Improve cleanbot ai slightly

*Multiple cleanbots will no longer attempt to clean the same tile at the same time.
*Cleanbots will now clean tiles closer to them first.

code/modules/mob/living/bot/cleanbot.dm

@@ -19,6 +19,11 @@
 	..()
 	get_targets()
 
+/mob/living/bot/cleanbot/Destroy()
+	if(target)
+		cleanbot_reserved_turfs -= target
+	return ..()
+
 /mob/living/bot/cleanbot/handleIdle()
 	if(!screwloose && !oddbutton && prob(2))
 		custom_emote(2, "makes an excited booping sound!")
@@ -65,18 +70,29 @@
 	return .
 
 /mob/living/bot/cleanbot/lookForTargets()
-	for(var/obj/effect/decal/cleanable/D in view(world.view, src)) // There was some odd code to make it start with nearest decals, it's unnecessary, this works
-		if(confirmTarget(D))
-			target = D
-			return
+	for(var/i = 0, i <= world.view, i++)
+		for(var/obj/effect/decal/cleanable/D in view(i, src))
+			if (i > 0 && get_dist(src, D) < i)
+				continue // already checked this one
+			else if(confirmTarget(D))
+				target = D
+				cleanbot_reserved_turfs += D
+				return
+
+/mob/living/bot/resetTarget()
+	cleanbot_reserved_turfs -= target
+	..()
 
 /mob/living/bot/cleanbot/confirmTarget(var/obj/effect/decal/cleanable/D)
 	if(!..())
-		return 0
+		return FALSE
+	if(D.loc in cleanbot_reserved_turfs)
+		return FALSE
 	for(var/T in target_types)
 		if(istype(D, T))
-			return 1
-	return 0
+			return TRUE
+	return FALSE
+
 
 /mob/living/bot/cleanbot/handleAdjacentTarget()
 	if(get_turf(target) == src.loc)
@@ -105,6 +121,7 @@
 			return
 		qdel(D)
 		if(D == target)
+			cleanbot_reserved_turfs -= target
 			target = null
 	busy = 0
 	update_icons()