Atmos init speedup, saves 4 seconds (#69697)

* Micro optimizes ssair's turf init, saving 2 seconds

Most of this is making existing operations do more legwork, or cheaper.
I did add cycle checking to ONLY init turf linking, which required
creating a new proc.
Did some horrible horrible things in said proc to save like 0.8 seconds.
I think it was worth it.

code/controllers/subsystem/air.dm

@@ -36,6 +36,9 @@ SUBSYSTEM_DEF(air)
 	var/list/gas_reactions = list()
 	var/list/atmos_gen
 	var/list/planetary = list() //Lets cache static planetary mixes
+	/// List of gas string -> canonical gas mixture
+	var/list/strings_to_mix = list()
+
 
 	//Special functions lists
 	var/list/turf/active_super_conductivity = list()
@@ -521,7 +524,7 @@ SUBSYSTEM_DEF(air)
 /datum/controller/subsystem/air/proc/setup_allturfs()
 	var/list/turfs_to_init = block(locate(1, 1, 1), locate(world.maxx, world.maxy, world.maxz))
 	var/list/active_turfs = src.active_turfs
-	var/times_fired = ++src.times_fired
+	times_fired++
 
 	// Clear active turfs - faster than removing every single turf in the world
 	// one-by-one, and Initalize_Atmos only ever adds `src` back in.
@@ -531,13 +534,16 @@ SUBSYSTEM_DEF(air)
 		active.remove_atom_colour(TEMPORARY_COLOUR_PRIORITY, COLOR_VIBRANT_LIME)
 	#endif
 	active_turfs.Cut()
+	var/time = 0
 
-	for(var/thing in turfs_to_init)
-		var/turf/T = thing
-		if (T.blocks_air)
+	for(var/turf/T as anything in turfs_to_init)
+		if (!T.init_air)
 			continue
-		T.Initalize_Atmos(times_fired)
-		CHECK_TICK
+		// We pass the tick as the current step so if we sleep the step changes
+		// This way we can make setting up adjacent turfs O(n) rather then O(n^2)
+		T.Initalize_Atmos(time)
+		if(CHECK_TICK)
+			time++
 
 	if(active_turfs.len)
 		var/starting_ats = active_turfs.len
@@ -561,8 +567,8 @@ SUBSYSTEM_DEF(air)
 
 			active_turfs += new_turfs_to_check
 			turfs_to_check = new_turfs_to_check
-
 		while (turfs_to_check.len)
+
 		var/ending_ats = active_turfs.len
 		for(var/thing in excited_groups)
 			var/datum/excited_group/EG = thing
@@ -663,6 +669,38 @@ GLOBAL_LIST_EMPTY(colored_images)
 		var/datum/atmosphere/atmostype = T
 		atmos_gen[initial(atmostype.id)] = new atmostype
 
+/// Takes a gas string, returns the matching mutable gas_mixture
+/datum/controller/subsystem/air/proc/parse_gas_string(gas_string)
+	var/datum/gas_mixture/cached = strings_to_mix[gas_string]
+	if(cached)
+		if(istype(cached, /datum/gas_mixture/immutable))
+			return cached
+		return cached.copy()
+
+	var/datum/gas_mixture/canonical_mix = new()
+	// We set here so any future key changes don't fuck us
+	strings_to_mix[gas_string] = canonical_mix
+	gas_string = preprocess_gas_string(gas_string)
+
+	var/list/gases = canonical_mix.gases
+	var/list/gas = params2list(gas_string)
+	if(gas["TEMP"])
+		canonical_mix.temperature = text2num(gas["TEMP"])
+		canonical_mix.temperature_archived = canonical_mix.temperature
+		gas -= "TEMP"
+	else // if we do not have a temp in the new gas mix lets assume room temp.
+		canonical_mix.temperature = T20C
+	for(var/id in gas)
+		var/path = id
+		if(!ispath(path))
+			path = gas_id2path(path) //a lot of these strings can't have embedded expressions (especially for mappers), so support for IDs needs to stick around
+		ADD_GAS(path, gases)
+		gases[path][MOLES] = text2num(gas[id])
+
+	if(istype(canonical_mix, /datum/gas_mixture/immutable))
+		return canonical_mix
+	return canonical_mix.copy()
+
 /datum/controller/subsystem/air/proc/preprocess_gas_string(gas_string)
 	if(!atmos_gen)
 		generate_atmos()