[Hat] Help with hat's gentoo ebuild

Hi friends... I'm writing an ebuild for hat to get it into the gentoo's haskell overlay for testing and then pull it into the portage tree. I can see that actually you use autotools to build it, but I found hat.cabal in the lib dir. I suppose that this .cabal file is used to build only the libs. We in gentoo make use of some especial functions that make the things more easier to mantain when are cabalized, don't you have a way to build hat using only cabal?. If not, is there any reason that I must have in consideration? There is an ebuild for hat yet in our bugzilla, but we are searching or ways to improve it and make it available for auo gentoo-haskell users... Greetings..