class ChefCLI::PolicyfileServices::CleanPolicyCookbooks

def cookbooks_to_clean
  active_cbs = active_cookbooks
  all_cookbooks.inject({}) do |cb_map, (cb_name, revisions)|
    active_revs = active_cbs[cb_name] || Set.new
    inactive_revs = Set.new(revisions) - active_revs
    cb_map[cb_name] = inactive_revs unless inactive_revs.empty?
    cb_map
  end
end