[CSM] Add send_chat_message and run_server_chatcommand API functions (#5747)

* [CSM] Add send_chat_message and run_server_chatcommand API functions

* Add client-side chat message rate limiting

* Limit out chat queue size

* [CSM] Add minetest.clear_out_chat_queue API function and .clear_chat_queue chatcommand

* Last fixes/cleanups before merge

9 files changed, 111 insertions, 6 deletions

diff --git a/builtin/client/chatcommands.lua b/builtin/client/chatcommands.lua
index f425216f5..2b8cc4acd 100644
--- a/builtin/client/chatcommands.lua
+++ b/builtin/client/chatcommands.lua
@@ -51,3 +51,15 @@ core.register_chatcommand("disconnect", {
 		core.disconnect()
 	end,
 })
+
+core.register_chatcommand("clear_chat_queue", {
+	description = core.gettext("Clear the out chat queue"),
+	func = function(param)
+		core.clear_out_chat_queue()
+		return true, core.gettext("The out chat queue is now empty")
+	end,
+})
+
+function core.run_server_chatcommand(cmd, param)
+	core.send_chat_message("/" .. cmd .. " " .. param)
+end
diff --git a/builtin/settingtypes.txt b/builtin/settingtypes.txt
index 463ca0be9..0ec33c628 100644
--- a/builtin/settingtypes.txt
+++ b/builtin/settingtypes.txt
@@ -312,6 +312,9 @@ serverlist_url (Serverlist URL) string servers.minetest.net
 #    File in client/serverlist/ that contains your favorite servers displayed in the Multiplayer Tab.
 serverlist_file (Serverlist file) string favoriteservers.txt
 
+#    Maximum size of the out chat queue. 0 to disable queueing and -1 to make the queue size unlimited
+max_out_chat_queue_size (Maximum size of the out chat queue) int 20
+
 [*Graphics]
 
 [**In-Game]
diff --git a/doc/client_lua_api.md b/doc/client_lua_api.md
index ce0746df4..b3e494cc1 100644
--- a/doc/client_lua_api.md
+++ b/doc/client_lua_api.md
@@ -721,6 +721,12 @@ Call these functions only at load time!
 ### Player
 * `minetest.get_wielded_item()`
     * Returns the itemstack the local player is holding
+* `minetest.send_chat_message(message)`
+    * Act as if `message` was typed by the player into the terminal.
+* `minetest.run_server_chatcommand(cmd, param)`
+    * Alias for `minetest.send_chat_message("/" .. cmd .. " " .. param)`
+* `minetest.clear_out_chat_queue()`
+    * Clears the out chat queue
 * `minetest.localplayer`
     * Reference to the LocalPlayer object. See [`LocalPlayer`](#localplayer) class reference for methods.
 
@@ -836,7 +842,7 @@ Please do not try to access the reference until the camera is initialized, other
     * Returns with same syntax as above
 * `get_fov()`
     * Returns:
-    
+
 ```lua
      {
          x = number,
@@ -845,7 +851,7 @@ Please do not try to access the reference until the camera is initialized, other
          actual = number
      }
 ```
-    
+
 * `get_pos()`
     * Returns position of camera with view bobbing
 * `get_offset()`
diff --git a/minetest.conf.example b/minetest.conf.example
index e9add1597..5e1609de6 100644
--- a/minetest.conf.example
+++ b/minetest.conf.example
@@ -343,6 +343,10 @@
 #    type: string
 # serverlist_file = favoriteservers.txt
 
+#    Maximum size of the out chat queue. 0 to disable queueing and -1 to make the queue size unlimited
+#    type: int min: -1
+max_out_chat_queue_size = 20
+
 ## Graphics
 
 ### In-Game
diff --git a/src/client.cpp b/src/client.cpp
index a36f5413f..a5228132d 100644
--- a/src/client.cpp
+++ b/src/client.cpp
@@ -104,6 +104,8 @@ Client::Client(
 	m_animation_time(0),
 	m_crack_level(-1),
 	m_crack_pos(0,0,0),
+	m_last_chat_message_sent(time(NULL)),
+	m_chat_message_allowance(5.0f),
 	m_map_seed(0),
 	m_password(password),
 	m_chosen_auth_mech(AUTH_MECHANISM_NONE),
@@ -401,6 +403,14 @@ void Client::step(float dtime)
 	}
 
 	/*
+		Send pending messages on out chat queue
+	*/
+	if (!m_out_chat_queue.empty() && canSendChatMessage()) {
+		sendChatMessage(m_out_chat_queue.front());
+		m_out_chat_queue.pop();
+	}
+
+	/*
 		Handle environment
 	*/
 	// Control local player (0ms)
@@ -1158,13 +1168,50 @@ void Client::sendInventoryAction(InventoryAction *a)
 	Send(&pkt);
 }
 
+bool Client::canSendChatMessage() const
+{
+	u32 now = time(NULL);
+	float time_passed = now - m_last_chat_message_sent;
+
+	float virt_chat_message_allowance = m_chat_message_allowance + time_passed *
+			(CLIENT_CHAT_MESSAGE_LIMIT_PER_10S / 8.0f);
+
+	if (virt_chat_message_allowance < 1.0f)
+		return false;
+
+	return true;
+}
+
 void Client::sendChatMessage(const std::wstring &message)
 {
-	NetworkPacket pkt(TOSERVER_CHAT_MESSAGE, 2 + message.size() * sizeof(u16));
+	const s16 max_queue_size = g_settings->getS16("max_out_chat_queue_size");
+	if (canSendChatMessage()) {
+		u32 now = time(NULL);
+		float time_passed = now - m_last_chat_message_sent;
+		m_last_chat_message_sent = time(NULL);
 
-	pkt << message;
+		m_chat_message_allowance += time_passed * (CLIENT_CHAT_MESSAGE_LIMIT_PER_10S / 8.0f);
+		if (m_chat_message_allowance > CLIENT_CHAT_MESSAGE_LIMIT_PER_10S)
+			m_chat_message_allowance = CLIENT_CHAT_MESSAGE_LIMIT_PER_10S;
 
-	Send(&pkt);
+		m_chat_message_allowance -= 1.0f;
+
+		NetworkPacket pkt(TOSERVER_CHAT_MESSAGE, 2 + message.size() * sizeof(u16));
+
+		pkt << message;
+
+		Send(&pkt);
+	} else if (m_out_chat_queue.size() < (u16) max_queue_size || max_queue_size == -1) {
+		m_out_chat_queue.push(message);
+	} else {
+		infostream << "Could not queue chat message because maximum out chat queue size ("
+				<< max_queue_size << ") is reached." << std::endl;
+	}
+}
+
+void Client::clearOutChatQueue()
+{
+	m_out_chat_queue = std::queue<std::wstring>();
 }
 
 void Client::sendChangePassword(const std::string &oldpassword,
@@ -1924,4 +1971,3 @@ std::string Client::getModStoragePath() const
 {
 	return porting::path_user + DIR_DELIM + "client" + DIR_DELIM + "mod_storage";
 }
-
diff --git a/src/client.h b/src/client.h
index cc0d4699d..b4145c76f 100644
--- a/src/client.h
+++ b/src/client.h
@@ -38,6 +38,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "tileanimation.h"
 #include "mesh_generator_thread.h"
 
+#define CLIENT_CHAT_MESSAGE_LIMIT_PER_10S 10.0f
+
 struct MeshMakeData;
 class MapBlockMesh;
 class IWritableTextureSource;
@@ -360,6 +362,7 @@ public:
 		const StringMap &fields);
 	void sendInventoryAction(InventoryAction *a);
 	void sendChatMessage(const std::wstring &message);
+	void clearOutChatQueue();
 	void sendChangePassword(const std::string &oldpassword,
 		const std::string &newpassword);
 	void sendDamage(u8 damage);
@@ -565,6 +568,8 @@ private:
 	inline std::string getPlayerName()
 	{ return m_env.getLocalPlayer()->getName(); }
 
+	bool canSendChatMessage() const;
+
 	float m_packetcounter_timer;
 	float m_connection_reinit_timer;
 	float m_avg_rtt_timer;
@@ -612,6 +617,9 @@ private:
 	//s32 m_daynight_i;
 	//u32 m_daynight_ratio;
 	std::queue<std::wstring> m_chat_queue;
+	std::queue<std::wstring> m_out_chat_queue;
+	u32 m_last_chat_message_sent;
+	float m_chat_message_allowance;
 
 	// The authentication methods we can use to enter sudo mode (=change password)
 	u32 m_sudo_auth_methods;
diff --git a/src/defaultsettings.cpp b/src/defaultsettings.cpp
index c583220bd..0a44069fd 100644
--- a/src/defaultsettings.cpp
+++ b/src/defaultsettings.cpp
@@ -57,6 +57,7 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("curl_verify_cert", "true");
 	settings->setDefault("enable_remote_media_server", "true");
 	settings->setDefault("enable_client_modding", "false");
+	settings->setDefault("max_out_chat_queue_size", "20");
 
 	// Keymap
 	settings->setDefault("remote_port", "30000");
diff --git a/src/script/lua_api/l_client.cpp b/src/script/lua_api/l_client.cpp
index 09b832ccf..0b7450af2 100644
--- a/src/script/lua_api/l_client.cpp
+++ b/src/script/lua_api/l_client.cpp
@@ -85,6 +85,23 @@ int ModApiClient::l_display_chat_message(lua_State *L)
 	return 1;
 }
 
+// send_chat_message(message)
+int ModApiClient::l_send_chat_message(lua_State *L)
+{
+	if (!lua_isstring(L,1))
+		return 0;
+	std::string message = luaL_checkstring(L, 1);
+	getClient(L)->sendChatMessage(utf8_to_wide(message));
+	return 0;
+}
+
+// clear_out_chat_queue()
+int ModApiClient::l_clear_out_chat_queue(lua_State *L)
+{
+	getClient(L)->clearOutChatQueue();
+	return 0;
+}
+
 // get_player_names()
 int ModApiClient::l_get_player_names(lua_State *L)
 {
@@ -317,6 +334,8 @@ void ModApiClient::Initialize(lua_State *L, int top)
 	API_FCT(get_current_modname);
 	API_FCT(print);
 	API_FCT(display_chat_message);
+	API_FCT(send_chat_message);
+	API_FCT(clear_out_chat_queue);
 	API_FCT(get_player_names);
 	API_FCT(set_last_run_mod);
 	API_FCT(get_last_run_mod);
diff --git a/src/script/lua_api/l_client.h b/src/script/lua_api/l_client.h
index 09b74addd..fe5780fb1 100644
--- a/src/script/lua_api/l_client.h
+++ b/src/script/lua_api/l_client.h
@@ -37,6 +37,12 @@ private:
 	// display_chat_message(message)
 	static int l_display_chat_message(lua_State *L);
 
+	// send_chat_message(message)
+	static int l_send_chat_message(lua_State *L);
+
+	// clear_out_chat_queue()
+	static int l_clear_out_chat_queue(lua_State *L);
+
 	// get_player_names()
 	static int l_get_player_names(lua_State *L);