Allow damage for attached objects, add attach/detach callbacks (#6786)

* Allow right-clicking on attached LuaEntities

9 files changed, 133 insertions, 75 deletions

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 5442612af..dae3452a1 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -4868,6 +4868,13 @@ Registered entities
         * Called when the object dies.
         * `killer`: an `ObjectRef` (can be `nil`)
     * `on_rightclick(self, clicker)`
+    * `on_attach_child(self, child)`
+        * `child`: an `ObjectRef` (can be `nil`) of the child that attaches
+    * `on_detach_child(self, child)`
+        * `child`: an `ObjectRef` (can be `nil`) of the child that detaches
+    * `on_detach(self, parent)`
+        * `parent`: an `ObjectRef` (can be `nil`) from where it got detached
+        * This happens before the parent object is removed from the world
     * `get_staticdata(self)`
         * Should return a string that will be passed to `on_activate` when
           the object is instantiated the next time.
diff --git a/src/content_cao.cpp b/src/content_cao.cpp
index 4dde1b098..9344b3370 100644
--- a/src/content_cao.cpp
+++ b/src/content_cao.cpp
@@ -343,7 +343,7 @@ GenericCAO::~GenericCAO()
 bool GenericCAO::getSelectionBox(aabb3f *toset) const
 {
 	if (!m_prop.is_visible || !m_is_visible || m_is_local_player
-			|| !m_prop.pointable || getParent() != NULL) {
+			|| !m_prop.pointable) {
 		return false;
 	}
 	*toset = m_selection_box;
@@ -430,6 +430,7 @@ void GenericCAO::removeFromScene(bool permanent)
 				m_env->attachement_parent_ids[ci] = 0;
 			}
 		}
+		m_children.clear();
 
 		m_env->attachement_parent_ids[getId()] = 0;
 
@@ -1409,17 +1410,18 @@ void GenericCAO::processMessage(const std::string &data)
 
 		updateBonePosition();
 	} else if (cmd == GENERIC_CMD_ATTACH_TO) {
-		u16 parentID = readS16(is);
-		u16 oldparent = m_env->attachement_parent_ids[getId()];
-		if (oldparent) {
-			m_children.erase(std::remove(m_children.begin(), m_children.end(),
-				getId()), m_children.end());
-		}
-		m_env->attachement_parent_ids[getId()] = parentID;
-		GenericCAO *parentobj = m_env->getGenericCAO(parentID);
+		u16 parent_id = readS16(is);
+		u16 &old_parent_id = m_env->attachement_parent_ids[getId()];
+		if (parent_id != old_parent_id) {
+			if (GenericCAO *old_parent = m_env->getGenericCAO(old_parent_id)) {
+				old_parent->m_children.erase(std::remove(
+					m_children.begin(), m_children.end(),
+					getId()), m_children.end());
+			}
+			if (GenericCAO *new_parent = m_env->getGenericCAO(parent_id))
+				new_parent->m_children.push_back(getId());
 
-		if (parentobj) {
-			parentobj->m_children.push_back(getId());
+			old_parent_id = parent_id;
 		}
 
 		m_attachment_bone = deSerializeString(is);
diff --git a/src/content_sao.cpp b/src/content_sao.cpp
index c554b775d..1c049c727 100644
--- a/src/content_sao.cpp
+++ b/src/content_sao.cpp
@@ -187,11 +187,17 @@ void UnitSAO::setAttachment(int parent_id, const std::string &bone, v3f position
 	// 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,
@@ -203,6 +209,30 @@ void UnitSAO::getAttachment(int *parent_id, std::string *bone, v3f *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);
@@ -218,6 +248,38 @@ const std::unordered_set<int> &UnitSAO::getAttachmentChildIds()
 	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;
@@ -548,10 +610,6 @@ int LuaEntitySAO::punch(v3f dir,
 		return 0;
 	}
 
-	// It's best that attachments cannot be punched
-	if (isAttached())
-		return 0;
-
 	ItemStack *punchitem = NULL;
 	ItemStack punchitem_static;
 	if (puncher) {
@@ -588,8 +646,10 @@ int LuaEntitySAO::punch(v3f dir,
 		}
 	}
 
-	if (getHP() == 0) {
+	if (getHP() == 0 && !isGone()) {
 		m_pending_removal = true;
+		clearParentAttachment();
+		clearChildAttachments();
 		m_env->getScriptIface()->luaentity_on_death(m_id, puncher);
 	}
 
@@ -600,9 +660,7 @@ void LuaEntitySAO::rightClick(ServerActiveObject *clicker)
 {
 	if (!m_registered)
 		return;
-	// It's best that attachments cannot be clicked
-	if (isAttached())
-		return;
+
 	m_env->getScriptIface()->luaentity_Rightclick(m_id, clicker);
 }
 
@@ -1187,10 +1245,6 @@ int PlayerSAO::punch(v3f dir,
 	ServerActiveObject *puncher,
 	float time_from_last_punch)
 {
-	// It's best that attachments cannot be punched
-	if (isAttached())
-		return 0;
-
 	if (!toolcap)
 		return 0;
 
diff --git a/src/content_sao.h b/src/content_sao.h
index 59e3b3d4b..486e2d252 100644
--- a/src/content_sao.h
+++ b/src/content_sao.h
@@ -52,6 +52,8 @@ public:
 	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);
+	void clearChildAttachments();
+	void clearParentAttachment();
 	void addAttachmentChild(int child_id);
 	void removeAttachmentChild(int child_id);
 	const std::unordered_set<int> &getAttachmentChildIds();
@@ -72,7 +74,7 @@ protected:
 	float m_animation_blend = 0.0f;
 	bool m_animation_loop = true;
 	bool m_animation_sent = false;
-        bool m_animation_speed_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;
@@ -84,6 +86,9 @@ protected:
 	v3f m_attachment_position;
 	v3f m_attachment_rotation;
 	bool m_attachment_sent = false;
+private:
+	void onAttach(int parent_id);
+	void onDetach(int parent_id);
 };
 
 /*
diff --git a/src/script/cpp_api/s_entity.cpp b/src/script/cpp_api/s_entity.cpp
index df4b77936..88dbcc620 100644
--- a/src/script/cpp_api/s_entity.cpp
+++ b/src/script/cpp_api/s_entity.cpp
@@ -262,7 +262,9 @@ bool ScriptApiEntity::luaentity_Punch(u16 id,
 	return retval;
 }
 
-bool ScriptApiEntity::luaentity_on_death(u16 id, ServerActiveObject *killer)
+// Calls entity[field](ObjectRef self, ObjectRef sao)
+bool ScriptApiEntity::luaentity_run_simple_callback(u16 id,
+	ServerActiveObject *sao, const char *field)
 {
 	SCRIPTAPI_PRECHECKHEADER
 
@@ -273,14 +275,14 @@ bool ScriptApiEntity::luaentity_on_death(u16 id, ServerActiveObject *killer)
 	int object = lua_gettop(L);
 	// State: object is at top of stack
 	// Get function
-	lua_getfield(L, -1, "on_death");
+	lua_getfield(L, -1, field);
 	if (lua_isnil(L, -1)) {
-		lua_pop(L, 2); // Pop on_death and entity
+		lua_pop(L, 2); // Pop callback field and entity
 		return false;
 	}
 	luaL_checktype(L, -1, LUA_TFUNCTION);
 	lua_pushvalue(L, object);  // self
-	objectrefGetOrCreate(L, killer);  // killer reference
+	objectrefGetOrCreate(L, sao);  // killer reference
 
 	setOriginFromTable(object);
 	PCALL_RES(lua_pcall(L, 2, 1, error_handler));
@@ -290,33 +292,28 @@ bool ScriptApiEntity::luaentity_on_death(u16 id, ServerActiveObject *killer)
 	return retval;
 }
 
-// Calls entity:on_rightclick(ObjectRef clicker)
-void ScriptApiEntity::luaentity_Rightclick(u16 id,
-		ServerActiveObject *clicker)
+bool ScriptApiEntity::luaentity_on_death(u16 id, ServerActiveObject *killer)
 {
-	SCRIPTAPI_PRECHECKHEADER
-
-	//infostream<<"scriptapi_luaentity_step: id="<<id<<std::endl;
-
-	int error_handler = PUSH_ERROR_HANDLER(L);
+	return luaentity_run_simple_callback(id, killer, "on_death");
+}
 
-	// Get core.luaentities[id]
-	luaentity_get(L, id);
-	int object = lua_gettop(L);
-	// State: object is at top of stack
-	// Get function
-	lua_getfield(L, -1, "on_rightclick");
-	if (lua_isnil(L, -1)) {
-		lua_pop(L, 2); // Pop on_rightclick and entity
-		return;
-	}
-	luaL_checktype(L, -1, LUA_TFUNCTION);
-	lua_pushvalue(L, object); // self
-	objectrefGetOrCreate(L, clicker); // Clicker reference
+// Calls entity:on_rightclick(ObjectRef clicker)
+void ScriptApiEntity::luaentity_Rightclick(u16 id, ServerActiveObject *clicker)
+{
+	luaentity_run_simple_callback(id, clicker, "on_rightclick");
+}
 
-	setOriginFromTable(object);
-	PCALL_RES(lua_pcall(L, 2, 0, error_handler));
+void ScriptApiEntity::luaentity_on_attach_child(u16 id, ServerActiveObject *child)
+{
+	luaentity_run_simple_callback(id, child, "on_attach_child");
+}
 
-	lua_pop(L, 2); // Pop object and error handler
+void ScriptApiEntity::luaentity_on_detach_child(u16 id, ServerActiveObject *child)
+{
+	luaentity_run_simple_callback(id, child, "on_detach_child");
 }
 
+void ScriptApiEntity::luaentity_on_detach(u16 id, ServerActiveObject *parent)
+{
+	luaentity_run_simple_callback(id, parent, "on_detach");
+}
diff --git a/src/script/cpp_api/s_entity.h b/src/script/cpp_api/s_entity.h
index 173e24c30..966c2745e 100644
--- a/src/script/cpp_api/s_entity.h
+++ b/src/script/cpp_api/s_entity.h
@@ -41,6 +41,11 @@ public:
 			ServerActiveObject *puncher, float time_from_last_punch,
 			const ToolCapabilities *toolcap, v3f dir, s16 damage);
 	bool luaentity_on_death(u16 id, ServerActiveObject *killer);
-	void luaentity_Rightclick(u16 id,
-			ServerActiveObject *clicker);
+	void luaentity_Rightclick(u16 id, ServerActiveObject *clicker);
+	void luaentity_on_attach_child(u16 id, ServerActiveObject *child);
+	void luaentity_on_detach_child(u16 id, ServerActiveObject *child);
+	void luaentity_on_detach(u16 id, ServerActiveObject *parent);
+private:
+	bool luaentity_run_simple_callback(u16 id, ServerActiveObject *sao,
+		const char *field);
 };
diff --git a/src/script/lua_api/l_object.cpp b/src/script/lua_api/l_object.cpp
index 0bef23541..b3c3a55bf 100644
--- a/src/script/lua_api/l_object.cpp
+++ b/src/script/lua_api/l_object.cpp
@@ -103,12 +103,8 @@ int ObjectRef::l_remove(lua_State *L)
 	if (co->getType() == ACTIVEOBJECT_TYPE_PLAYER)
 		return 0;
 
-	const std::unordered_set<int> &child_ids = co->getAttachmentChildIds();
-	for (int child_id : child_ids) {
-		// Child can be NULL if it was deleted earlier
-		if (ServerActiveObject *child = env->getActiveObject(child_id))
-			child->setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0));
-	}
+	co->clearChildAttachments();
+	co->clearParentAttachment();
 
 	verbosestream << "ObjectRef::l_remove(): id=" << co->getId() << std::endl;
 	co->m_pending_removal = true;
@@ -721,21 +717,7 @@ int ObjectRef::l_set_detach(lua_State *L)
 	if (co == NULL)
 		return 0;
 
-	int parent_id = 0;
-	std::string bone;
-	v3f position;
-	v3f rotation;
-	co->getAttachment(&parent_id, &bone, &position, &rotation);
-	ServerActiveObject *parent = NULL;
-	if (parent_id) {
-		parent = env->getActiveObject(parent_id);
-		co->setAttachment(0, "", position, rotation);
-	} else {
-		co->setAttachment(0, "", v3f(0, 0, 0), v3f(0, 0, 0));
-	}
-	// Do it
-	if (parent != NULL)
-		parent->removeAttachmentChild(co->getId());
+	co->clearParentAttachment();
 	return 0;
 }
 
diff --git a/src/server.cpp b/src/server.cpp
index dad8f1712..9d4c13325 100644
--- a/src/server.cpp
+++ b/src/server.cpp
@@ -2504,6 +2504,7 @@ void Server::DiePlayer(session_t peer_id, const PlayerHPChangeReason &reason)
 			<< " dies" << std::endl;
 
 	playersao->setHP(0, reason);
+	playersao->clearParentAttachment();
 
 	// Trigger scripted stuff
 	m_script->on_dieplayer(playersao, reason);
diff --git a/src/serverobject.h b/src/serverobject.h
index 77b701464..ba205f6a5 100644
--- a/src/serverobject.h
+++ b/src/serverobject.h
@@ -165,6 +165,8 @@ public:
 	{}
 	virtual void getAttachment(int *parent_id, std::string *bone, v3f *position, v3f *rotation)
 	{}
+	virtual void clearChildAttachments() {}
+	virtual void clearParentAttachment() {}
 	virtual void addAttachmentChild(int child_id)
 	{}
 	virtual void removeAttachmentChild(int child_id)
@@ -250,6 +252,9 @@ public:
 	std::queue<ActiveObjectMessage> m_messages_out;
 
 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,