asterisk users - Jun 2006 - Call accounting where calls cross charge zones (code fragment request)

Greetings list,

Before I go and write something from scratch, are there any kind souls here
who already have a nice code fragment that works our charging for calls
split across charging zones?

There are essentially 4 possibilities for a call:
1) call is completely within one zone, so it's nice and simple.
2) call starts in peak and finishes in the immediately following cheap zone.
3) call starts in cheap and finishes in the immediately following peak zone.
4) call is ridiculously long and completely encompasses one or more zones
(very unlikely, but probably should be able to handle it nonetheless).

I'm in the process of writing a billing module that works with
asterisk's
own CDRs (or CDRs provided by an upstream provider) and doesn't use any
AGIs, etc.. A couple of quick questions:
1) does something like this already exist?
2) if not, would it be of any interest to fellow list readers?

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
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