Node ID - Loading Hierarchical Data

CREATE TABLE #Source
(
Id int identity(1,1)
,categoryint
,Leaf_Node_code varchar(10) --
,Level1_Name varchar(20)
,Level2_Name varchar(20)

[Code] ....

Here category 1 has 3 levels ,

category 2 has 4 levels ,
category 3 has 5 levels ,

Below is the target table, here Leaf_Node_code should populate to only for leaf nodes for each category .. Need to populate Node_id with hierarchical data

I am unable frame a sql query to handle different levels , in future #Source may have more levels .

How to handle multiple hierarchy levels .. here only leaf node should have Leaf_Node_code

CREATE TABLE TARGET_TABLE
(
ID INT IDENTITY(1,1) primary key
,Node_id HIERARCHYID
,category int
,Parent_id int references TARGET_TABLE(id)
,Leaf_Node_code varchar(10)
,Namevarchar(20)
)

Here is the expected output:

IDcategoryParent_idLeaf_Node_codeName Node_id
11NULLNULLWorld
211NULLAsia
312101India
42NULLNULLa
524NULLaa
625NULLaaa
726102aaaa
83NULLNULLb
938NULLbb
1039NULLbbb
11310NULLbbbb
12311103bbbb