add BundleMeta and full item to/from nbt

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

@@ -7,6 +7,7 @@ import net.minestom.server.item.rule.VanillaStackingRule;
 import net.minestom.server.tag.Tag;
 import net.minestom.server.tag.TagReadable;
 import net.minestom.server.utils.NBTUtils;
+import net.minestom.server.utils.validate.Check;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
@@ -79,6 +80,18 @@ public final class ItemStack implements TagReadable, HoverEventSource<HoverEvent
         return fromNBT(material, nbtCompound, 1);
     }
 
+    public static @NotNull ItemStack fromItemNBT(@NotNull NBTCompound nbtCompound) {
+        String id = nbtCompound.getString("id");
+        Check.notNull(id, "Item NBT must contain an id field.");
+        Material material = Material.fromNamespaceId(id);
+        Check.notNull(material, "Unknown material: " + id);
+
+        Byte amount = nbtCompound.getByte("Count");
+        return fromNBT(material,
+                nbtCompound.getCompound("tag"),
+                amount == null ? 0 : amount);
+    }
+
     @Contract(pure = true)
     public @NotNull Material getMaterial() {
         return material;
@@ -228,6 +241,14 @@ public final class ItemStack implements TagReadable, HoverEventSource<HoverEvent
                 NBTUtils.asBinaryTagHolder(this.meta.toNBT().getCompound("tag")))));
     }
 
+    public @NotNull NBTCompound toItemNBT() {
+        final NBTCompound nbtCompound = new NBTCompound();
+        nbtCompound.setString("id", getMaterial().namespace().asString());
+        nbtCompound.setByte("Count", (byte) getAmount());
+        nbtCompound.set("tag", getMeta().toNBT());
+        return nbtCompound;
+    }
+
     @Contract(value = "-> new", pure = true)
     private @NotNull ItemStackBuilder builder() {
         return new ItemStackBuilder(material, meta.builder())

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

@@ -46,6 +46,7 @@ public class ItemStackBuilder {
         MATERIAL_SUPPLIER_MAP.put(Material.FIREWORK_STAR, FireworkEffectMeta.Builder::new);
         MATERIAL_SUPPLIER_MAP.put(Material.FIREWORK_ROCKET, FireworkMeta.Builder::new);
         MATERIAL_SUPPLIER_MAP.put(Material.PLAYER_HEAD, PlayerHeadMeta.Builder::new);
+        MATERIAL_SUPPLIER_MAP.put(Material.BUNDLE, BundleMeta.Builder::new);
 
         MATERIAL_SUPPLIER_MAP.put(Material.LEATHER_HELMET, LeatherArmorMeta.Builder::new);
         MATERIAL_SUPPLIER_MAP.put(Material.LEATHER_CHESTPLATE, LeatherArmorMeta.Builder::new);

src/main/java/net/minestom/server/item/metadata/BundleMeta.java

@@ -0,0 +1,82 @@
+package net.minestom.server.item.metadata;
+
+import net.minestom.server.item.ItemMeta;
+import net.minestom.server.item.ItemMetaBuilder;
+import net.minestom.server.item.ItemStack;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+import org.jglrxavpok.hephaistos.nbt.NBTList;
+import org.jglrxavpok.hephaistos.nbt.NBTTypes;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Supplier;
+
+public class BundleMeta extends ItemMeta implements ItemMetaBuilder.Provider<BundleMeta.Builder> {
+
+    private final List<ItemStack> items;
+
+    protected BundleMeta(ItemMetaBuilder metaBuilder,
+                         @NotNull List<ItemStack> items) {
+        super(metaBuilder);
+        this.items = List.copyOf(items);
+    }
+
+    public @NotNull List<ItemStack> getItems() {
+        return items;
+    }
+
+    public static class Builder extends ItemMetaBuilder {
+        private List<ItemStack> items = new ArrayList<>();
+
+        public Builder items(@NotNull List<ItemStack> items) {
+            this.items = items;
+            updateItems();
+            return this;
+        }
+
+        public Builder addItem(@NotNull ItemStack item) {
+            items.add(item);
+            updateItems();
+            return this;
+        }
+
+        public Builder removeItem(@NotNull ItemStack item) {
+            items.remove(item);
+            updateItems();
+            return this;
+        }
+
+        @Override
+        public @NotNull BundleMeta build() {
+            return new BundleMeta(this, items);
+        }
+
+        private void updateItems() {
+            mutateNbt(compound -> {
+                NBTList<NBTCompound> itemList = new NBTList<>(NBTTypes.TAG_Compound);
+                for (ItemStack item : items) {
+                    itemList.add(item.toItemNBT());
+                }
+                compound.set("Items", itemList);
+            });
+        }
+
+        @Override
+        public void read(@NotNull NBTCompound nbtCompound) {
+            if (nbtCompound.containsKey("Items")) {
+                final NBTList<NBTCompound> items = nbtCompound.getList("Items");
+                for (NBTCompound item : items) {
+                    this.items.add(ItemStack.fromItemNBT(item));
+                }
+            }
+        }
+
+        @Override
+        protected @NotNull Supplier<@NotNull ItemMetaBuilder> getSupplier() {
+            return Builder::new;
+        }
+    }
+}

src/test/java/demo/PlayerInit.java

@@ -29,6 +29,7 @@ import net.minestom.server.inventory.Inventory;
 import net.minestom.server.inventory.InventoryType;
 import net.minestom.server.item.ItemStack;
 import net.minestom.server.item.Material;
+import net.minestom.server.item.metadata.BundleMeta;
 import net.minestom.server.monitoring.BenchmarkManager;
 import net.minestom.server.monitoring.TickMonitor;
 import net.minestom.server.utils.MathUtils;
@@ -104,6 +105,14 @@ public class PlayerInit {
                                         .canDestroy(Set.of(Block.DIAMOND_ORE)))
                         .build();
                 player.getInventory().addItemStack(itemStack);
+
+                ItemStack bundle = ItemStack.builder(Material.BUNDLE)
+                        .meta(BundleMeta.class, bundleMetaBuilder -> {
+                            bundleMetaBuilder.addItem(ItemStack.builder(Material.DIAMOND).amount(5).build());
+                            bundleMetaBuilder.addItem(ItemStack.builder(Material.RABBIT_FOOT).amount(5).build());
+                        })
+                        .build();
+                player.getInventory().addItemStack(bundle);
             });
 
     static {