#1266: Add support for virtual entities

By: Jishuna <joshl5324@gmail.com>

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java

@@ -24,6 +24,7 @@ import net.minecraft.world.entity.EntityFlying;
 import net.minecraft.world.entity.EntityLightning;
 import net.minecraft.world.entity.EntityLiving;
 import net.minecraft.world.entity.EntityTameableAnimal;
+import net.minecraft.world.entity.EntityTypes;
 import net.minecraft.world.entity.GlowSquid;
 import net.minecraft.world.entity.Interaction;
 import net.minecraft.world.entity.Marker;
@@ -164,6 +165,7 @@ import net.minecraft.world.entity.vehicle.EntityMinecartTNT;
 import net.minecraft.world.phys.AxisAlignedBB;
 import org.bukkit.EntityEffect;
 import org.bukkit.Location;
+import org.bukkit.Registry;
 import org.bukkit.Server;
 import org.bukkit.Sound;
 import org.bukkit.World;
@@ -177,8 +179,10 @@ import org.bukkit.craftbukkit.persistence.CraftPersistentDataContainer;
 import org.bukkit.craftbukkit.persistence.CraftPersistentDataTypeRegistry;
 import org.bukkit.craftbukkit.util.CraftChatMessage;
 import org.bukkit.craftbukkit.util.CraftLocation;
+import org.bukkit.craftbukkit.util.CraftNamespacedKey;
 import org.bukkit.craftbukkit.util.CraftSpawnCategory;
 import org.bukkit.craftbukkit.util.CraftVector;
+import org.bukkit.entity.EntitySnapshot;
 import org.bukkit.entity.EntityType;
 import org.bukkit.entity.Player;
 import org.bukkit.entity.Pose;
@@ -641,7 +645,7 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
 
     @Override
     public boolean isValid() {
-        return entity.isAlive() && entity.valid && entity.isChunkLoaded();
+        return entity.isAlive() && entity.valid && entity.isChunkLoaded() && isInWorld();
     }
 
     @Override
@@ -1114,6 +1118,42 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         return CraftSpawnCategory.toBukkit(getHandle().getType().getCategory());
     }
 
+    @Override
+    public boolean isInWorld() {
+        return getHandle().inWorld;
+    }
+
+    @Override
+    public EntitySnapshot createSnapshot() {
+        return CraftEntitySnapshot.create(this);
+    }
+
+    @Override
+    public org.bukkit.entity.Entity copy() {
+        Entity copy = copy(getHandle().level());
+        Preconditions.checkArgument(copy != null, "Error creating new entity.");
+
+        return copy.getBukkitEntity();
+    }
+
+    @Override
+    public org.bukkit.entity.Entity copy(Location location) {
+        Preconditions.checkArgument(location.getWorld() != null, "Location has no world");
+
+        Entity copy = copy(((CraftWorld) location.getWorld()).getHandle());
+        Preconditions.checkArgument(copy != null, "Error creating new entity.");
+
+        copy.setPos(location.getX(), location.getY(), location.getZ());
+        return location.getWorld().addEntity(copy.getBukkitEntity());
+    }
+
+    private Entity copy(net.minecraft.world.level.World level) {
+        NBTTagCompound compoundTag = new NBTTagCompound();
+        getHandle().saveAsPassenger(compoundTag, false);
+
+        return EntityTypes.loadEntityRecursive(compoundTag, level, java.util.function.Function.identity());
+    }
+
     public void storeBukkitValues(NBTTagCompound c) {
         if (!this.persistentDataContainer.isEmpty()) {
             c.put("BukkitValues", this.persistentDataContainer.toTagCompound());

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftEntitySnapshot.java

@@ -0,0 +1,83 @@
+package org.bukkit.craftbukkit.entity;
+
+import com.google.common.base.Preconditions;
+import java.util.function.Function;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.world.entity.EntityTypes;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.EntitySnapshot;
+import org.bukkit.entity.EntityType;
+
+public class CraftEntitySnapshot implements EntitySnapshot {
+    private final NBTTagCompound data;
+    private final EntityType type;
+
+    private CraftEntitySnapshot(NBTTagCompound data, EntityType type) {
+        this.data = data;
+        this.type = type;
+    }
+
+    @Override
+    public EntityType getEntityType() {
+        return type;
+    }
+
+    @Override
+    public Entity createEntity(World world) {
+        net.minecraft.world.entity.Entity internal = createInternal(world);
+
+        return internal.getBukkitEntity();
+    }
+
+    @Override
+    public Entity createEntity(Location location) {
+        Preconditions.checkArgument(location.getWorld() != null, "Location has no world");
+
+        net.minecraft.world.entity.Entity internal = createInternal(location.getWorld());
+
+        internal.setPos(location.getX(), location.getY(), location.getZ());
+        return location.getWorld().addEntity(internal.getBukkitEntity());
+    }
+
+    private net.minecraft.world.entity.Entity createInternal(World world) {
+        net.minecraft.world.level.World nms = ((CraftWorld) world).getHandle();
+        net.minecraft.world.entity.Entity internal = EntityTypes.loadEntityRecursive(data, nms, Function.identity());
+        if (internal == null) { // Try creating by type
+            internal = CraftEntityType.bukkitToMinecraft(type).create(nms);
+        }
+
+        Preconditions.checkArgument(internal != null, "Error creating new entity."); // This should only fail if the stored NBTTagCompound is malformed.
+        internal.load(data);
+
+        return internal;
+    }
+
+    public NBTTagCompound getData() {
+        return data;
+    }
+
+    public static CraftEntitySnapshot create(CraftEntity entity) {
+        NBTTagCompound tag = new NBTTagCompound();
+        if (!entity.getHandle().saveAsPassenger(tag, false)) {
+            return null;
+        }
+
+        return new CraftEntitySnapshot(tag, entity.getType());
+    }
+
+    public static CraftEntitySnapshot create(NBTTagCompound tag, EntityType type) {
+        if (tag == null || tag.isEmpty() || type == null) {
+            return null;
+        }
+
+        return new CraftEntitySnapshot(tag, type);
+    }
+
+    public static CraftEntitySnapshot create(NBTTagCompound tag) {
+        EntityType type = EntityTypes.by(tag).map(CraftEntityType::minecraftToBukkit).orElse(null);
+        return create(tag, type);
+    }
+}

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftHumanEntity.java

@@ -38,6 +38,7 @@ import org.bukkit.Material;
 import org.bukkit.NamespacedKey;
 import org.bukkit.block.Block;
 import org.bukkit.craftbukkit.CraftServer;
+import org.bukkit.craftbukkit.CraftWorld;
 import org.bukkit.craftbukkit.entity.memory.CraftMemoryMapper;
 import org.bukkit.craftbukkit.event.CraftEventFactory;
 import org.bukkit.craftbukkit.inventory.CraftContainer;
@@ -684,4 +685,14 @@ public class CraftHumanEntity extends CraftLivingEntity implements HumanEntity {
         boolean success = getHandle().level().addFreshEntity(fireworks, SpawnReason.CUSTOM);
         return success ? (Firework) fireworks.getBukkitEntity() : null;
     }
+
+    @Override
+    public org.bukkit.entity.Entity copy() {
+        throw new UnsupportedOperationException("Cannot copy human entities");
+    }
+
+    @Override
+    public org.bukkit.entity.Entity copy(Location location) {
+        throw new UnsupportedOperationException("Cannot copy human entities");
+    }
 }