Here we go again

code/controllers/subsystem/idlenpcpool.dm

@@ -0,0 +1,41 @@
+SUBSYSTEM_DEF(idlenpcpool)
+	name = "Idling NPC Pool"
+	flags = SS_POST_FIRE_TIMING|SS_BACKGROUND
+	priority = FIRE_PRIORITY_IDLE_NPC
+	wait = 60
+	runlevels = RUNLEVEL_GAME | RUNLEVEL_POSTGAME
+
+	var/list/currentrun = list()
+	var/static/list/idle_mobs_by_zlevel[][]
+
+/datum/controller/subsystem/idlenpcpool/stat_entry()
+	var/list/idlelist = GLOB.simple_animals[AI_IDLE]
+	var/list/zlist = GLOB.simple_animals[AI_Z_OFF]
+	..("IdleNPCS:[idlelist.len]|Z:[zlist.len]")
+
+/datum/controller/subsystem/idlenpcpool/Initialize(start_timeofday)
+	idle_mobs_by_zlevel = new /list(world.maxz,0)
+	return ..()
+
+/datum/controller/subsystem/idlenpcpool/fire(resumed = FALSE)
+	if(!resumed)
+		var/list/idlelist = GLOB.simple_animals[AI_IDLE]
+		src.currentrun = idlelist.Copy()
+
+	//cache for sanic speed (lists are references anyways)
+	var/list/currentrun = src.currentrun
+
+	while(currentrun.len)
+		var/mob/living/simple_animal/SA = currentrun[currentrun.len]
+		--currentrun.len
+		if(!SA)
+			GLOB.simple_animals[AI_IDLE] -= SA
+			continue
+
+		if(!SA.ckey)
+			if(SA.stat != DEAD)
+				SA.handle_automated_movement()
+			if(SA.stat != DEAD)
+				SA.consider_wakeup()
+		if(MC_TICK_CHECK)
+			return