restores reaction max_reqs checking code

code/modules/atmospherics/gasmixtures/gas_mixture.dm

@@ -399,7 +399,7 @@ GLOBAL_LIST_INIT(gaslist_cache, init_gaslist_cache())
 	return ""
 
 /datum/gas_mixture/react(turf/open/dump_location)
-	. = 0
+	. = NO_REACTION
 
 	reaction_results = new
 
@@ -423,6 +423,22 @@ GLOBAL_LIST_INIT(gaslist_cache, init_gaslist_cache())
 					continue reaction_loop
 			//at this point, all minimum requirements for the reaction are satisfied.
 
+			/*	currently no reactions have maximum requirements, so we can leave the checks commented out for a slight performance boost
+				PLEASE DO NOT REMOVE THIS CODE. the commenting is here only for a performance increase.
+				enabling these checks should be as easy as possible and the fact that they are disabled should be as clear as possible
+
+			var/list/max_reqs = reaction.max_requirements.Copy()
+			if((max_reqs["TEMP"] && temp > max_reqs["TEMP"]) \
+			|| (max_reqs["ENER"] && ener > max_reqs["ENER"]))
+				continue
+			max_reqs -= "TEMP"
+			max_reqs -= "ENER"
+			for(var/id in max_reqs)
+				if(cached_gases[id] && cached_gases[id][MOLES] > max_reqs[id])
+					continue reaction_loop
+			//at this point, all requirements for the reaction are satisfied. we can now react()
+			*/
+
 			. |= reaction.react(src, dump_location)
 			if (. & STOP_REACTIONS)
 				break