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.

1 files changed, 83 insertions, 14 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 48b1af603..5046181b5 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -45,10 +45,15 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "httpfetch.h"
 #include "guiEngine.h"
 #include "map.h"
+#include "player.h"
 #include "mapsector.h"
 #include "fontengine.h"
 #include "gameparams.h"
 #include "database.h"
+#include "config.h"
+#if USE_CURSES
+	#include "terminal_chat_console.h"
+#endif
 #ifndef SERVER
 #include "client/clientlauncher.h"
 #endif
@@ -277,6 +282,8 @@ static void set_allowed_options(OptionList *allowed_options)
 			_("Set gameid (\"--gameid list\" prints available ones)"))));
 	allowed_options->insert(std::make_pair("migrate", ValueSpec(VALUETYPE_STRING,
 			_("Migrate from current map backend to another (Only works when using minetestserver or with --server)"))));
+	allowed_options->insert(std::make_pair("terminal", ValueSpec(VALUETYPE_FLAG,
+			_("Feature an interactive terminal (Only works when using minetestserver or with --server)"))));
 #ifndef SERVER
 	allowed_options->insert(std::make_pair("videomodes", ValueSpec(VALUETYPE_FLAG,
 			_("Show available video modes"))));
@@ -816,21 +823,83 @@ static bool run_dedicated_server(const GameParams &game_params, const Settings &
 	if (cmd_args.exists("migrate"))
 		return migrate_database(game_params, cmd_args);
 
-	try {
-		// Create server
-		Server server(game_params.world_path, game_params.game_spec, false,
-			bind_addr.isIPv6());
-		server.start(bind_addr);
-
-		// Run server
+	if (cmd_args.exists("terminal")) {
+#if USE_CURSES
+		bool name_ok = true;
+		std::string admin_nick = g_settings->get("name");
+
+		name_ok = name_ok && !admin_nick.empty();
+		name_ok = name_ok && string_allowed(admin_nick, PLAYERNAME_ALLOWED_CHARS);
+
+		if (!name_ok) {
+			if (admin_nick.empty()) {
+				errorstream << "No name given for admin. "
+					<< "Please check your minetest.conf that it "
+					<< "contains a 'name = ' to your main admin account."
+					<< std::endl;
+			} else {
+				errorstream << "Name for admin '"
+					<< admin_nick << "' is not valid. "
+					<< "Please check that it only contains allowed characters. "
+					<< "Valid characters are: " << PLAYERNAME_ALLOWED_CHARS_USER_EXPL
+					<< std::endl;
+			}
+			return false;
+		}
+		ChatInterface iface;
 		bool &kill = *porting::signal_handler_killstatus();
-		dedicated_server_loop(server, kill);
-	} catch (const ModError &e) {
-		errorstream << "ModError: " << e.what() << std::endl;
-		return false;
-	} catch (const ServerError &e) {
-		errorstream << "ServerError: " << e.what() << std::endl;
-		return false;
+
+		try {
+			// Create server
+			Server server(game_params.world_path,
+				game_params.game_spec, false, bind_addr.isIPv6(), &iface);
+
+			g_term_console.setup(&iface, &kill, admin_nick);
+
+			g_term_console.start();
+
+			server.start(bind_addr);
+			// Run server
+			dedicated_server_loop(server, kill);
+		} catch (const ModError &e) {
+			g_term_console.stopAndWaitforThread();
+			errorstream << "ModError: " << e.what() << std::endl;
+			return false;
+		} catch (const ServerError &e) {
+			g_term_console.stopAndWaitforThread();
+			errorstream << "ServerError: " << e.what() << std::endl;
+			return false;
+		}
+
+		// Tell the console to stop, and wait for it to finish,
+		// only then leave context and free iface
+		g_term_console.stop();
+		g_term_console.wait();
+
+		g_term_console.clearKillStatus();
+	} else {
+#else
+		errorstream << "Cmd arg --terminal passed, but "
+			<< "compiled without ncurses. Ignoring." << std::endl;
+	} {
+#endif
+		try {
+			// Create server
+			Server server(game_params.world_path, game_params.game_spec, false,
+				bind_addr.isIPv6());
+			server.start(bind_addr);
+
+			// Run server
+			bool &kill = *porting::signal_handler_killstatus();
+			dedicated_server_loop(server, kill);
+
+		} catch (const ModError &e) {
+			errorstream << "ModError: " << e.what() << std::endl;
+			return false;
+		} catch (const ServerError &e) {
+			errorstream << "ServerError: " << e.what() << std::endl;
+			return false;
+		}
 	}
 
 	return true;