add: New map voting mode "Notriples" - next map can't be selected if played twice in a row

code/controllers/subsystem/non-firing/mapping.dm

@@ -41,6 +41,8 @@ SUBSYSTEM_DEF(mapping)
 	var/list/critical_planes
 	/// The largest plane offset we've generated so far
 	var/max_plane_offset = 0
+	/// Maps played in previous rounds, stores typepaths
+	var/list/previous_maps
 
 
 // This has to be here because world/New() uses [station_name()], which looks this datum up
@@ -57,17 +59,51 @@ SUBSYSTEM_DEF(mapping)
 		catch
 			map_datum = fallback_map // Assume delta if non-existent
 		fdel("data/next_map.txt") // Remove to avoid the same map existing forever
+
 		return
+
 	map_datum = fallback_map // Assume delta if non-existent
 
 /datum/controller/subsystem/mapping/Shutdown()
 	if(next_map) // Save map for next round
 		var/F = file("data/next_map.txt")
 		F << next_map.type
 
+
+/datum/controller/subsystem/mapping/proc/convert_map_datums()
+	var/list/map_subtypes = subtypesof(/datum/map)
+	var/list/result = list()
+	for(var/datum/map/subtype as anything in map_subtypes)
+		result[initial(subtype.name)] = subtype
+
+	return result
+
+/datum/controller/subsystem/mapping/proc/find_last_played_maps()
+	if(CONFIG_GET(flag/sql_enabled))
+		var/datum/db_query/query = \
+		SSdbcore.NewQuery("SELECT id, map_name \
+		FROM [format_table_name("round")] \
+		WHERE server_port=[world.port] \
+		AND end_state IS NOT NULL \
+		ORDER BY id DESC LIMIT 1") //Generally gets the last played map, but can be configured to get any count.
+
+		if(!query.warn_execute())
+			qdel(query)
+			return
+
+		var/list/map_names = convert_map_datums()
+		var/list/maps = list()
+		//Query row structure: id, map_name
+		for(var/map in query.rows)
+			var/map_path = map_names[map[2]]
+			if(map_path)
+				maps += map_path
+
+		previous_maps = maps
+
 /datum/controller/subsystem/mapping/Initialize()
 	setupPlanes()
-
+	find_last_played_maps()
 	var/datum/lavaland_theme/lavaland_theme_type = pick(subtypesof(/datum/lavaland_theme))
 	ASSERT(lavaland_theme_type)
 	lavaland_theme = new lavaland_theme_type

code/modules/vote/vote_presets.dm

@@ -31,6 +31,12 @@
 	if(CONFIG_GET(string/map_vote_mode) == "nodoubles")
 		map_pool -= SSmapping.map_datum.type
 
+	if(CONFIG_GET(string/map_vote_mode) == "notriples")
+		if(SSmapping.previous_maps && length(SSmapping.previous_maps))
+			var/current_map = SSmapping.map_datum.type
+			if(current_map == SSmapping.previous_maps[1])
+				map_pool -= current_map
+
 	for(var/datum/map/possible_map as anything in map_pool)
 		if(initial(possible_map.admin_only))
 			continue

config/example/config.txt

@@ -663,6 +663,7 @@ MAP_ROTATE none
 ## Server map voting mode:
 ## all - all maps can be selected
 ## nodoubles - current map can't be selected as next
+## notriples - current map can't be selected as next if played twice in a row
 MAP_VOTE_MODE all
 
 ## Default server map