
+            } else {
+                this.originalNBT.removeTag(tag.getKey());
+            }
+            return this;
+        } else {
+            // Create item meta based on nbt
+            var currentNbt = build().toNBT();
+            return fromNBT(this, currentNbt).set(tag, value);
+        }
+    }
+
     @Contract("-> new")
     public abstract @NotNull ItemMeta build();
 

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

@@ -0,0 +1,36 @@
+package net.minestom.server.item;
+
+import org.jetbrains.annotations.NotNull;
+import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+
+public abstract class ItemTag<T> {
+
+    private final String key;
+
+    private ItemTag(@NotNull String key) {
+        this.key = key;
+    }
+
+    public @NotNull String getKey() {
+        return key;
+    }
+
+    protected abstract T read(@NotNull NBTCompound nbtCompound);
+
+    protected abstract void write(@NotNull NBTCompound nbtCompound, @NotNull T value);
+
+    public static @NotNull ItemTag<Integer> Integer(@NotNull String key) {
+        return new ItemTag<>(key) {
+            @Override
+            protected Integer read(@NotNull NBTCompound nbtCompound) {
+                return nbtCompound.getInt(key);
+            }
+
+            @Override
+            protected void write(@NotNull NBTCompound nbtCompound, @NotNull Integer value) {
+                nbtCompound.setInt(key, value);
+            }
+        };
+    }
+
+}

src/test/java/demo/PlayerInit.java

@@ -27,6 +27,7 @@ import net.minestom.server.inventory.Inventory;
 import net.minestom.server.inventory.InventoryType;
 import net.minestom.server.inventory.PlayerInventory;
 import net.minestom.server.item.ItemStack;
+import net.minestom.server.item.ItemTag;
 import net.minestom.server.item.Material;
 import net.minestom.server.item.meta.CompassMeta;
 import net.minestom.server.network.ConnectionManager;
@@ -69,12 +70,10 @@ public class PlayerInit {
                     .build();
 
             ItemStack itemStack = ItemStack.builder(Material.COMPASS)
-                    .amount(5)
-                    .meta(compassMeta)
                     .meta(CompassMeta.class, builder -> {
                         builder.lodestonePosition(new Position(0, 0, 0));
+                        builder.set(ItemTag.Integer("int"), 25);
                     })
-                    .displayName(Component.text("displayName"))
                     .build();
 
             itemStack = itemStack.with(itemBuilder -> itemBuilder
@@ -225,8 +224,8 @@ public class PlayerInit {
 
             PlayerInventory inventory = player.getInventory();
             ItemStack itemStack = ItemStack.of(Material.STONE, 64);
-            inventory.addItemStack(itemStack);
+            inventory.addItemStack(itemStack.withMeta(metaBuilder -> metaBuilder.set(ItemTag.Integer("int"), 25)));
-            inventory.replaceItemStack(0, i -> i.withAmount(32));
+            //inventory.replaceItemStack(0, i -> i.withAmount(32));
 
             {
                 ItemStack item = ItemStack.builder(Material.DIAMOND_CHESTPLATE)