Improve Registry

paper-server/src/main/java/org/bukkit/craftbukkit/CraftRegistry.java

@@ -184,6 +184,7 @@ public class CraftRegistry<B extends Keyed, M> implements Registry<B> {
 
     private final Class<?> bukkitClass; // Paper - relax preload class
     private final Map<NamespacedKey, B> cache = new HashMap<>();
+    private final Map<B, NamespacedKey> byValue = new java.util.IdentityHashMap<>(); // Paper - improve Registry
     private final net.minecraft.core.Registry<M> minecraftRegistry;
     private final io.papermc.paper.registry.entry.RegistryTypeMapper<M, B> minecraftToBukkit; // Paper - switch to Holder
     private final BiFunction<NamespacedKey, ApiVersion, NamespacedKey> serializationUpdater; // Paper - rename to make it *clear* what it is *only* for
@@ -237,6 +238,7 @@ public class CraftRegistry<B extends Keyed, M> implements Registry<B> {
         }
 
         this.cache.put(namespacedKey, bukkit);
+        this.byValue.put(bukkit, namespacedKey); // Paper - improve Registry
 
         return bukkit;
     }
@@ -279,4 +281,11 @@ public class CraftRegistry<B extends Keyed, M> implements Registry<B> {
         return this.minecraftToBukkit.convertDirectHolder(holder);
     }
     // Paper end - support Direct Holders
+
+    // Paper start - improve Registry
+    @Override
+    public NamespacedKey getKey(final B value) {
+        return this.byValue.get(value);
+    }
+    // Paper end - improve Registry
 }