Multiz and isolated ruins support. (#47336)

Two new always_load_with options for ruins.
Use PLACE_ISOLATED to load the secondary ruin part in separate z level.
Use PLACE_BELOW to load it on the z level below.

code/modules/mapping/ruins.dm

@@ -1,10 +1,12 @@
-/datum/map_template/ruin/proc/try_to_place(z,allowed_areas)
-	var/sanity = PLACEMENT_TRIES
+/datum/map_template/ruin/proc/try_to_place(z,allowed_areas,turf/forced_turf)
+	var/sanity = forced_turf ? 1 : PLACEMENT_TRIES
+	if(SSmapping.level_trait(z,ZTRAIT_ISOLATED_RUINS))
+		return place_on_isolated_level(z)
 	while(sanity > 0)
 		sanity--
 		var/width_border = TRANSITIONEDGE + SPACERUIN_MAP_EDGE_PAD + round(width / 2)
 		var/height_border = TRANSITIONEDGE + SPACERUIN_MAP_EDGE_PAD + round(height / 2)
-		var/turf/central_turf = locate(rand(width_border, world.maxx - width_border), rand(height_border, world.maxy - height_border), z)
+		var/turf/central_turf = forced_turf ? forced_turf : locate(rand(width_border, world.maxx - width_border), rand(height_border, world.maxy - height_border), z)
 		var/valid = TRUE
 
 		for(var/turf/check in get_affected_turfs(central_turf,1))
@@ -34,8 +36,20 @@
 			T.flags_1 |= NO_RUINS_1
 
 		new /obj/effect/landmark/ruin(central_turf, src)
-		return TRUE
-	return FALSE
+		return central_turf
+
+/datum/map_template/ruin/proc/place_on_isolated_level(z)
+	var/datum/turf_reservation/reservation = SSmapping.RequestBlockReservation(width, height, z) //Make the new level creation work with different traits.
+	if(!reservation)
+		return
+	var/turf/placement = locate(reservation.bottom_left_coords[1],reservation.bottom_left_coords[2],reservation.bottom_left_coords[3])
+	load(placement)
+	loaded++
+	for(var/turf/T in get_affected_turfs(placement))
+		T.flags_1 |= NO_RUINS_1
+	var/turf/center = locate(placement.x + round(width/2),placement.y + round(height/2),placement.z)
+	new /obj/effect/landmark/ruin(center, src)
+	return center
 
 
 /proc/seedRuins(list/z_levels = null, budget = 0, whitelist = /area/space, list/potentialRuins)
@@ -51,9 +65,8 @@
 
 	var/list/ruins = potentialRuins.Copy()
 
-	var/list/forced_ruins = list()		//These go first on the z level associated (same random one by default)
+	var/list/forced_ruins = list()		//These go first on the z level associated (same random one by default) or if the assoc value is a turf to the specified turf.
 	var/list/ruins_availible = list()	//we can try these in the current pass
-	var/forced_z	//If set we won't pick z level and use this one instead.
 
 	//Set up the starting ruin list
 	for(var/key in ruins)
@@ -65,31 +78,51 @@
 		if(R.unpickable)
 			continue
 		ruins_availible[R] = R.placement_weight
-
 	while(budget > 0 && (ruins_availible.len || forced_ruins.len))
 		var/datum/map_template/ruin/current_pick
 		var/forced = FALSE
+		var/forced_z	//If set we won't pick z level and use this one instead.
+		var/forced_turf //If set we place the ruin centered on the given turf
 		if(forced_ruins.len) //We have something we need to load right now, so just pick it
 			for(var/ruin in forced_ruins)
 				current_pick = ruin
-				if(forced_ruins[ruin] > 0) //Load into designated z
+				if(isturf(forced_ruins[ruin]))
+					var/turf/T = forced_ruins[ruin]
+					forced_z = T.z //In case of chained ruins
+					forced_turf = T
+				else if(forced_ruins[ruin] > 0) //Load into designated z
 					forced_z = forced_ruins[ruin]
 				forced = TRUE
 				break
 		else //Otherwise just pick random one
 			current_pick = pickweight(ruins_availible)
-
-		var/placement_tries = PLACEMENT_TRIES
+		
+		var/placement_tries = forced_turf ? 1 : PLACEMENT_TRIES //Only try once if we target specific turf
 		var/failed_to_place = TRUE
-		var/z_placed = 0
-		while(placement_tries > 0)
-			placement_tries--
-			z_placed = pick(z_levels)
-			if(!current_pick.try_to_place(forced_z ? forced_z : z_placed,whitelist))
-				continue
-			else
-				failed_to_place = FALSE
-				break
+		var/target_z = 0
+		var/turf/placed_turf //Where the ruin ended up if we succeeded
+		outer:
+			while(placement_tries > 0)
+				placement_tries--
+				target_z = pick(z_levels)
+				if(forced_z)
+					target_z = forced_z
+				if(current_pick.always_spawn_with) //If the ruin has part below, make sure that z exists.
+					for(var/v in current_pick.always_spawn_with)
+						if(current_pick.always_spawn_with[v] == PLACE_BELOW)
+							var/turf/T = locate(1,1,target_z)
+							if(!SSmapping.get_turf_below(T))
+								if(forced_z)
+									continue outer
+								else
+									break outer
+
+				placed_turf = current_pick.try_to_place(target_z,whitelist,forced_turf)
+				if(!placed_turf)
+					continue
+				else
+					failed_to_place = FALSE
+					break
 
 		//That's done remove from priority even if it failed
 		if(forced)
@@ -120,18 +153,21 @@
 						if(istype(linked,v))
 							switch(current_pick.always_spawn_with[v])
 								if(PLACE_SAME_Z)
-									forced_ruins[linked] = forced_z ? forced_z : z_placed //I guess you might want a chain somehow
+									forced_ruins[linked] = target_z //I guess you might want a chain somehow
 								if(PLACE_LAVA_RUIN)
 									forced_ruins[linked] = pick(SSmapping.levels_by_trait(ZTRAIT_LAVA_RUINS))
 								if(PLACE_SPACE_RUIN)
 									forced_ruins[linked] = pick(SSmapping.levels_by_trait(ZTRAIT_SPACE_RUINS))
 								if(PLACE_DEFAULT)
 									forced_ruins[linked] = -1
-		forced_z = 0
+								if(PLACE_BELOW)
+									forced_ruins[linked] = SSmapping.get_turf_below(placed_turf)
+								if(PLACE_ISOLATED)
+									forced_ruins[linked] = SSmapping.get_isolated_ruin_z()
 
 		//Update the availible list
 		for(var/datum/map_template/ruin/R in ruins_availible)
 			if(R.cost > budget)
 				ruins_availible -= R
-
+	
 	log_world("Ruin loader finished with [budget] left to spend.")