Added NBTConsumer for custom item nbt

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

@@ -1,5 +1,6 @@
 package net.minestom.server.item;
 
+import com.google.gson.JsonObject;
 import net.minestom.server.chat.ColoredText;
 import net.minestom.server.data.Data;
 import net.minestom.server.data.DataContainer;
@@ -40,6 +41,8 @@ public class ItemStack implements DataContainer {
     private StackingRule stackingRule;
     private Data data;
 
+    private NBTConsumer nbtConsumer;
+
     {
         if (defaultStackingRule == null)
             defaultStackingRule = DEFAULT_STACKING_RULE;
@@ -513,6 +516,29 @@ public class ItemStack implements DataContainer {
         return itemStack;
     }
 
+    /**
+     * Convert the item into a readable Json object
+     * <p>
+     * Mainly used to show an item in a message hover
+     *
+     * @return a {@link JsonObject} containing the item data
+     */
+    public synchronized JsonObject toJsonObject() {
+        JsonObject object = new JsonObject();
+        object.addProperty("id", getMaterialId());
+        object.addProperty("Damage", getDamage());
+        object.addProperty("Count", getAmount());
+
+        if (hasDisplayName() || hasLore()) {
+            JsonObject tagObject = new JsonObject();
+            if (hasDisplayName()) {
+                tagObject.addProperty("display", getDisplayName().toString());
+            }
+        }
+
+        return object;
+    }
+
     @Override
     public Data getData() {
         return data;
@@ -523,6 +549,24 @@ public class ItemStack implements DataContainer {
         this.data = data;
     }
 
+    /**
+     * Get the nbt consumer called when the item is serialized into a packet
+     *
+     * @return the item nbt consumer, null if not any
+     */
+    public NBTConsumer getNBTConsumer() {
+        return nbtConsumer;
+    }
+
+    /**
+     * Change the item nbt consumer
+     *
+     * @param nbtConsumer the new item nbt consumer
+     */
+    public void setNBTConsumer(NBTConsumer nbtConsumer) {
+        this.nbtConsumer = nbtConsumer;
+    }
+
     /**
      * Get the item stacking rule
      *

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

@@ -0,0 +1,8 @@
+package net.minestom.server.item;
+
+import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+
+import java.util.function.Consumer;
+
+public interface NBTConsumer extends Consumer<NBTCompound> {
+}

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

@@ -8,6 +8,7 @@ import net.minestom.server.inventory.Inventory;
 import net.minestom.server.item.Enchantment;
 import net.minestom.server.item.ItemStack;
 import net.minestom.server.item.Material;
+import net.minestom.server.item.NBTConsumer;
 import net.minestom.server.item.attribute.AttributeSlot;
 import net.minestom.server.item.attribute.ItemAttribute;
 import net.minestom.server.network.packet.PacketReader;
@@ -28,6 +29,7 @@ public class NBTUtils {
 
     /**
      * Loads all the items from the 'items' list into the given inventory
+     *
      * @param items
      * @param destination
      */
@@ -192,7 +194,16 @@ public class NBTUtils {
             }
 
             NBTCompound itemNBT = new NBTCompound();
+
+            // Vanilla compound
             saveDataIntoNBT(itemStack, itemNBT);
+
+            // Custom item nbt
+            NBTConsumer nbtConsumer = itemStack.getNBTConsumer();
+            if (nbtConsumer != null) {
+                nbtConsumer.accept(itemNBT);
+            }
+
             // End custom model data
             packet.writeNBT("", itemNBT);
         }