Add modifier for EntityTypes

Fixes #710

src/main/java/com/comphenix/protocol/events/PacketContainer.java

@@ -58,6 +58,7 @@ import org.bukkit.Sound;
 import org.bukkit.World;
 import org.bukkit.WorldType;
 import org.bukkit.entity.Entity;
+import org.bukkit.entity.EntityType;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.potion.PotionEffectType;
 import org.bukkit.util.Vector;
@@ -436,6 +437,16 @@ public class PacketContainer implements Serializable {
 		Preconditions.checkNotNull(event, "event cannot be NULL.");
 		return getEntityModifier(event.getPlayer().getWorld());
 	}
+
+	/**
+	 * Retrieves a read/write structure for entity types
+	 * @return A modifier for an EntityType.
+	 */
+	public StructureModifier<EntityType> getEntityTypeModifier() {
+		return structureModifier.withType(
+				MinecraftReflection.getMinecraftClass("EntityTypes"),
+				BukkitConverters.getEntityTypeConverter());
+	}
 	
 	/**
 	 * Retrieves a read/write structure for chunk positions.

src/main/java/com/comphenix/protocol/wrappers/BukkitConverters.java

@@ -49,12 +49,15 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
 
+import net.minecraft.server.v1_14_R1.EntityTypes;
+
 import org.bukkit.Material;
 import org.bukkit.Sound;
 import org.bukkit.World;
 import org.bukkit.WorldType;
 import org.bukkit.advancement.Advancement;
 import org.bukkit.entity.Entity;
+import org.bukkit.entity.EntityType;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.potion.PotionEffect;
 import org.bukkit.potion.PotionEffectType;
@@ -655,6 +658,54 @@ public class BukkitConverters {
 			}
 		};
 	}
+
+	private static MethodAccessor getEntityTypeName;
+	private static MethodAccessor entityTypeFromName;
+
+	public static EquivalentConverter<EntityType> getEntityTypeConverter() {
+		return ignoreNull(new EquivalentConverter<EntityType>() {
+			@Override
+			public Object getGeneric(EntityType specific) {
+				if (entityTypeFromName == null) {
+					Class<?> entityTypesClass = MinecraftReflection.getMinecraftClass("EntityTypes");
+					entityTypeFromName = Accessors.getMethodAccessor(
+							FuzzyReflection
+									.fromClass(entityTypesClass, false)
+									.getMethod(FuzzyMethodContract
+											           .newBuilder()
+											           .returnDerivedOf(Optional.class)
+											           .parameterExactArray(new Class<?>[]{ String.class })
+											           .build()));
+				}
+
+				Optional<?> opt = (Optional<?>) entityTypeFromName.invoke(null, specific.getName());
+				return opt.orElse(null);
+			}
+
+			@Override
+			public EntityType getSpecific(Object generic) {
+				if (getEntityTypeName == null) {
+					Class<?> entityTypesClass = MinecraftReflection.getMinecraftClass("EntityTypes");
+					getEntityTypeName = Accessors.getMethodAccessor(
+							FuzzyReflection
+									.fromClass(entityTypesClass, false)
+									.getMethod(FuzzyMethodContract
+											           .newBuilder()
+											           .returnTypeExact(MinecraftReflection.getMinecraftKeyClass())
+											           .parameterExactArray(new Class<?>[]{ entityTypesClass })
+											           .build()));
+				}
+
+				MinecraftKey key = MinecraftKey.fromHandle(getEntityTypeName.invoke(null, generic));
+				return EntityType.fromName(key.getKey());
+			}
+
+			@Override
+			public Class<EntityType> getSpecificType() {
+				return EntityType.class;
+			}
+		});
+	}
 	
 	/**
 	 * Retrieve the converter used to convert NMS ItemStacks to Bukkit's ItemStack.

src/test/java/com/comphenix/protocol/events/PacketContainerTest.java

@@ -46,6 +46,7 @@ import org.bukkit.ChatColor;
 import org.bukkit.Material;
 import org.bukkit.Sound;
 import org.bukkit.WorldType;
+import org.bukkit.entity.EntityType;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.inventory.meta.ItemMeta;
 import org.bukkit.potion.PotionEffect;
@@ -289,6 +290,14 @@ public class PacketContainerTest {
 	//  @Test
 	//  public void testGetPositionModifier() { }
 
+	@Test
+	public void testEntityTypeModifier() {
+		PacketContainer packet = new PacketContainer(PacketType.Play.Server.SPAWN_ENTITY);
+
+		packet.getEntityTypeModifier().write(0, EntityType.ARROW);
+		assertEquals(packet.getEntityTypeModifier().read(0), EntityType.ARROW);
+	}
+
 	@Test
 	public void testGetPositionCollectionModifier() {
 		PacketContainer explosionPacket = new PacketContainer(PacketType.Play.Server.EXPLOSION);