From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Mariell Hoversholm <proximyst@proximyst.com>
Date: Sun, 24 Oct 2021 16:20:31 -0400
Subject: [PATCH] Add Raw Byte Entity Serialization

== AT ==
public net.minecraft.world.entity.Entity setLevel(Lnet/minecraft/world/level/Level;)V

diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index dd353bad7ddf7c1e4bbc37ed3724d73696f7b8a7..cdb69f4d5d49a2459671fa86dc39d60fdfa62489 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -2106,6 +2106,15 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
         }
     }
 
+    // Paper start - Entity serialization api
+    public boolean serializeEntity(CompoundTag compound) {
+        List<Entity> pass = new java.util.ArrayList<>(this.getPassengers());
+        this.passengers = ImmutableList.of();
+        boolean result = save(compound);
+        this.passengers = ImmutableList.copyOf(pass);
+        return result;
+    }
+    // Paper end - Entity serialization api
     public boolean save(CompoundTag nbt) {
         return this.isPassenger() ? false : this.saveAsPassenger(nbt);
     }
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
index 9edcdc71b28cf08e42fbe44723ba540e8d4f7808..a61638bc8200f6aa25d9c3254aea6c0cd38bcbf1 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
@@ -1068,6 +1068,18 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
     }
     // Paper end - tracked players API
 
+    // Paper start - raw entity serialization API
+    @Override
+    public boolean spawnAt(Location location, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason) {
+        Preconditions.checkNotNull(location, "location cannot be null");
+        Preconditions.checkNotNull(reason, "reason cannot be null");
+        this.entity.setLevel(((CraftWorld) location.getWorld()).getHandle());
+        this.entity.setPos(location.getX(), location.getY(), location.getZ());
+        this.entity.setRot(location.getYaw(), location.getPitch());
+        return !this.entity.valid && this.entity.level().addFreshEntity(this.entity, reason);
+    }
+    // Paper end - raw entity serialization API
+
     // Paper start - missing entity api
     @Override
     public boolean isInvisible() {  // Paper - moved up from LivingEntity
diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
index 03ac06c4bd89e6da2272c3ff109a1b2d3454efd2..64327d5dd0e1ec3f5ad411ee692923a340d6174f 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
@@ -509,7 +509,33 @@ public final class CraftMagicNumbers implements UnsafeValues {
         return CraftItemStack.asCraftMirror(net.minecraft.world.item.ItemStack.parse(MinecraftServer.getServer().registryAccess(), compound).orElseThrow());
     }
 
-    private byte[] serializeNbtToBytes(CompoundTag compound) {
+    @Override
+    public byte[] serializeEntity(org.bukkit.entity.Entity entity) {
+        Preconditions.checkNotNull(entity, "null cannot be serialized");
+        Preconditions.checkArgument(entity instanceof org.bukkit.craftbukkit.entity.CraftEntity, "only CraftEntities can be serialized");
+
+        net.minecraft.nbt.CompoundTag compound = new net.minecraft.nbt.CompoundTag();
+        ((org.bukkit.craftbukkit.entity.CraftEntity) entity).getHandle().serializeEntity(compound);
+        return serializeNbtToBytes(compound);
+    }
+
+    @Override
+    public org.bukkit.entity.Entity deserializeEntity(byte[] data, org.bukkit.World world, boolean preserveUUID) {
+        Preconditions.checkNotNull(data, "null cannot be deserialized");
+        Preconditions.checkArgument(data.length > 0, "cannot deserialize nothing");
+
+        net.minecraft.nbt.CompoundTag compound = deserializeNbtFromBytes(data);
+        int dataVersion = compound.getInt("DataVersion");
+        compound = (net.minecraft.nbt.CompoundTag) MinecraftServer.getServer().fixerUpper.update(References.ENTITY, new Dynamic<>(NbtOps.INSTANCE, compound), dataVersion, this.getDataVersion()).getValue();
+        if (!preserveUUID) {
+            // Generate a new UUID so we don't have to worry about deserializing the same entity twice
+            compound.remove("UUID");
+        }
+        return net.minecraft.world.entity.EntityType.create(compound, ((org.bukkit.craftbukkit.CraftWorld) world).getHandle())
+            .orElseThrow(() -> new IllegalArgumentException("An ID was not found for the data. Did you downgrade?")).getBukkitEntity();
+    }
+
+    private byte[] serializeNbtToBytes(net.minecraft.nbt.CompoundTag compound) {
         compound.putInt("DataVersion", getDataVersion());
         java.io.ByteArrayOutputStream outputStream = new java.io.ByteArrayOutputStream();
         try {
