Storage tanks fill levels (#23005)

# Summary

This PR adds visual fill levels for fuel, extinguisher, water, cooking
oil and lube tanks.
The cooking oil tank now is also persistent and was added to the cargo
order manifest.

Sprites by @alsoandanswer 

## Preview

<img width="404" height="472" alt="image"
src="https://github.com/user-attachments/assets/4ff4a0dd-e790-4a63-bc1a-6e198199ee7c"
/>

code/modules/cargo/items/miscellaneous.dm

@@ -26,6 +26,20 @@
 	groupable = TRUE
 	spawn_amount = 1
 
+/singleton/cargo_item/cookingoil
+	category = "miscellaneous"
+	name = "cooking oil tank"
+	supplier = "orion"
+	description = "A tank filled with cooking oil."
+	price = 450
+	items = list(
+		/obj/structure/reagent_dispensers/cookingoil
+	)
+	access = 0
+	container_type = "box"
+	groupable = TRUE
+	spawn_amount = 1
+
 /singleton/cargo_item/sculptingblock
 	category = "miscellaneous"
 	name = "sculpting block"

code/modules/cargo/random_stock/t2_uncommon.dm

@@ -331,15 +331,6 @@ STOCK_ITEM_UNCOMMON(bang, 0.5)
 	var/obj/item/gun/bang/B = pick(subtypesof(/obj/item/gun/bang))
 	new B(L)
 
-STOCK_ITEM_UNCOMMON(cookingoil, 1)
-	var/turf/T = get_turf(L)
-	if(!turf_clear(T))
-		for(var/turf/U in range(T,1))
-			if(turf_clear(U))
-				T = U
-				break
-	new /obj/structure/reagent_dispensers/cookingoil(T)
-
 STOCK_ITEM_UNCOMMON(coin, 1.3)
 	new /obj/random/coin(L)
 	if(prob(20))

code/modules/reagents/reagent_dispenser.dm

@@ -2,7 +2,7 @@
 	name = "strange dispenser"
 	desc = "What the fuck is this?"
 	icon = 'icons/obj/reagent_dispensers.dmi'
-	icon_state = "watertank"
+	icon_state = "watertank" // Mapping icon
 	density = 1
 	anchored = 0
 	maxhealth = OBJECT_HEALTH_HIGH
@@ -12,6 +12,7 @@
 	var/capacity = 1000
 	var/can_tamper = TRUE
 	var/is_leaking = FALSE
+	var/has_fill_levels = FALSE // Features base underlay and overlays for 100%, 80%, 60%, 40%, 20% fill levels
 	var/is_persistent = FALSE
 
 /obj/structure/reagent_dispensers/mechanics_hints(mob/user, distance, is_adjacent)
@@ -29,11 +30,49 @@
 
 /obj/structure/reagent_dispensers/Initialize()
 	. = ..()
+	if(has_fill_levels)
+		icon_state = "[icon_state]_underlay" // Replace mapping icon with underlay version for fill level overlay
 	create_reagents(capacity)
 	if (!possible_transfer_amounts)
 		src.verbs -= /obj/structure/reagent_dispensers/verb/set_APTFT
 	if(is_persistent)
 		SSpersistence.objectsRegisterTrack(src)
+	update_icon()
+
+/obj/structure/reagent_dispensers/update_icon()
+	if(!has_fill_levels)
+		return
+	ClearOverlays()
+
+	var/level = reagents.total_volume / capacity
+	var/fill_level_overlay = null
+
+	if(level <= 1.0)
+		fill_level_overlay = "_100"
+	if(level <= 0.8)
+		fill_level_overlay = "_80"
+	if(level <= 0.6)
+		fill_level_overlay = "_60"
+	if(level <= 0.4)
+		fill_level_overlay = "_40"
+	if(level <= 0.2)
+		fill_level_overlay = "_20"
+	if(level == 0)
+		fill_level_overlay = null
+
+	if(fill_level_overlay)
+		AddOverlays("[initial(icon_state)][fill_level_overlay]")
+	. = ..()
+
+// Debug verb, uncomment if you are in need to adjust a lot of tanks
+//	/obj/structure/reagent_dispensers/verb/adjust_regeant_total_volume()
+//		set name = "Set reagent total volume"
+//		set category = "Object"
+//		set src in view(1)
+//		var/x = tgui_input_number(usr, "Select the total reagent amount for this. ", "[src]", capacity, capacity, 0)
+//		if (x)
+//			reagents.total_volume = x
+//			update_icon()
 
 /obj/structure/reagent_dispensers/persistent_objects_get_content()
 	var/list/content = ..()
@@ -70,8 +109,8 @@
 	qdel(src)
 
 /obj/structure/reagent_dispensers/attackby(obj/item/attacking_item, mob/user)
-
 	var/obj/item/reagent_containers/RG = attacking_item
+
 	if (istype(RG))
 		if(!user.Adjacent(src)) return
 		if(RG.loc != user && !isrobot(user)) return
@@ -89,6 +128,7 @@
 				RG.standard_pour_into(user,src)
 			else
 				to_chat(user,SPAN_NOTICE("The inlet cap on \the [src] is wrenched on tight!"))
+		update_icon()
 
 	if (attacking_item.tool_behaviour == TOOL_WRENCH)
 		if(use_check(user, USE_DISALLOW_SPECIALS))
@@ -121,6 +161,7 @@
 
 	var/splash_amount = min(amount_per_transfer_from_this,60) //Hard limit of 60 per process
 	reagents.trans_to_turf(get_turf(src),splash_amount)
+	update_icon()
 
 /obj/structure/reagent_dispensers/on_death(damage, damage_flags, damage_type, armor_penetration, obj/weapon)
 	if(!should_use_health)
@@ -139,6 +180,7 @@
 	icon_state = "extinguisher_tank"
 	amount_per_transfer_from_this = 150 // Same volume as extinguisher refillers, quality of life value
 	reagents_to_add = list(/singleton/reagent/toxin/fertilizer/monoammoniumphosphate = 1000)
+	has_fill_levels = TRUE
 	is_persistent = TRUE
 
 // Tanks
@@ -148,6 +190,7 @@
 	icon_state = "watertank"
 	amount_per_transfer_from_this = 300
 	reagents_to_add = list(/singleton/reagent/water = 1000)
+	has_fill_levels = TRUE
 	is_persistent = TRUE
 
 /obj/structure/reagent_dispensers/lube
@@ -155,6 +198,7 @@
 	desc = "A tank filled with a silly amount of lube."
 	icon_state = "lubetank"
 	amount_per_transfer_from_this = 30
+	has_fill_levels = TRUE
 	reagents_to_add = list(/singleton/reagent/lube = 1000)
 
 /obj/structure/reagent_dispensers/fueltank
@@ -167,6 +211,7 @@
 	var/armed = 0
 	var/obj/item/assembly_holder/rig = null
 	reagents_to_add = list(/singleton/reagent/fuel = 1000)
+	has_fill_levels = TRUE
 	is_persistent = TRUE
 
 /obj/structure/reagent_dispensers/fueltank/feedback_hints(mob/user, distance, is_adjacent)
@@ -474,6 +519,8 @@
 	amount_per_transfer_from_this = 120
 	capacity = 1000
 	reagents_to_add = list(/singleton/reagent/nutriment/triglyceride/oil/corn = 1000)
+	has_fill_levels = TRUE
+	is_persistent = TRUE
 
 /obj/structure/reagent_dispensers/cookingoil/bullet_act(obj/projectile/hitting_projectile, def_zone, piercing_hit)
 	. = ..()