Item Pool and Item Stacking

I have this problem in my map (it's an RPG), What I want is for different %'s of chance to get different items, I've separated the items into these catagories: Charged, Normal, Magical, Rare, Set, And Unique.

Charged 27%
Normal 45%
Magical 20%
Rare 5%
Set 2%
Unique 1%

and then each one of these catagories is separated into 3 different levels or rarity: low, medium, high.

Low 50%
Medium 35%
High 15%

The only way i have been able to get this to work is with creating one item from a random set of items and removing item it, but as you can kinda tell it creates a lag spike.

Event: Map initialization
Conditions: None
Actions:
Set ItemClass(27,1) to Charged
Set ItemClass(27,1) to Charged
Set ItemClass(72,28) to Normal
Set ItemClass(72,28) to Normal
Set ItemClass(92,73) to Magical
Set ItemClass(92,73) to Magical
Set ItemClass(97,93) to Rare
Set ItemClass(97,93) to Rare
Set ItemClass(98) to Set
Set ItemClass(99) to Set
Set ItemClass(100) to Unqiue
Set ItemLevel(10,1) to LowCharged
Set ItemLevel(10,1) to LowCharged
Set ItemLevel(17,11) to MediumCharged
Set ItemLevel(17,11) to MediumCharged
Set ItemLevel(20,17) to HighCharged
Set ItemLevel(20,17) to HighCharged
Set ItemLevel(10,1) to LowNormal
Set ItemLevel(10,1) to LowNormal
Set ItemLevel(17,11) to MediumNormal
Set ItemLevel(17,11) to MediumNormal
Set ItemLevel(20,17) to HighNormal
Set ItemLevel(20,17) to HighNormal
Set ItemLevel(10,1) to LowMagical
Set ItemLevel(10,1) to LowMagical
Set ItemLevel(17,11) to MediumMagical
Set ItemLevel(17,11) to MediumMagical
Set ItemLevel(20,17) to HighMagical
Set ItemLevel(20,17) to HighMagical
Set LCharged(1) to Small HP Potion
Set LCharged(2) to Small MP Potion
Set LCharged(3) to Small Potion of Speed

^ you get the picture ^


Event: a unit owned by player 12 dies
Conditions: none
Actions: Create 1 ItemClass(random number 1 to 100) at position of dying unit
Remove last created Item
If/Then/Else:
If: Last created Item is equal to Charged
Then: Create 1 ItemLevel(random number 1 to 20)
If/Then/Else:
If: last created item is equal to lowcharged
Then: Create 1 LCharged(random number 1 to 20) <-- this is the final item.

Now this goes on for each class and level, my problem is that it creates a lag spike and that I need the %'s to change when your hero get's to a higher level, with this system the only way to imporve your chances in to increase the number of items dropped.

could anyone help me out to find a better system?

Ok, this one is a bit easier. What I want is when you pick up an item like a small hp potion to stack with another small hp potion you have in your inventory already.

Ok thanks guys!

The first one could be done with the itempool api.
As far as the second one I say you steal aiursrage code:
function HasItemtype takes unit whichUnit, item this returns item
local integer i = 0
local item whichItem = null
local integer itemType = GetItemTypeId(this)
if whichUnit != null then
loop
exitwhen i > 6
set whichItem = UnitItemInSlot(whichUnit, i)
if GetItemTypeId(whichItem) == itemType and whichItem != this then
return whichItem
endif
set i = i + 1
endloop
endif
return null
endfunction

function StackItem takes unit whichHero, item whichItem returns nothing
local item stack = HasItemtype(whichHero,whichItem)
local integer itemCharges = GetItemCharges(stack)
if stack != null and stack != whichItem and itemCharges > 0 then
call SetItemCharges( stack, itemCharges+ GetItemCharges(whichItem))
call RemoveItem( whichItem)
endif
endfunction
To use it you'd do
event-Unit Aquires an Item
Action
Custom script: call StackItem(GetTriggerUnit(), GetManipulatedItem())

Ok, i have a question about the itempool, how do you add itesm 2 it?

Ok, one more thing, how do I add items to the item pool, its says ID but nowhere under it does it say like item type.

itemid==itemtype, yes worldedit has a strange naming scheme.

i understand that, what i don't know is how to take an item like claws of attack and give it 10% chance 2 be dropped, when i click on ID it doesn't have anything that says item type, it says custom item value and Item level and remaining charges in item but no item type. does every item have a number ID and do i have 2 use that? and if so where can i find out hte ID's of each item?

hit ctrl-d and you should see some like I004 or whatever put that in single quotes (') and that'll do.

ok, i got that, i have the code for the items, but i don't know what thing to use it with under ID, it isn't string length or the string conversion so what do i use?