pick_weight over pickweight (#6760)

# About the pull request

Removes `pickweight` and switches over to `pick_weight`. The only
difference is that `pickweight` treated weight 0 as weight 1, and
`pick_weight` does not. Only `utility_closets` and `flow` had 0-weight
entries, and I corrected those.

Updates `pick_weight` to TG's version, which fixes a statistical error:
tgstation/tgstation#71271
tgstation/tgstation#71273

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# Explain why it's good for the game

Less redundant code. More statistical accuracy.
# Testing Photographs and Procedure
Boots.


# Changelog
:cl:
code: Fixed and refactored probability weighting for pick_weight
/:cl:

code/__HELPERS/_lists.dm

@@ -128,17 +128,23 @@
  * You should only pass integers in.
  */
 /proc/pick_weight(list/list_to_pick)
+	if(length(list_to_pick) == 0)
+		return null
+
 	var/total = 0
-	var/item
-	for(item in list_to_pick)
+	for(var/item in list_to_pick)
 		if(!list_to_pick[item])
 			list_to_pick[item] = 0
 		total += list_to_pick[item]
 
-	total = rand(0, total)
-	for(item in list_to_pick)
-		total -= list_to_pick[item]
-		if(total <= 0 && list_to_pick[item])
+	total = rand(1, total)
+	for(var/item in list_to_pick)
+		var/item_weight = list_to_pick[item]
+		if(item_weight == 0)
+			continue
+
+		total -= item_weight
+		if(total <= 0)
 			return item
 
 	return null

code/__HELPERS/lists.dm

@@ -87,22 +87,6 @@
 		result = first ^ second
 	return result
 
-//Pretends to pick an element based on its weight but really just seems to pick a random element.
-/proc/pickweight(list/L)
-	var/total = 0
-	var/item
-	for (item in L)
-		if (!L[item])
-			L[item] = 1
-		total += L[item]
-
-	total = rand(1, total)
-	for (item in L)
-		total -=L [item]
-		if (total <= 0)
-			return item
-	return null
-
 /// Pick a random element from the list and remove it from the list.
 /proc/pick_n_take(list/L)
 	RETURN_TYPE(L[_].type)

code/game/machinery/computer/arcade.dm

@@ -123,7 +123,7 @@
 			src.temp = "[src.enemy_name] has fallen! Rejoice!"
 
 			if(!length(contents))
-				var/prizeselect = pickweight(prizes)
+				var/prizeselect = pick_weight(prizes)
 				new prizeselect(src.loc)
 
 				if(istype(prizeselect, /obj/item/toy/gun)) //Ammo comes with the gun
@@ -176,5 +176,5 @@
 		if(2)
 			num_of_prizes = rand(0,2)
 	for(num_of_prizes; num_of_prizes > 0; num_of_prizes--)
-		empprize = pickweight(prizes)
+		empprize = pick_weight(prizes)
 		new empprize(src.loc)

code/game/objects/structures/crates_lockers/closets/utility_closets.dm

@@ -23,7 +23,7 @@
 	. = ..()
 
 #ifndef UNIT_TESTS
-	switch (pickweight(list("small" = 55, "aid" = 25, "tank" = 10, "both" = 10, "nothing" = 0, "delete" = 0)))
+	switch (pick_weight(list("small" = 55, "aid" = 25, "tank" = 10, "both" = 10, "nothing" = 1, "delete" = 1)))
 #else
 	var/test = "both"
 	switch (test) // We don't want randomness in tests

code/game/supplyshuttle.dm

@@ -532,7 +532,7 @@ GLOBAL_DATUM_INIT(supply_controller, /datum/controller/supply, new())
 	for(var/datum/supply_packs_asrs/crate in cratelist)
 		var/weight = (floor(10000/crate.cost))
 		weighted_crate_list[crate] = weight
-	return pickweight(weighted_crate_list)
+	return pick_weight(weighted_crate_list)
 
 //To stop things being sent to centcomm which should not be sent to centcomm. Recursively checks for these types.
 /datum/controller/supply/proc/forbidden_atoms_check(atom/A)

code/modules/nightmare/nmnodes/flow.dm

@@ -67,15 +67,14 @@
 	if(!.) return
 	var/list/datum/nmnode/pickables = choices.Copy()
 	for(var/datum/nmnode/node as anything in pickables)
-		if(isnum(node.raw["weight"]))
-			pickables[node] = node.raw["weight"]
+		pickables[node] = isnum(node.raw["weight"]) ? node.raw["weight"] : 1
 	var/list/datum/nmnode/picked = list()
 	var/remaining = src.amount
 #if defined(UNIT_TESTS)
 	remaining = length(pickables) // Force all to be picked for testing (this could potentially make false positives though)
 #endif
 	while(length(pickables) && remaining > 0)
-		var/datum/nmnode/node = pickweight(pickables)
+		var/datum/nmnode/node = pick_weight(pickables)
 		remaining--
 		pickables -= node
 		picked += node