Cur in Dev: Wp 2.3 Folding Cat List (I’m Stuck!)

I have a working 2.3 Folding Category List which I have created, only problem I have now is finding out what the current category is for the viewers context.

I’ve looked through the function reference, but can’t locate what I am after. Can anybody please help?

I need:

1. Are we looking at a single category, if so which one?
2. Are we looking at a single post, if so need array of categories associated with that post (I can then prioritise and display most relevant)
3. Should categories be expanded in any other context?
4. If above not found just display all parent cats.

If i hard code a category (e.g. 13) then child categories of 13 are shown correctly, just need to remove that hard coding.

Thanks for any help!

Tim