CustomEntityType.java

package me.greenadine.scarecrow.nms;

import java.lang.reflect.Field;
import java.util.List;
import java.util.Map;

import org.bukkit.entity.EntityType;

import net.minecraft.server.v1_12_R1.BiomeBase;
import net.minecraft.server.v1_12_R1.BiomeBase.BiomeMeta;
import net.minecraft.server.v1_12_R1.EntityBat;
import net.minecraft.server.v1_12_R1.EntityChicken;
import net.minecraft.server.v1_12_R1.EntityCow;
import net.minecraft.server.v1_12_R1.EntityHorse;
import net.minecraft.server.v1_12_R1.EntityHorseDonkey;
import net.minecraft.server.v1_12_R1.EntityHorseMule;
import net.minecraft.server.v1_12_R1.EntityHorseSkeleton;
import net.minecraft.server.v1_12_R1.EntityInsentient;
import net.minecraft.server.v1_12_R1.EntityLlama;
import net.minecraft.server.v1_12_R1.EntityMushroomCow;
import net.minecraft.server.v1_12_R1.EntityOcelot;
import net.minecraft.server.v1_12_R1.EntityParrot;
import net.minecraft.server.v1_12_R1.EntityPig;
import net.minecraft.server.v1_12_R1.EntityRabbit;
import net.minecraft.server.v1_12_R1.EntitySheep;
import net.minecraft.server.v1_12_R1.EntitySquid;
import net.minecraft.server.v1_12_R1.EntityTypes;
import net.minecraft.server.v1_12_R1.EntityVillager;

public enum CustomEntityType {

    BAT("Bat", 65, EntityType.BAT, EntityBat.class, CustomEntityBat.class),
    CHICKEN("Chicken", 93, EntityType.CHICKEN, EntityChicken.class, CustomEntityBat.class),
    COW("Cow", 92, EntityType.COW, EntityCow.class, CustomEntityBat.class),
    MUSHROOM_COW("Mooshroom", 96, EntityType.MUSHROOM_COW, EntityMushroomCow.class, CustomEntityBat.class),
    OCELOT("Ocelot", 98, EntityType.OCELOT, EntityOcelot.class, CustomEntityBat.class),
    PARROT("Parrot", 105, EntityType.PARROT, EntityParrot.class, CustomEntityBat.class),
    PIG("Pig", 90, EntityType.PIG, EntityPig.class, CustomEntityBat.class),
    RABBIT("Rabbit", 101, EntityType.RABBIT, EntityRabbit.class, CustomEntityBat.class),
    SHEEP("Sheep", 91, EntityType.SHEEP, EntitySheep.class, CustomEntityBat.class),
    SQUID("Squid", 94, EntityType.SQUID, EntitySquid.class, CustomEntityBat.class),
    HORSE("Horse", 100, EntityType.HORSE, EntityHorse.class, CustomEntityBat.class),
    HORSE_SKELETON("Skeleton Horse", 28, EntityType.SKELETON_HORSE, EntityHorseSkeleton.class, CustomEntityBat.class),
    HORSE_DONKEY("Donkey", 31, EntityType.DONKEY, EntityHorseDonkey.class, CustomEntityBat.class),
    HORSE_MULE("MULE", 32, EntityType.MULE, EntityHorseMule.class, CustomEntityBat.class),
    LLAMA("Llama", 103, EntityType.LLAMA, EntityLlama.class, CustomEntityBat.class),
    VILLAGER("Villager", 120, EntityType.VILLAGER, EntityVillager.class, CustomEntityBat.class);


    private String name;
    private int id;
    private EntityType entityType;
    private Class<? extends EntityInsentient> nmsClass;
    private Class<? extends EntityInsentient> customClass;

    private CustomEntityType(String name, int id, EntityType entityType, Class<? extends EntityInsentient> nmsClass, Class<? extends EntityInsentient> customClass)
    {
        this.name = name;
        this.id = id;
        this.entityType = entityType;
        this.nmsClass = nmsClass;
        this.customClass = customClass;
    }

    public String getName()
    {
        return name;
    }

    public int getID()
    {
        return id;
    }

    public EntityType getEntityType()
    {
        return entityType;
    }

    public Class<? extends EntityInsentient> getNMSClass()
    {
        return nmsClass;
    }

    public Class<? extends EntityInsentient> getCustomClass()
    {
        return customClass;
    }

    /**
    * Register our entities.
    */
    public static void registerEntities()
    {
        for (CustomEntityType entity : values())
            a(entity.getCustomClass(), entity.getName(), entity.getID());

        // BiomeBase#biomes became private.
        BiomeBase[] biomes;
        try
        {
            biomes = (BiomeBase[]) getPrivateStatic(BiomeBase.class, "biomes");
        } catch (Exception exc)
        {
            // Unable to fetch.
            return;
        }
        for (BiomeBase biomeBase : biomes)
        {
            if (biomeBase == null)
                break;

            // This changed names from J, K, L and M.
            for (String field : new String[] { "as", "at", "au", "av" })
            {
                try
                {
                    Field list = BiomeBase.class.getDeclaredField(field);
                    list.setAccessible(true);
                    @SuppressWarnings("unchecked")
                    List<BiomeMeta> mobList = (List<BiomeMeta>) list.get(biomeBase);

                    // Write in our custom class.
                    for (BiomeMeta meta : mobList)
                        for (CustomEntityType entity : values())
                            if (entity.getNMSClass().equals(meta.b))
                                meta.b = entity.getCustomClass();
                } catch (Exception e)
                {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
    * Unregister our entities to prevent memory leaks. Call on disable.
    */
    @SuppressWarnings("rawtypes")
    public static void unregisterEntities() {
        for (CustomEntityType entity : values()) {
            // Remove our class references.
            try {
                ((Map) getPrivateStatic(EntityTypes.class, "d")).remove(entity.getCustomClass());
            } catch (Exception e) {
                e.printStackTrace();
            }

            try {
                ((Map) getPrivateStatic(EntityTypes.class, "f")).remove(entity.getCustomClass());
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        for (CustomEntityType entity : values())
            try {
                // Unregister each entity by writing the NMS back in place of the custom class.
                a(entity.getNMSClass(), entity.getName(), entity.getID());
            } catch (Exception e) {
                e.printStackTrace();
            }

            // Biomes#biomes was made private so use reflection to get it.
            BiomeBase[] biomes;
            try {
                biomes = (BiomeBase[]) getPrivateStatic(BiomeBase.class, "biomes");
            } catch (Exception exc) {
                // Unable to fetch.
                return;
            }
            for (BiomeBase biomeBase : biomes) {
                if (biomeBase == null)
                    break;

                // The list fields changed names but update the meta regardless.
                for (String field : new String[] { "as", "at", "au", "av" })
                    try {
                        Field list = BiomeBase.class.getDeclaredField(field);
                        list.setAccessible(true);
                        @SuppressWarnings("unchecked")
                        List<BiomeMeta> mobList = (List<BiomeMeta>) list.get(biomeBase);

                        // Make sure the NMS class is written back over our custom class.
                        for (BiomeMeta meta : mobList)
                            for (CustomEntityType entity : values())
                                if (entity.getCustomClass().equals(meta.b))
                                    meta.b = entity.getNMSClass();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
            }
    }

    /**
    * A convenience method.
    * @param clazz The class.
    * @param f The string representation of the private static field.
    * @return The object found
    * @throws Exception if unable to get the object.
    */
    @SuppressWarnings("rawtypes")
    private static Object getPrivateStatic(Class clazz, String f) throws Exception {
        Field field = clazz.getDeclaredField(f);
        field.setAccessible(true);
        return field.get(null);
        }

    /*
    * Since 1.7.2 added a check in their entity registration, simply bypass it and write to the maps ourself.
    */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    private static void a(Class paramClass, String paramString, int paramInt) {
        try {
            ((Map) getPrivateStatic(EntityTypes.class, "c")).put(paramString, paramClass);
            ((Map) getPrivateStatic(EntityTypes.class, "d")).put(paramClass, paramString);
            ((Map) getPrivateStatic(EntityTypes.class, "e")).put(Integer.valueOf(paramInt), paramClass);
            ((Map) getPrivateStatic(EntityTypes.class, "f")).put(paramClass, Integer.valueOf(paramInt));
            ((Map) getPrivateStatic(EntityTypes.class, "g")).put(paramString, Integer.valueOf(paramInt));
        } catch (Exception exc) {
            // Unable to register the new class.
        }
    }
}