Add server side ncurses terminal

This adds a chat console the server owner can use for administration
or to talk with players.
It runs in its own thread, which makes the user interface immune to
the server's lag, behaving just like a client, except timeout.
As it uses the same console code as the f10 console, things like nick
completion or a scroll buffer basically come for free.
The terminal itself is written in a general way so that adding a
client version later on is just about implementing an interface.

Fatal errors are printed after the console exists and the ncurses
terminal buffer gets cleaned up with endwin(), so that the error still
remains visible.

The server owner can chose their username their entered text will
have in chat and where players can send PMs to.
Once the username is secured with a password to prevent anybody to
take over the server, the owner can execute admin tasks over the
console.

This change includes a contribution by @kahrl who has improved ncurses
library detection.

src/server.cpp

@@ -148,7 +148,8 @@ Server::Server(
 		const std::string &path_world,
 		const SubgameSpec &gamespec,
 		bool simple_singleplayer_mode,
-		bool ipv6
+		bool ipv6,
+		ChatInterface *iface
 	):
 	m_path_world(path_world),
 	m_gamespec(gamespec),
@@ -175,6 +176,7 @@ Server::Server(
 	m_clients(&m_con),
 	m_shutdown_requested(false),
 	m_shutdown_ask_reconnect(false),
+	m_admin_chat(iface),
 	m_ignore_map_edit_events(false),
 	m_ignore_map_edit_events_peer_id(0),
 	m_next_sound_id(0)
@@ -575,6 +577,36 @@ void Server::AsyncRunStep(bool initial_step)
 			U32_MAX);
 	}
 
+	/*
+		Listen to the admin chat, if available
+	*/
+	if (m_admin_chat) {
+		if (!m_admin_chat->command_queue.empty()) {
+			MutexAutoLock lock(m_env_mutex);
+			while (!m_admin_chat->command_queue.empty()) {
+				ChatEvent *evt = m_admin_chat->command_queue.pop_frontNoEx();
+				if (evt->type == CET_NICK_ADD) {
+					// The terminal informed us of its nick choice
+					m_admin_nick = ((ChatEventNick *)evt)->nick;
+					if (!m_script->getAuth(m_admin_nick, NULL, NULL)) {
+						errorstream << "You haven't set up an account." << std::endl
+							<< "Please log in using the client as '"
+							<< m_admin_nick << "' with a secure password." << std::endl
+							<< "Until then, you can't execute admin tasks via the console," << std::endl
+							<< "and everybody can claim the user account instead of you," << std::endl
+							<< "giving them full control over this server." << std::endl;
+					}
+				} else {
+					assert(evt->type == CET_CHAT);
+					handleAdminChat((ChatEventChat *)evt);
+				}
+				delete evt;
+			}
+		}
+		m_admin_chat->outgoing_queue.push_back(
+			new ChatEventTimeInfo(m_env->getGameTime(), m_env->getTimeOfDay()));
+	}
+
 	/*
 		Do background stuff
 	*/
@@ -1100,16 +1132,19 @@ PlayerSAO* Server::StageTwoClientInit(u16 peer_id)
 
 		// Send information about joining in chat
 		{
-			std::wstring name = L"unknown";
+			std::string name = "unknown";
 			Player *player = m_env->getPlayer(peer_id);
 			if(player != NULL)
-				name = narrow_to_wide(player->getName());
+				name = player->getName();
 
 			std::wstring message;
 			message += L"*** ";
-			message += name;
+			message += narrow_to_wide(name);
 			message += L" joined the game.";
 			SendChatMessage(PEER_ID_INEXISTENT,message);
+			if (m_admin_chat)
+				m_admin_chat->outgoing_queue.push_back(
+					new ChatEventNick(CET_NICK_ADD, name));
 		}
 	}
 	Address addr = getPeerAddress(player->peer_id);
@@ -1432,6 +1467,16 @@ void Server::handlePeerChanges()
 	}
 }
 
+void Server::printToConsoleOnly(const std::string &text)
+{
+	if (m_admin_chat) {
+		m_admin_chat->outgoing_queue.push_back(
+			new ChatEventChat("", utf8_to_wide(text)));
+	} else {
+		std::cout << text;
+	}
+}
+
 void Server::Send(NetworkPacket* pkt)
 {
 	m_clients.send(pkt->getPeerId(),
@@ -2665,9 +2710,13 @@ void Server::DeleteClient(u16 peer_id, ClientDeletionReason reason)
 					os << player->getName() << " ";
 				}
 
-				actionstream << player->getName() << " "
+				std::string name = player->getName();
+				actionstream << name << " "
 						<< (reason == CDR_TIMEOUT ? "times out." : "leaves game.")
 						<< " List of players: " << os.str() << std::endl;
+				if (m_admin_chat)
+					m_admin_chat->outgoing_queue.push_back(
+						new ChatEventNick(CET_NICK_REMOVE, name));
 			}
 		}
 		{
@@ -2700,6 +2749,77 @@ void Server::UpdateCrafting(Player* player)
 	plist->changeItem(0, preview);
 }
 
+std::wstring Server::handleChat(const std::string &name, const std::wstring &wname,
+	const std::wstring &wmessage, u16 peer_id_to_avoid_sending)
+{
+	// If something goes wrong, this player is to blame
+	RollbackScopeActor rollback_scope(m_rollback,
+		std::string("player:") + name);
+
+	// Line to send
+	std::wstring line;
+	// Whether to send line to the player that sent the message, or to all players
+	bool broadcast_line = true;
+
+	// Run script hook
+	bool ate = m_script->on_chat_message(name,
+		wide_to_utf8(wmessage));
+	// If script ate the message, don't proceed
+	if (ate)
+		return L"";
+
+	// Commands are implemented in Lua, so only catch invalid
+	// commands that were not "eaten" and send an error back
+	if (wmessage[0] == L'/') {
+		std::wstring wcmd = wmessage.substr(1);
+		broadcast_line = false;
+		if (wcmd.length() == 0)
+			line += L"-!- Empty command";
+		else
+			line += L"-!- Invalid command: " + str_split(wcmd, L' ')[0];
+	} else {
+		line += L"<";
+		line += wname;
+		line += L"> ";
+		line += wmessage;
+	}
+
+	/*
+		Tell calling method to send the message to sender
+	*/
+	if (!broadcast_line) {
+		return line;
+	} else {
+		/*
+			Send the message to others
+		*/
+		actionstream << "CHAT: " << wide_to_narrow(line) << std::endl;
+
+		std::vector<u16> clients = m_clients.getClientIDs();
+
+		for (u16 i = 0; i < clients.size(); i++) {
+			u16 cid = clients[i];
+			if (cid != peer_id_to_avoid_sending)
+				SendChatMessage(cid, line);
+		}
+	}
+	return L"";
+}
+
+void Server::handleAdminChat(const ChatEventChat *evt)
+{
+	std::string name = evt->nick;
+	std::wstring wname = utf8_to_wide(name);
+	std::wstring wmessage = evt->evt_msg;
+
+	std::wstring answer = handleChat(name, wname, wmessage);
+
+	// If asked to send answer to sender
+	if (!answer.empty()) {
+		m_admin_chat->outgoing_queue.push_back(new ChatEventChat("", answer));
+	}
+}
+
 RemoteClient* Server::getClient(u16 peer_id, ClientState state_min)
 {
 	RemoteClient *client = getClientNoEx(peer_id,state_min);
@@ -2831,9 +2951,14 @@ void Server::notifyPlayer(const char *name, const std::wstring &msg)
 	if (!m_env)
 		return;
 
+	if (m_admin_nick == name && !m_admin_nick.empty()) {
+		m_admin_chat->outgoing_queue.push_back(new ChatEventChat("", msg));
+	}
+
 	Player *player = m_env->getPlayer(name);
-	if (!player)
+	if (!player) {
 		return;
+	}
 
 	if (player->peer_id == PEER_ID_INEXISTENT)
 		return;