item meta cleanup

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

@@ -1,11 +1,54 @@
 package net.minestom.server.item.metadata;
 
-public abstract class ItemMeta {
+import net.minestom.server.item.ItemStack;
+import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
-    public abstract boolean hasNbt();
+/**
+ * Represent nbt data only available for a type of item
+ */
+public interface ItemMeta {
 
-    public abstract boolean isSimilar(ItemMeta itemMeta);
+    /**
+     * Get if this meta object contains any useful data to send to the client
+     *
+     * @return true if this item has nbt data, false otherwise
+     */
+    boolean hasNbt();
 
-    public abstract ItemMeta clone();
+    /**
+     * Get if the two ItemMeta are similar
+     * <p>
+     * It is used by {@link ItemStack#isSimilar(ItemStack)}
+     *
+     * @param itemMeta the second item meta to check
+     * @return true if the two meta are similar, false otherwise
+     */
+    boolean isSimilar(ItemMeta itemMeta);
+
+    /**
+     * Read nbt data from a compound
+     * <p>
+     * WARNING: it is possible that it contains no useful data,
+     * it has to be checked before getting anything
+     *
+     * @param compound the compound containing the data
+     */
+    void read(NBTCompound compound);
+
+    /**
+     * Write nbt data to a compound
+     *
+     * @param compound the compound receiving the item meta data
+     */
+    void write(NBTCompound compound);
+
+    /**
+     * Clone this item meta
+     * <p>
+     * Used by {@link ItemStack#clone()}
+     *
+     * @return the cloned item meta
+     */
+    ItemMeta clone();
 
 }

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

@@ -1,6 +1,8 @@
 package net.minestom.server.item.metadata;
 
-public class MapMeta extends ItemMeta {
+import org.jglrxavpok.hephaistos.nbt.NBTCompound;
+
+public class MapMeta implements ItemMeta {
 
     private int mapId;
 
@@ -22,6 +24,20 @@ public class MapMeta extends ItemMeta {
         return itemMeta instanceof MapMeta && ((MapMeta) itemMeta).getMapId() == mapId;
     }
 
+    @Override
+    public void read(NBTCompound compound) {
+        if (compound.containsKey("map")) {
+            this.mapId = compound.getInt("map");
+        }
+    }
+
+    @Override
+    public void write(NBTCompound compound) {
+        if (mapId != 0) {
+            compound.setInt("map", mapId);
+        }
+    }
+
     @Override
     public ItemMeta clone() {
         MapMeta mapMeta = new MapMeta();

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

@@ -1,12 +1,14 @@
 package net.minestom.server.item.metadata;
 
 import net.minestom.server.potion.PotionType;
+import net.minestom.server.registry.Registries;
+import org.jglrxavpok.hephaistos.nbt.NBTCompound;
 
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
-public class PotionMeta extends ItemMeta {
+public class PotionMeta implements ItemMeta {
 
     private Set<PotionType> potionTypes = new HashSet<>();
 
@@ -47,6 +49,22 @@ public class PotionMeta extends ItemMeta {
         return itemMeta instanceof PotionMeta && ((PotionMeta) itemMeta).potionTypes.equals(potionTypes);
     }
 
+    @Override
+    public void read(NBTCompound compound) {
+        if (compound.containsKey("Potion")) {
+            addPotionType(Registries.getPotionType(compound.getString("Potion")));
+        }
+    }
+
+    @Override
+    public void write(NBTCompound compound) {
+        if (!potionTypes.isEmpty()) {
+            for (PotionType potionType : potionTypes) {
+                compound.setString("Potion", potionType.getNamespaceID());
+            }
+        }
+    }
+
     @Override
     public ItemMeta clone() {
         PotionMeta potionMeta = new PotionMeta();

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

@@ -12,18 +12,18 @@ import net.minestom.server.item.NBTConsumer;
 import net.minestom.server.item.attribute.AttributeSlot;
 import net.minestom.server.item.attribute.ItemAttribute;
 import net.minestom.server.item.metadata.ItemMeta;
-import net.minestom.server.item.metadata.MapMeta;
-import net.minestom.server.item.metadata.PotionMeta;
 import net.minestom.server.network.packet.PacketReader;
 import net.minestom.server.network.packet.PacketWriter;
-import net.minestom.server.potion.PotionType;
 import net.minestom.server.registry.Registries;
 import org.jglrxavpok.hephaistos.nbt.*;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
 
 // for lack of a better name
 public class NBTUtils {
@@ -172,19 +172,7 @@ public class NBTUtils {
         final ItemMeta itemMeta = item.getItemMeta();
         if (itemMeta == null)
             return;
-        final Class metaType = itemMeta.getClass();
-        if (metaType == PotionMeta.class) {
-            final PotionMeta potionMeta = (PotionMeta) itemMeta;
-            if (nbt.containsKey("Potion")) {
-                potionMeta.addPotionType(Registries.getPotionType(nbt.getString("Potion")));
-            }
-        } else if (metaType == MapMeta.class) {
-            final MapMeta mapMeta = (MapMeta) itemMeta;
-            if (nbt.containsKey("map")) {
-                mapMeta.setMapId(nbt.getInt("map"));
-            }
-        }
-
+        itemMeta.read(nbt);
     }
 
     private static void loadEnchantments(NBTList<NBTCompound> enchantments, EnchantmentSetter setter) {
@@ -324,26 +312,14 @@ public class NBTUtils {
                 itemNBT.setInt("CustomModelData", customModelData);
             }
         }
+        // End custom model data
 
         // Start custom meta
         final ItemMeta itemMeta = itemStack.getItemMeta();
         if (itemMeta != null) {
-            final Class metaType = itemMeta.getClass();
-            if (metaType == PotionMeta.class) {
-                final Set<PotionType> potionTypes = ((PotionMeta) itemMeta).getPotionTypes();
-                if (!potionTypes.isEmpty()) {
-                    for (PotionType potionType : potionTypes) {
-                        itemNBT.setString("Potion", potionType.getNamespaceID());
-                    }
-                }
-            } else if (metaType == MapMeta.class) {
-                final int mapId = ((MapMeta) itemMeta).getMapId();
-                if (mapId != 0) {
-                    itemNBT.setInt("map", mapId);
-                }
-            }
-
+            itemMeta.write(itemNBT);
         }
+        // End custom meta
     }
 
     @FunctionalInterface