Replace last empty tank with a single full tank on recharge (#4)

init.lua

@@ -57,9 +57,14 @@ local function recharge_airtank(itemstack, user, pointed_thing, full_item)
 			itemstack:set_wear(0)
 		else
 			local inv = user:get_inventory()
-			local leftover = inv:add_item("main", full_item)
-			if leftover:get_count() == 0 then
-				itemstack:set_count(itemstack:get_count()-1)
+
+			if itemstack:get_count() == 1 then
+				itemstack = ItemStack(full_item) -- replace with new stack containing one full tank
+			else
+				local leftover = inv:add_item("main", full_item)
+				if leftover:get_count() == 0 then
+					itemstack:take_item(1)
+				end
 			end
 		end
 		minetest.sound_play("airtanks_compressor", {pos = pointed_thing.under, gain = 0.5})
@@ -247,4 +252,5 @@ local function player_event_handler(player, eventname)
 	return false
 end
 
-minetest.register_playerevent(player_event_handler)
+minetest.register_playerevent(player_event_handler)
+