(defn lower-key [x]
  (if (or (string? x) (keyword? x))
    (-> x name .toLowerCase keyword)
    x))


(defn map-keys
  "applies f to each key of m. also to keys of m's vals and so on."
  [f m]
  (zipmap
   (map (fn [k]
          (f k))
        (keys m))
   (map (fn [v]
          (if (map? v)
            (map-keys f v)
            v))
        (vals m))))

(map-keys lower-key
             {:aBaB 123
              "CAsasas" {1 "doesn't apply to non-string non-keyword keys"
                         :yoGURt "mmMMm"
                         :notVALUES "either"}})