Get available fields for custom sort.

I've been working on a module to manage and create the sorts available for Solr. So far I can add, edit or delete sort types, but to add a new sort type we have to lookup the corresponding field in the Solr instance (we have to go to the Solr instance in a browser and open Schema Browser -> fields).
To make this more user friendly it would be nice to get those fields from the solr instance and load them in a dropdown box or something like that, so that the user can just select the field he is looking for.
However there doesn't seem to be any functionality to retrieve these fields, anybody got any ideas to do this?

PS:
As soon as this is done the module will be contributed.