6 files changed, 813 insertions, 1 deletions
diff --git a/src/server/CMakeLists.txt b/src/server/CMakeLists.txt
index e964c69ff..9fa5ed9fa 100644
--- a/src/server/CMakeLists.txt
+++ b/src/server/CMakeLists.txt
@@ -1,4 +1,6 @@
 set(server_SRCS
 	${CMAKE_CURRENT_SOURCE_DIR}/activeobjectmgr.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/mods.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/serveractiveobject.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/unit_sao.cpp
 	PARENT_SCOPE)
diff --git a/src/server/activeobjectmgr.h b/src/server/activeobjectmgr.h
index a502ac6ed..5fea1bea6 100644
--- a/src/server/activeobjectmgr.h
+++ b/src/server/activeobjectmgr.h
@@ -22,7 +22,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include <functional>
 #include <vector>
 #include "../activeobjectmgr.h"
-#include "serverobject.h"
+#include "serveractiveobject.h"
 
 namespace server
 {
diff --git a/src/server/serveractiveobject.cpp b/src/server/serveractiveobject.cpp
new file mode 100644
index 000000000..3aa78c7d5
--- /dev/null
+++ b/src/server/serveractiveobject.cpp
@@ -0,0 +1,114 @@
+/*
+Minetest
+Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "serveractiveobject.h"
+#include <fstream>
+#include "inventory.h"
+#include "constants.h" // BS
+#include "log.h"
+
+ServerActiveObject::ServerActiveObject(ServerEnvironment *env, v3f pos):
+	ActiveObject(0),
+	m_env(env),
+	m_base_position(pos)
+{
+}
+
+ServerActiveObject* ServerActiveObject::create(ActiveObjectType type,
+		ServerEnvironment *env, u16 id, v3f pos,
+		const std::string &data)
+{
+	// Find factory function
+	std::map<u16, Factory>::iterator n;
+	n = m_types.find(type);
+	if(n == m_types.end()) {
+		// These are 0.3 entity types, return without error.
+		if (ACTIVEOBJECT_TYPE_ITEM <= type && type <= ACTIVEOBJECT_TYPE_MOBV2) {
+			return NULL;
+		}
+
+		// If factory is not found, just return.
+		warningstream<<"ServerActiveObject: No factory for type="
+				<<type<<std::endl;
+		return NULL;
+	}
+
+	Factory f = n->second;
+	ServerActiveObject *object = (*f)(env, pos, data);
+	return object;
+}
+
+void ServerActiveObject::registerType(u16 type, Factory f)
+{
+	std::map<u16, Factory>::iterator n;
+	n = m_types.find(type);
+	if(n != m_types.end())
+		return;
+	m_types[type] = f;
+}
+
+float ServerActiveObject::getMinimumSavedMovement()
+{
+	return 2.0*BS;
+}
+
+ItemStack ServerActiveObject::getWieldedItem(ItemStack *selected, ItemStack *hand) const
+{
+	*selected = ItemStack();
+	if (hand)
+		*hand = ItemStack();
+
+	return ItemStack();
+}
+
+bool ServerActiveObject::setWieldedItem(const ItemStack &item)
+{
+	return false;
+}
+
+std::string ServerActiveObject::generateUpdateInfantCommand(u16 infant_id, u16 protocol_version)
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_SPAWN_INFANT);
+	// parameters
+	writeU16(os, infant_id);
+	writeU8(os, getSendType());
+	os << serializeLongString(getClientInitializationData(protocol_version));
+	return os.str();
+}
+
+std::string ServerActiveObject::generateUpdateNametagAttributesCommand(const video::SColor &color) const
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_UPDATE_NAMETAG_ATTRIBUTES);
+	// parameters
+	writeU8(os, 1); // version for forward compatibility
+	writeARGB8(os, color);
+	return os.str();
+}
+
+void ServerActiveObject::dumpAOMessagesToQueue(std::queue<ActiveObjectMessage> &queue)
+{
+	while (!m_messages_out.empty()) {
+		queue.push(m_messages_out.front());
+		m_messages_out.pop();
+	}
+}
+\ No newline at end of file
diff --git a/src/server/serveractiveobject.h b/src/server/serveractiveobject.h
new file mode 100644
index 000000000..2e013a6b6
--- /dev/null
+++ b/src/server/serveractiveobject.h
@@ -0,0 +1,265 @@
+/*
+Minetest
+Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+
+#include <unordered_set>
+#include "irrlichttypes_bloated.h"
+#include "activeobject.h"
+#include "inventorymanager.h"
+#include "itemgroup.h"
+#include "util/container.h"
+
+/*
+
+Some planning
+-------------
+
+* Server environment adds an active object, which gets the id 1
+* The active object list is scanned for each client once in a while,
+  and it finds out what objects have been added that are not known
+  by the client yet. This scan is initiated by the Server class and
+  the result ends up directly to the server.
+* A network packet is created with the info and sent to the client.
+* Environment converts objects to static data and static data to
+  objects, based on how close players are to them.
+
+*/
+
+class ServerEnvironment;
+struct ItemStack;
+struct ToolCapabilities;
+struct ObjectProperties;
+struct PlayerHPChangeReason;
+
+class ServerActiveObject : public ActiveObject
+{
+public:
+	/*
+		NOTE: m_env can be NULL, but step() isn't called if it is.
+		Prototypes are used that way.
+	*/
+	ServerActiveObject(ServerEnvironment *env, v3f pos);
+	virtual ~ServerActiveObject() = default;
+
+	virtual ActiveObjectType getSendType() const
+	{ return getType(); }
+
+	// Called after id has been set and has been inserted in environment
+	virtual void addedToEnvironment(u32 dtime_s){};
+	// Called before removing from environment
+	virtual void removingFromEnvironment(){};
+	// Returns true if object's deletion is the job of the
+	// environment
+	virtual bool environmentDeletes() const
+	{ return true; }
+
+	// Create a certain type of ServerActiveObject
+	static ServerActiveObject* create(ActiveObjectType type,
+			ServerEnvironment *env, u16 id, v3f pos,
+			const std::string &data);
+
+	/*
+		Some simple getters/setters
+	*/
+	v3f getBasePosition() const { return m_base_position; }
+	void setBasePosition(v3f pos){ m_base_position = pos; }
+	ServerEnvironment* getEnv(){ return m_env; }
+
+	/*
+		Some more dynamic interface
+	*/
+
+	virtual void setPos(const v3f &pos)
+		{ setBasePosition(pos); }
+	// continuous: if true, object does not stop immediately at pos
+	virtual void moveTo(v3f pos, bool continuous)
+		{ setBasePosition(pos); }
+	// If object has moved less than this and data has not changed,
+	// saving to disk may be omitted
+	virtual float getMinimumSavedMovement();
+
+	virtual std::string getDescription(){return "SAO";}
+
+	/*
+		Step object in time.
+		Messages added to messages are sent to client over network.
+
+		send_recommended:
+			True at around 5-10 times a second, same for all objects.
+			This is used to let objects send most of the data at the
+			same time so that the data can be combined in a single
+			packet.
+	*/
+	virtual void step(float dtime, bool send_recommended){}
+
+	/*
+		The return value of this is passed to the client-side object
+		when it is created
+	*/
+	virtual std::string getClientInitializationData(u16 protocol_version) {return "";}
+
+	/*
+		The return value of this is passed to the server-side object
+		when it is created (converted from static to active - actually
+		the data is the static form)
+	*/
+	virtual void getStaticData(std::string *result) const
+	{
+		assert(isStaticAllowed());
+		*result = "";
+	}
+	/*
+		Return false in here to never save and instead remove object
+		on unload. getStaticData() will not be called in that case.
+	*/
+	virtual bool isStaticAllowed() const
+	{return true;}
+
+	// Returns tool wear
+	virtual u16 punch(v3f dir,
+			const ToolCapabilities *toolcap = nullptr,
+			ServerActiveObject *puncher = nullptr,
+			float time_from_last_punch = 1000000.0f)
+	{ return 0; }
+	virtual void rightClick(ServerActiveObject *clicker)
+	{}
+	virtual void setHP(s32 hp, const PlayerHPChangeReason &reason)
+	{}
+	virtual u16 getHP() const
+	{ return 0; }
+
+	virtual void setArmorGroups(const ItemGroupList &armor_groups)
+	{}
+	virtual const ItemGroupList &getArmorGroups() const
+	{ static ItemGroupList rv; return rv; }
+	virtual void setPhysicsOverride(float physics_override_speed, float physics_override_jump, float physics_override_gravity)
+	{}
+	virtual void setAnimation(v2f frames, float frame_speed, float frame_blend, bool frame_loop)
+	{}
+	virtual void getAnimation(v2f *frames, float *frame_speed, float *frame_blend, bool *frame_loop)
+	{}
+	virtual void setAnimationSpeed(float frame_speed)
+	{}
+	virtual void setBonePosition(const std::string &bone, v3f position, v3f rotation)
+	{}
+	virtual void getBonePosition(const std::string &bone, v3f *position, v3f *lotation)
+	{}
+	virtual const std::unordered_set<int> &getAttachmentChildIds() const
+	{ static std::unordered_set<int> rv; return rv; }
+	virtual ServerActiveObject *getParent() const { return nullptr; }
+	virtual ObjectProperties* accessObjectProperties()
+	{ return NULL; }
+	virtual void notifyObjectPropertiesModified()
+	{}
+
+	// Inventory and wielded item
+	virtual Inventory *getInventory() const
+	{ return NULL; }
+	virtual InventoryLocation getInventoryLocation() const
+	{ return InventoryLocation(); }
+	virtual void setInventoryModified()
+	{}
+	virtual std::string getWieldList() const
+	{ return ""; }
+	virtual u16 getWieldIndex() const
+	{ return 0; }
+	virtual ItemStack getWieldedItem(ItemStack *selected,
+			ItemStack *hand = nullptr) const;
+	virtual bool setWieldedItem(const ItemStack &item);
+	inline void attachParticleSpawner(u32 id)
+	{
+		m_attached_particle_spawners.insert(id);
+	}
+	inline void detachParticleSpawner(u32 id)
+	{
+		m_attached_particle_spawners.erase(id);
+	}
+
+	std::string generateUpdateInfantCommand(u16 infant_id, u16 protocol_version);
+	std::string generateUpdateNametagAttributesCommand(const video::SColor &color) const;
+
+	void dumpAOMessagesToQueue(std::queue<ActiveObjectMessage> &queue);
+
+	/*
+		Number of players which know about this object. Object won't be
+		deleted until this is 0 to keep the id preserved for the right
+		object.
+	*/
+	u16 m_known_by_count = 0;
+
+	/*
+		- Whether this object is to be removed when nobody knows about
+		  it anymore.
+		- Removal is delayed to preserve the id for the time during which
+		  it could be confused to some other object by some client.
+		- This is usually set to true by the step() method when the object wants
+		  to be deleted but can be set by anything else too.
+	*/
+	bool m_pending_removal = false;
+
+	/*
+		Same purpose as m_pending_removal but for deactivation.
+		deactvation = save static data in block, remove active object
+
+		If this is set alongside with m_pending_removal, removal takes
+		priority.
+	*/
+	bool m_pending_deactivation = false;
+
+	/*
+		A getter that unifies the above to answer the question:
+		"Can the environment still interact with this object?"
+	*/
+	inline bool isGone() const
+	{ return m_pending_removal || m_pending_deactivation; }
+
+	/*
+		Whether the object's static data has been stored to a block
+	*/
+	bool m_static_exists = false;
+	/*
+		The block from which the object was loaded from, and in which
+		a copy of the static data resides.
+	*/
+	v3s16 m_static_block = v3s16(1337,1337,1337);
+
+protected:
+	virtual void onAttach(int parent_id) {}
+	virtual void onDetach(int parent_id) {}
+
+	// Used for creating objects based on type
+	typedef ServerActiveObject* (*Factory)
+			(ServerEnvironment *env, v3f pos,
+			const std::string &data);
+	static void registerType(u16 type, Factory f);
+
+	ServerEnvironment *m_env;
+	v3f m_base_position;
+	std::unordered_set<u32> m_attached_particle_spawners;
+
+	/*
+		Queue of messages to be sent to the client
+	*/
+	std::queue<ActiveObjectMessage> m_messages_out;
+
+private:
+	// Used for creating objects based on type
+	static std::map<u16, Factory> m_types;
+};
diff --git a/src/server/unit_sao.cpp b/src/server/unit_sao.cpp
new file mode 100644
index 000000000..66be67522
--- /dev/null
+++ b/src/server/unit_sao.cpp
@@ -0,0 +1,318 @@
+/*
+Minetest
+Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+Copyright (C) 2013-2020 Minetest core developers & community
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "unit_sao.h"
+#include "scripting_server.h"
+#include "serverenvironment.h"
+
+/*
+	UnitSAO
+ */
+
+UnitSAO::UnitSAO(ServerEnvironment *env, v3f pos):
+	ServerActiveObject(env, pos)
+{
+	// Initialize something to armor groups
+	m_armor_groups["fleshy"] = 100;
+}
+
+ServerActiveObject *UnitSAO::getParent() const
+{
+	if (!m_attachment_parent_id)
+		return nullptr;
+	// Check if the parent still exists
+	ServerActiveObject *obj = m_env->getActiveObject(m_attachment_parent_id);
+
+	return obj;
+}
+
+void UnitSAO::setArmorGroups(const ItemGroupList &armor_groups)
+{
+	m_armor_groups = armor_groups;
+	m_armor_groups_sent = false;
+}
+
+const ItemGroupList &UnitSAO::getArmorGroups() const
+{
+	return m_armor_groups;
+}
+
+void UnitSAO::setAnimation(v2f frame_range, float frame_speed, float frame_blend, bool frame_loop)
+{
+	// store these so they can be updated to clients
+	m_animation_range = frame_range;
+	m_animation_speed = frame_speed;
+	m_animation_blend = frame_blend;
+	m_animation_loop = frame_loop;
+	m_animation_sent = false;
+}
+
+void UnitSAO::getAnimation(v2f *frame_range, float *frame_speed, float *frame_blend, bool *frame_loop)
+{
+	*frame_range = m_animation_range;
+	*frame_speed = m_animation_speed;
+	*frame_blend = m_animation_blend;
+	*frame_loop = m_animation_loop;
+}
+
+void UnitSAO::setAnimationSpeed(float frame_speed)
+{
+	m_animation_speed = frame_speed;
+	m_animation_speed_sent = false;
+}
+
+void UnitSAO::setBonePosition(const std::string &bone, v3f position, v3f rotation)
+{
+	// store these so they can be updated to clients
+	m_bone_position[bone] = core::vector2d<v3f>(position, rotation);
+	m_bone_position_sent = false;
+}
+
+void UnitSAO::getBonePosition(const std::string &bone, v3f *position, v3f *rotation)
+{
+	*position = m_bone_position[bone].X;
+	*rotation = m_bone_position[bone].Y;
+}
+
+void UnitSAO::setAttachment(int parent_id, const std::string &bone, v3f position, v3f rotation)
+{
+	// Attachments need to be handled on both the server and client.
+	// If we just attach on the server, we can only copy the position of the parent. Attachments
+	// are still sent to clients at an interval so players might see them lagging, plus we can't
+	// read and attach to skeletal bones.
+	// If we just attach on the client, the server still sees the child at its original location.
+	// This breaks some things so we also give the server the most accurate representation
+	// even if players only see the client changes.
+
+	int old_parent = m_attachment_parent_id;
+	m_attachment_parent_id = parent_id;
+	m_attachment_bone = bone;
+	m_attachment_position = position;
+	m_attachment_rotation = rotation;
+	m_attachment_sent = false;
+
+	if (parent_id != old_parent) {
+		onDetach(old_parent);
+		onAttach(parent_id);
+	}
+}
+
+void UnitSAO::getAttachment(int *parent_id, std::string *bone, v3f *position,
+	v3f *rotation) const
+{
+	*parent_id = m_attachment_parent_id;
+	*bone = m_attachment_bone;
+	*position = m_attachment_position;
+	*rotation = m_attachment_rotation;
+}
+
+void UnitSAO::clearChildAttachments()
+{
+	for (int child_id : m_attachment_child_ids) {
+		// Child can be NULL if it was deleted earlier
+		if (ServerActiveObject *child = m_env->getActiveObject(child_id))
+			child->setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0));
+	}
+	m_attachment_child_ids.clear();
+}
+
+void UnitSAO::clearParentAttachment()
+{
+	ServerActiveObject *parent = nullptr;
+	if (m_attachment_parent_id) {
+		parent = m_env->getActiveObject(m_attachment_parent_id);
+		setAttachment(0, "", m_attachment_position, m_attachment_rotation);
+	} else {
+		setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0));
+	}
+	// Do it
+	if (parent)
+		parent->removeAttachmentChild(m_id);
+}
+
+void UnitSAO::addAttachmentChild(int child_id)
+{
+	m_attachment_child_ids.insert(child_id);
+}
+
+void UnitSAO::removeAttachmentChild(int child_id)
+{
+	m_attachment_child_ids.erase(child_id);
+}
+
+const std::unordered_set<int> &UnitSAO::getAttachmentChildIds() const
+{
+	return m_attachment_child_ids;
+}
+
+void UnitSAO::onAttach(int parent_id)
+{
+	if (!parent_id)
+		return;
+
+	ServerActiveObject *parent = m_env->getActiveObject(parent_id);
+
+	if (!parent || parent->isGone())
+		return; // Do not try to notify soon gone parent
+
+	if (parent->getType() == ACTIVEOBJECT_TYPE_LUAENTITY) {
+		// Call parent's on_attach field
+		m_env->getScriptIface()->luaentity_on_attach_child(parent_id, this);
+	}
+}
+
+void UnitSAO::onDetach(int parent_id)
+{
+	if (!parent_id)
+		return;
+
+	ServerActiveObject *parent = m_env->getActiveObject(parent_id);
+	if (getType() == ACTIVEOBJECT_TYPE_LUAENTITY)
+		m_env->getScriptIface()->luaentity_on_detach(m_id, parent);
+
+	if (!parent || parent->isGone())
+		return; // Do not try to notify soon gone parent
+
+	if (parent->getType() == ACTIVEOBJECT_TYPE_LUAENTITY)
+		m_env->getScriptIface()->luaentity_on_detach_child(parent_id, this);
+}
+
+ObjectProperties* UnitSAO::accessObjectProperties()
+{
+	return &m_prop;
+}
+
+void UnitSAO::notifyObjectPropertiesModified()
+{
+	m_properties_sent = false;
+}
+
+std::string UnitSAO::generateUpdateAttachmentCommand() const
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_ATTACH_TO);
+	// parameters
+	writeS16(os, m_attachment_parent_id);
+	os << serializeString(m_attachment_bone);
+	writeV3F32(os, m_attachment_position);
+	writeV3F32(os, m_attachment_rotation);
+	return os.str();
+}
+
+std::string UnitSAO::generateUpdateBonePositionCommand(const std::string &bone,
+	const v3f &position, const v3f &rotation)
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_SET_BONE_POSITION);
+	// parameters
+	os << serializeString(bone);
+	writeV3F32(os, position);
+	writeV3F32(os, rotation);
+	return os.str();
+}
+
+
+std::string UnitSAO::generateUpdateAnimationSpeedCommand() const
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_SET_ANIMATION_SPEED);
+	// parameters
+	writeF32(os, m_animation_speed);
+	return os.str();
+}
+
+std::string UnitSAO::generateUpdateAnimationCommand() const
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_SET_ANIMATION);
+	// parameters
+	writeV2F32(os, m_animation_range);
+	writeF32(os, m_animation_speed);
+	writeF32(os, m_animation_blend);
+	// these are sent inverted so we get true when the server sends nothing
+	writeU8(os, !m_animation_loop);
+	return os.str();
+}
+
+
+std::string UnitSAO::generateUpdateArmorGroupsCommand() const
+{
+	std::ostringstream os(std::ios::binary);
+	writeU8(os, AO_CMD_UPDATE_ARMOR_GROUPS);
+	writeU16(os, m_armor_groups.size());
+	for (const auto &armor_group : m_armor_groups) {
+		os<<serializeString(armor_group.first);
+		writeS16(os, armor_group.second);
+	}
+	return os.str();
+}
+
+
+std::string UnitSAO::generateUpdatePositionCommand(const v3f &position, const v3f &velocity,
+	const v3f &acceleration, const v3f &rotation, bool do_interpolate, bool is_movement_end,
+	f32 update_interval)
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_UPDATE_POSITION);
+	// pos
+	writeV3F32(os, position);
+	// velocity
+	writeV3F32(os, velocity);
+	// acceleration
+	writeV3F32(os, acceleration);
+	// rotation
+	writeV3F32(os, rotation);
+	// do_interpolate
+	writeU8(os, do_interpolate);
+	// is_end_position (for interpolation)
+	writeU8(os, is_movement_end);
+	// update_interval (for interpolation)
+	writeF32(os, update_interval);
+	return os.str();
+}
+
+
+std::string UnitSAO::generateSetPropertiesCommand(const ObjectProperties &prop) const
+{
+	std::ostringstream os(std::ios::binary);
+	writeU8(os, AO_CMD_SET_PROPERTIES);
+	prop.serialize(os);
+	return os.str();
+}
+
+std::string UnitSAO::generatePunchCommand(u16 result_hp) const
+{
+	std::ostringstream os(std::ios::binary);
+	// command
+	writeU8(os, AO_CMD_PUNCHED);
+	// result_hp
+	writeU16(os, result_hp);
+	return os.str();
+}
+
+void UnitSAO::sendPunchCommand()
+{
+	m_messages_out.emplace(getId(), true, generatePunchCommand(getHP()));
+}
diff --git a/src/server/unit_sao.h b/src/server/unit_sao.h
new file mode 100644
index 000000000..d0e20fb77
--- /dev/null
+++ b/src/server/unit_sao.h
@@ -0,0 +1,113 @@
+/*
+Minetest
+Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+Copyright (C) 2013-2020 Minetest core developers & community
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+
+#include "object_properties.h"
+#include "serveractiveobject.h"
+
+class UnitSAO: public ServerActiveObject
+{
+public:
+	UnitSAO(ServerEnvironment *env, v3f pos);
+	virtual ~UnitSAO() = default;
+
+	void setRotation(v3f rotation) { m_rotation = rotation; }
+	const v3f &getRotation() const { return m_rotation; }
+	v3f getRadRotation() { return m_rotation * core::DEGTORAD; }
+
+	// Deprecated
+	f32 getRadYawDep() const { return (m_rotation.Y + 90.) * core::DEGTORAD; }
+
+	u16 getHP() const { return m_hp; }
+	// Use a function, if isDead can be defined by other conditions
+	bool isDead() const { return m_hp == 0; }
+
+	inline bool isAttached() const
+	{ return getParent(); }
+
+	inline bool isImmortal() const
+	{ return itemgroup_get(getArmorGroups(), "immortal"); }
+
+	void setArmorGroups(const ItemGroupList &armor_groups);
+	const ItemGroupList &getArmorGroups() const;
+	void setAnimation(v2f frame_range, float frame_speed, float frame_blend, bool frame_loop);
+	void getAnimation(v2f *frame_range, float *frame_speed, float *frame_blend, bool *frame_loop);
+	void setAnimationSpeed(float frame_speed);
+	void setBonePosition(const std::string &bone, v3f position, v3f rotation);
+	void getBonePosition(const std::string &bone, v3f *position, v3f *rotation);
+	void setAttachment(int parent_id, const std::string &bone, v3f position, v3f rotation);
+	void getAttachment(int *parent_id, std::string *bone, v3f *position,
+			v3f *rotation) const;
+	void clearChildAttachments();
+	void clearParentAttachment();
+	void addAttachmentChild(int child_id);
+	void removeAttachmentChild(int child_id);
+	const std::unordered_set<int> &getAttachmentChildIds() const;
+	ServerActiveObject *getParent() const;
+	ObjectProperties* accessObjectProperties();
+	void notifyObjectPropertiesModified();
+
+	std::string generateUpdateAttachmentCommand() const;
+	std::string generateUpdateAnimationSpeedCommand() const;
+	std::string generateUpdateAnimationCommand() const;
+	std::string generateUpdateArmorGroupsCommand() const;
+	static std::string generateUpdatePositionCommand(const v3f &position, const v3f &velocity,
+			const v3f &acceleration, const v3f &rotation, bool do_interpolate,
+			bool is_movement_end, f32 update_interval);
+	std::string generateSetPropertiesCommand(const ObjectProperties &prop) const;
+	void sendPunchCommand();
+	static std::string generateUpdateBonePositionCommand(const std::string &bone,
+		const v3f &position, const v3f &rotation);
+
+protected:
+	u16 m_hp = 1;
+
+	v3f m_rotation;
+
+	bool m_properties_sent = true;
+	ObjectProperties m_prop;
+
+	ItemGroupList m_armor_groups;
+	bool m_armor_groups_sent = false;
+
+	v2f m_animation_range;
+	float m_animation_speed = 0.0f;
+	float m_animation_blend = 0.0f;
+	bool m_animation_loop = true;
+	bool m_animation_sent = false;
+	bool m_animation_speed_sent = false;
+
+	// Stores position and rotation for each bone name
+	std::unordered_map<std::string, core::vector2d<v3f>> m_bone_position;
+	bool m_bone_position_sent = false;
+
+	int m_attachment_parent_id = 0;
+	std::unordered_set<int> m_attachment_child_ids;
+	std::string m_attachment_bone = "";
+	v3f m_attachment_position;
+	v3f m_attachment_rotation;
+	bool m_attachment_sent = false;
+private:
+	void onAttach(int parent_id);
+	void onDetach(int parent_id);
+
+	std::string generatePunchCommand(u16 result_hp) const;
+};