Initial reusable meta builder

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

@@ -51,7 +51,7 @@ public class ItemMeta implements TagReadable, Writeable {
         this.canDestroy = new HashSet<>(metaBuilder.canDestroy);
         this.canPlaceOn = new HashSet<>(metaBuilder.canPlaceOn);
 
-        this.nbt = metaBuilder.nbt;
+        this.nbt = metaBuilder.nbt();
         this.emptyBuilder = metaBuilder.getSupplier().get();
     }
 

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

@@ -2,7 +2,6 @@ package net.minestom.server.item;
 
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.serializer.gson.GsonComponentSerializer;
-import net.minestom.server.adventure.AdventureSerializer;
 import net.minestom.server.instance.block.Block;
 import net.minestom.server.item.attribute.ItemAttribute;
 import net.minestom.server.tag.Tag;
@@ -15,12 +14,17 @@ import org.jetbrains.annotations.Nullable;
 import org.jglrxavpok.hephaistos.nbt.*;
 
 import java.util.*;
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 
 public abstract class ItemMetaBuilder implements TagWritable {
 
-    protected NBTCompound nbt = new NBTCompound();
+    private static final AtomicReferenceFieldUpdater<ItemMetaBuilder, NBTCompound> NBT_UPDATER =
+            AtomicReferenceFieldUpdater.newUpdater(ItemMetaBuilder.class, NBTCompound.class, "nbt");
+
+    protected volatile boolean built = false;
+    private volatile NBTCompound nbt = new NBTCompound();
 
     protected int damage;
     protected boolean unbreakable;
@@ -36,21 +40,21 @@ public abstract class ItemMetaBuilder implements TagWritable {
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder damage(int damage) {
         this.damage = damage;
-        this.nbt.setInt("Damage", damage);
+        mutateNbt(compound -> compound.setInt("Damage", damage));
         return this;
     }
 
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder unbreakable(boolean unbreakable) {
         this.unbreakable = unbreakable;
-        this.nbt.setByte("Unbreakable", (byte) (unbreakable ? 1 : 0));
+        mutateNbt(compound -> compound.setByte("Unbreakable", (byte) (unbreakable ? 1 : 0)));
         return this;
     }
 
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder hideFlag(int hideFlag) {
         this.hideFlag = hideFlag;
-        this.nbt.setInt("HideFlags", hideFlag);
+        mutateNbt(compound -> compound.setInt("HideFlags", hideFlag));
         return this;
     }
 
@@ -79,7 +83,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder lore(@NotNull List<@NotNull Component> lore) {
-        this.lore = lore;
+        this.lore = new ArrayList<>(lore);
         handleCompound("display", nbtCompound -> {
             final NBTList<NBTString> loreNBT = new NBTList<>(NBTTypes.TAG_String);
             for (Component line : lore) {
@@ -98,7 +102,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder enchantments(@NotNull Map<Enchantment, Short> enchantments) {
-        this.enchantmentMap = enchantments;
+        this.enchantmentMap = new HashMap<>(enchantments);
         handleMap(enchantmentMap, "Enchantments", nbt, () -> {
             NBTUtils.writeEnchant(nbt, "Enchantments", enchantmentMap);
             return nbt.get("Enchantments");
@@ -108,21 +112,21 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     @Contract("_, _ -> this")
     public @NotNull ItemMetaBuilder enchantment(@NotNull Enchantment enchantment, short level) {
-        this.enchantmentMap.put(enchantment, level);
+        this.enchantmentMap = Map.of(enchantment, level);
         enchantments(enchantmentMap);
         return this;
     }
 
     @Contract("-> this")
     public @NotNull ItemMetaBuilder clearEnchantment() {
-        this.enchantmentMap.clear();
+        this.enchantmentMap = Collections.emptyMap();
         enchantments(enchantmentMap);
         return this;
     }
 
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder attributes(@NotNull List<@NotNull ItemAttribute> attributes) {
-        this.attributes = attributes;
+        this.attributes = new ArrayList<>(attributes);
 
         handleCollection(attributes, "AttributeModifiers", nbt, () -> {
             NBTList<NBTCompound> attributesNBT = new NBTList<>(NBTTypes.TAG_Compound);
@@ -153,7 +157,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder canPlaceOn(@NotNull Set<@NotNull Block> blocks) {
-        this.canPlaceOn = blocks;
+        this.canPlaceOn = new HashSet<>(blocks);
         handleCollection(canPlaceOn, "CanPlaceOn", nbt, () -> {
             NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
             canPlaceOn.forEach(block -> list.add(new NBTString(block.getName())));
@@ -170,7 +174,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     @Contract("_ -> this")
     public @NotNull ItemMetaBuilder canDestroy(@NotNull Set<@NotNull Block> blocks) {
-        this.canDestroy = blocks;
+        this.canDestroy = new HashSet<>(blocks);
         handleCollection(canDestroy, "CanDestroy", nbt, () -> {
             NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
             canDestroy.forEach(block -> list.add(new NBTString(block.getName())));
@@ -187,7 +191,7 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     @Override
     public <T> void setTag(@NotNull Tag<T> tag, @Nullable T value) {
-        tag.write(nbt, value);
+        mutateNbt(compound -> tag.write(compound, value));
     }
 
     public <T> @NotNull ItemMetaBuilder set(@NotNull Tag<T> tag, @Nullable T value) {
@@ -202,30 +206,51 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     protected abstract @NotNull Supplier<@NotNull ItemMetaBuilder> getSupplier();
 
+    protected void mutateNbt(Consumer<NBTCompound> consumer) {
+        if (built) {
+            built = false;
+            final var currentNbt = nbt;
+            NBT_UPDATER.compareAndSet(this, currentNbt, currentNbt.deepClone());
+        }
+        synchronized (this) {
+            consumer.accept(nbt);
+        }
+    }
+
+    protected synchronized NBTCompound nbt() {
+        return nbt;
+    }
+
+    protected @NotNull ItemMeta generate() {
+        this.built = true;
+        return build();
+    }
+
     protected void handleCompound(@NotNull String key,
                                   @NotNull Consumer<@NotNull NBTCompound> consumer) {
-        NBTCompound compound = null;
+        mutateNbt(nbt -> {
-        boolean newNbt = false;
+            NBTCompound compound = null;
-        if (nbt.containsKey(key)) {
+            boolean newNbt = false;
-            NBT dNbt = nbt.get(key);
+            if (nbt.containsKey(key)) {
-            if (dNbt instanceof NBTCompound) {
+                NBT dNbt = nbt.get(key);
-                compound = (NBTCompound) dNbt;
+                if (dNbt instanceof NBTCompound) {
-            }
+                    compound = (NBTCompound) dNbt;
-        } else {
+                }
-            compound = new NBTCompound();
+            } else {
-            newNbt = true;
+                compound = new NBTCompound();
-        }
+                newNbt = true;
-
-        if (compound != null) {
-            consumer.accept(compound);
-
-            if (newNbt && compound.getSize() > 0) {
-                this.nbt.set(key, compound);
-            } else if (!newNbt && compound.getSize() == 0) {
-                this.nbt.removeTag(key);
             }
 
-        }
+            if (compound != null) {
+                consumer.accept(compound);
+
+                if (newNbt && compound.getSize() > 0) {
+                    this.nbt.set(key, compound);
+                } else if (!newNbt && compound.getSize() == 0) {
+                    this.nbt.removeTag(key);
+                }
+            }
+        });
     }
 
     protected void handleNullable(@Nullable Object value,
@@ -239,6 +264,12 @@ public abstract class ItemMetaBuilder implements TagWritable {
         }
     }
 
+    protected void handleNullable(@Nullable Object value,
+                                  @NotNull String key,
+                                  @NotNull Supplier<@NotNull NBT> supplier) {
+        mutateNbt(compound -> handleNullable(value, key, compound, supplier));
+    }
+
     protected void handleCollection(@NotNull Collection<?> objects,
                                     @NotNull String key,
                                     @NotNull NBTCompound nbtCompound,
@@ -250,6 +281,12 @@ public abstract class ItemMetaBuilder implements TagWritable {
         }
     }
 
+    protected void handleCollection(@NotNull Collection<?> objects,
+                                    @NotNull String key,
+                                    @NotNull Supplier<@NotNull NBT> supplier) {
+        mutateNbt(compound -> handleCollection(objects, key, compound, supplier));
+    }
+
     protected void handleMap(@NotNull Map<?, ?> objects,
                              @NotNull String key,
                              @NotNull NBTCompound nbtCompound,
@@ -271,5 +308,4 @@ public abstract class ItemMetaBuilder implements TagWritable {
 
     public interface Provider<T extends ItemMetaBuilder> {
     }
-
 }

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

@@ -109,9 +109,9 @@ public class ItemStackBuilder {
 
     @Contract(value = "-> new", pure = true)
     public @NotNull ItemStack build() {
-        if (amount > 0)
+        if (amount < 1)
-            return new ItemStack(material, amount, metaBuilder.build(), stackingRule);
+            return ItemStack.AIR;
-        return ItemStack.AIR;
+        return new ItemStack(material, amount, metaBuilder.generate(), stackingRule);
     }
 
     private static final class DefaultMeta extends ItemMetaBuilder {
@@ -130,5 +130,4 @@ public class ItemStackBuilder {
             return DefaultMeta::new;
         }
     }
-
 }

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

@@ -45,18 +45,20 @@ public class CompassMeta extends ItemMeta implements ItemMetaBuilder.Provider<Co
 
         public Builder lodestoneTracked(boolean lodestoneTracked) {
             this.lodestoneTracked = lodestoneTracked;
-            this.nbt.setByte("LodestoneTracked", (byte) (lodestoneTracked ? 1 : 0));
+            mutateNbt(compound -> compound.setByte("LodestoneTracked", (byte) (lodestoneTracked ? 1 : 0)));
             return this;
         }
 
         public Builder lodestoneDimension(@Nullable String lodestoneDimension) {
             this.lodestoneDimension = lodestoneDimension;
 
-            if (lodestoneDimension != null) {
+            mutateNbt(compound -> {
-                this.nbt.setString("LodestoneDimension", lodestoneDimension);
+                if (lodestoneDimension != null) {
-            } else {
+                    compound.setString("LodestoneDimension", lodestoneDimension);
-                this.nbt.removeTag("LodestoneDimension");
+                } else {
-            }
+                    compound.removeTag("LodestoneDimension");
+                }
+            });
 
             return this;
         }
@@ -64,15 +66,17 @@ public class CompassMeta extends ItemMeta implements ItemMetaBuilder.Provider<Co
         public Builder lodestonePosition(@Nullable Position lodestonePosition) {
             this.lodestonePosition = lodestonePosition;
 
-            if (lodestonePosition != null) {
+            mutateNbt(compound -> {
-                NBTCompound posCompound = new NBTCompound();
+                if (lodestonePosition != null) {
-                posCompound.setInt("X", (int) lodestonePosition.getX());
+                    NBTCompound posCompound = new NBTCompound();
-                posCompound.setInt("Y", (int) lodestonePosition.getY());
+                    posCompound.setInt("X", (int) lodestonePosition.getX());
-                posCompound.setInt("Z", (int) lodestonePosition.getZ());
+                    posCompound.setInt("Y", (int) lodestonePosition.getY());
-                this.nbt.set("LodestonePos", posCompound);
+                    posCompound.setInt("Z", (int) lodestonePosition.getZ());
-            } else {
+                    compound.set("LodestonePos", posCompound);
-                this.nbt.removeTag("LodestonePos");
+                } else {
-            }
+                    compound.removeTag("LodestonePos");
+                }
+            });
 
             return this;
         }

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

@@ -97,7 +97,7 @@ public class CrossbowMeta extends ItemMeta implements ItemMetaBuilder.Provider<S
             if (!projectile.isAir()) {
                 chargedProjectiles.add(getItemCompound(projectile));
             }
-            this.nbt.set("ChargedProjectiles", chargedProjectiles);
+            mutateNbt(compound -> compound.set("ChargedProjectiles", chargedProjectiles));
 
             return this;
         }
@@ -123,7 +123,7 @@ public class CrossbowMeta extends ItemMeta implements ItemMetaBuilder.Provider<S
             chargedProjectiles.add(getItemCompound(projectile1));
             chargedProjectiles.add(getItemCompound(projectile2));
             chargedProjectiles.add(getItemCompound(projectile3));
-            this.nbt.set("ChargedProjectiles", chargedProjectiles);
+            mutateNbt(compound -> compound.set("ChargedProjectiles", chargedProjectiles));
 
             return this;
         }
@@ -135,7 +135,7 @@ public class CrossbowMeta extends ItemMeta implements ItemMetaBuilder.Provider<S
          */
         public Builder charged(boolean charged) {
             this.charged = charged;
-            this.nbt.setByte("Charged", (byte) (charged ? 1 : 0));
+            mutateNbt(compound -> compound.setByte("Charged", (byte) (charged ? 1 : 0)));
             return this;
         }
 

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

@@ -35,13 +35,13 @@ public class EnchantedBookMeta extends ItemMeta implements ItemMetaBuilder.Provi
 
         private Map<Enchantment, Short> enchantments = new HashMap<>();
 
-        public @NotNull Builder enchantments(Map<Enchantment, Short> enchantments) {
+        public @NotNull Builder enchantments(@NotNull Map<Enchantment, Short> enchantments) {
             this.enchantments = enchantments;
-            NBTUtils.writeEnchant(nbt, "StoredEnchantments", enchantments);
+            mutateNbt(compound -> NBTUtils.writeEnchant(compound, "StoredEnchantments", enchantments));
             return this;
         }
 
-        public @NotNull Builder enchantment(Enchantment enchantment, short level) {
+        public @NotNull Builder enchantment(@NotNull Enchantment enchantment, short level) {
             this.enchantments.put(enchantment, level);
             enchantments(enchantments);
             return this;

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

@@ -28,7 +28,7 @@ public class FireworkEffectMeta extends ItemMeta implements ItemMetaBuilder.Prov
 
         public Builder effect(@Nullable FireworkEffect fireworkEffect) {
             this.fireworkEffect = fireworkEffect;
-            this.nbt.set("Explosion", this.fireworkEffect.asCompound());
+            mutateNbt(compound -> compound.set("Explosion", this.fireworkEffect.asCompound()));
             return this;
         }
 

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

@@ -91,18 +91,18 @@ public class MapMeta extends ItemMeta implements ItemMetaBuilder.Provider<MapMet
 
         public Builder mapId(int value) {
             this.mapId = value;
-            this.nbt.setInt("map", mapId);
+            mutateNbt(compound -> compound.setInt("map", mapId));
             return this;
         }
 
         public Builder mapScaleDirection(int value) {
             this.mapScaleDirection = value;
-            this.nbt.setInt("map_scale_direction", value);
+            mutateNbt(compound -> compound.setInt("map_scale_direction", value));
             return this;
         }
 
         public Builder decorations(List<MapDecoration> value) {
-            this.decorations = value;
+            this.decorations = new ArrayList<>(value);
 
             NBTList<NBTCompound> decorationsList = new NBTList<>(NBTTypes.TAG_Compound);
             for (MapDecoration decoration : decorations) {
@@ -115,7 +115,7 @@ public class MapMeta extends ItemMeta implements ItemMetaBuilder.Provider<MapMet
 
                 decorationsList.add(decorationCompound);
             }
-            this.nbt.set("Decorations", decorationsList);
+            mutateNbt(compound -> compound.set("Decorations", decorationsList));
 
             return this;
         }
@@ -123,14 +123,16 @@ public class MapMeta extends ItemMeta implements ItemMetaBuilder.Provider<MapMet
         public Builder mapColor(Color value) {
             this.mapColor = value;
 
-            NBTCompound displayCompound;
+            mutateNbt(nbt -> {
-            if (nbt.containsKey("display")) {
+                NBTCompound displayCompound;
-                displayCompound = nbt.getCompound("display");
+                if (nbt.containsKey("display")) {
-            } else {
+                    displayCompound = nbt.getCompound("display");
-                displayCompound = new NBTCompound();
+                } else {
-                this.nbt.set("display", displayCompound);
+                    displayCompound = new NBTCompound();
-            }
+                    nbt.set("display", displayCompound);
-            displayCompound.setInt("MapColor", mapColor.asRGB());
+                }
+                displayCompound.setInt("MapColor", mapColor.asRGB());
+            });
 
             return this;
         }

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

@@ -52,7 +52,7 @@ public class PotionMeta extends ItemMeta implements ItemMetaBuilder.Provider<Pot
 
         public Builder potionType(@NotNull PotionType potionType) {
             this.potionType = potionType;
-            this.nbt.setString("Potion", potionType.getNamespaceID().asString());
+            mutateNbt(compound -> compound.setString("Potion", potionType.getNamespaceID().asString()));
             return this;
         }
 
@@ -71,14 +71,14 @@ public class PotionMeta extends ItemMeta implements ItemMetaBuilder.Provider<Pot
 
                 potionList.add(potionCompound);
             }
-            this.nbt.set("CustomPotionEffects", potionList);
+            mutateNbt(compound -> compound.set("CustomPotionEffects", potionList));
 
             return this;
         }
 
         public Builder color(@NotNull Color color) {
             this.color = color;
-            this.nbt.setInt("CustomPotionColor", color.asRGB());
+            mutateNbt(compound -> compound.setInt("CustomPotionColor", color.asRGB()));
             return this;
         }
 

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

@@ -2,7 +2,6 @@ package net.minestom.server.item.metadata;
 
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.serializer.gson.GsonComponentSerializer;
-import net.minestom.server.adventure.AdventureSerializer;
 import net.minestom.server.item.ItemMeta;
 import net.minestom.server.item.ItemMetaBuilder;
 import org.jetbrains.annotations.NotNull;
@@ -53,22 +52,22 @@ public class WritableBookMeta extends ItemMeta implements ItemMetaBuilder.Provid
 
         public Builder author(@Nullable String author) {
             this.author = author;
-            handleNullable(author, "author", nbt,
+            handleNullable(author, "author",
                     () -> new NBTString(Objects.requireNonNull(author)));
             return this;
         }
 
         public Builder title(@Nullable String title) {
             this.title = title;
-            handleNullable(title, "title", nbt,
+            handleNullable(title, "title",
                     () -> new NBTString(Objects.requireNonNull(title)));
             return this;
         }
 
         public Builder pages(@NotNull List<@NotNull Component> pages) {
-            this.pages = pages;
+            this.pages = new ArrayList<>(pages);
 
-            handleCollection(pages, "pages", nbt, () -> {
+            handleCollection(pages, "pages", () -> {
                 NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
                 for (Component page : pages) {
                     list.add(new NBTString(GsonComponentSerializer.gson().serialize(page)));

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

@@ -86,35 +86,35 @@ public class WrittenBookMeta extends ItemMeta implements ItemMetaBuilder.Provide
 
         public Builder resolved(boolean resolved) {
             this.resolved = resolved;
-            this.nbt.setByte("resolved", (byte) (resolved ? 1 : 0));
+            mutateNbt(compound -> compound.setByte("resolved", (byte) (resolved ? 1 : 0)));
             return this;
         }
 
         public Builder generation(@Nullable WrittenBookGeneration generation) {
             this.generation = generation;
-            handleNullable(generation, "generation", nbt,
+            handleNullable(generation, "generation",
                     () -> new NBTInt(Objects.requireNonNull(generation).ordinal()));
             return this;
         }
 
         public Builder author(@Nullable String author) {
             this.author = author;
-            handleNullable(author, "author", nbt,
+            handleNullable(author, "author",
                     () -> new NBTString(Objects.requireNonNull(author)));
             return this;
         }
 
         public Builder title(@Nullable String title) {
             this.title = title;
-            handleNullable(title, "title", nbt,
+            handleNullable(title, "title",
                     () -> new NBTString(Objects.requireNonNull(title)));
             return this;
         }
 
         public Builder pages(@NotNull List<@NotNull Component> pages) {
-            this.pages = pages;
+            this.pages = new ArrayList<>(pages);
 
-            handleCollection(pages, "pages", nbt, () -> {
+            handleCollection(pages, "pages", () -> {
                 NBTList<NBTString> list = new NBTList<>(NBTTypes.TAG_String);
                 for (Component page : pages) {
                     list.add(new NBTString(GsonComponentSerializer.gson().serialize(page)));