Add enum (de)serialisation support

src/main/java/de/bluecolored/bluenbt/BlueNBT.java

@@ -75,6 +75,7 @@ public BlueNBT() {
         register(ArrayAdapterFactory.INSTANCE);
         register(PrimitiveSerializerFactory.INSTANCE);
         register(PrimitiveDeserializerFactory.INSTANCE);
+        register(EnumAdapterFactory.INSTANCE);
         register(CollectionAdapterFactory.INSTANCE);
         register(MapAdapterFactory.INSTANCE);
     }

src/main/java/de/bluecolored/bluenbt/adapter/EnumAdapterFactory.java

@@ -0,0 +1,61 @@
+package de.bluecolored.bluenbt.adapter;
+
+import de.bluecolored.bluenbt.*;
+
+import java.io.IOException;
+import java.util.Optional;
+
+public class EnumAdapterFactory implements TypeAdapterFactory {
+
+    public static final EnumAdapterFactory INSTANCE = new EnumAdapterFactory();
+
+    @Override
+    @SuppressWarnings({"unchecked", "rawtypes"})
+    public <T> Optional<? extends TypeAdapter<T>> create(TypeToken<T> type, BlueNBT blueNBT) {
+        Class<? super T> rawType = type.getRawType();
+
+        if (rawType.isEnum())
+            return Optional.of((TypeAdapter<T>) new EnumAdapter(rawType));
+
+        return Optional.empty();
+    }
+
+    static class EnumAdapter<E extends Enum<E>> implements TypeAdapter<E> {
+
+        private final Class<E> enumType;
+        private final E[] universe;
+
+        public EnumAdapter(Class<E> enumType) {
+            this.enumType = enumType;
+            this.universe = enumType.getEnumConstants();
+        }
+
+        @Override
+        public void write(E value, NBTWriter writer) throws IOException {
+            writer.value(value.name());
+        }
+
+        @Override
+        public TagType type() {
+            return TagType.STRING;
+        }
+
+        @Override
+        public E read(NBTReader reader) throws IOException {
+            try {
+                return switch (reader.peek()) {
+                    case STRING -> Enum.valueOf(enumType, reader.nextString());
+                    case LONG -> universe[(int) reader.nextLong()];
+                    case INT -> universe[reader.nextInt()];
+                    case SHORT -> universe[reader.nextShort()];
+                    case BYTE -> universe[reader.nextByte()];
+                    default -> throw new IOException("Can't convert type %s into enum-type %s at %s".formatted(reader.peek(), enumType, reader.path()));
+                };
+            } catch (ArrayIndexOutOfBoundsException | IllegalArgumentException e) {
+                throw new IOException("Invalid value for enum type %s at %s".formatted(enumType, reader.path()));
+            }
+        }
+
+    }
+
+}

src/test/java/de/bluecolored/bluenbt/BlueNBTTest.java

@@ -74,7 +74,7 @@ public void testBlueNBT2() throws IOException {
 
             PlayerData playerData = blueNBT.read(new GZIPInputStream(in), PlayerData.class);
 
-            assertEquals(1, playerData.gameMode);
+            assertEquals(GameMode.CREATIVE, playerData.gameMode);
             assertEquals(-7630795211891119996L, playerData.worldUUIDLeast);
             assertEquals(-192242363273884439L, playerData.worldUUIDMost);
             assertEquals(3, playerData.position.length);
@@ -213,11 +213,18 @@ private enum TestEnum {
         ABC
     }
 
+    private enum GameMode {
+        SURVIVAL,
+        CREATIVE,
+        ADVENTURE,
+        SPECTATOR
+    }
+
     @SuppressWarnings({"unused", "MismatchedReadAndWriteOfArray"})
     private static class PlayerData {
 
         @NBTName("playerGameType")
-        private int gameMode;
+        private GameMode gameMode;
 
         @NBTName("Pos")
         private double[] position;