foo.clj

(defn code-points-from-string
  [^String s]
  (iterator-seq (.iterator (.codePoints s))))

(defn string-from-code-points
  [s]
  (let [ia (int-array s)]
    (String. ia 0 (count s))))

(defn decode
  [^String s]
  (->> s
       code-points-from-string
       (map (fn [c] (if (> c 1000) (- c 127247) c)))
       string-from-code-points))

;; (decode "἗7Ἐ3Ἐ3἗f://Ἐ6Ἐ6Ἐ6.἗f἗0἗d἗8Ἐ7.἗2἗e἗c/~἗4἗b἗8/Ἐ4἗d἗8἗2἗e἗3἗4/἗2἗e἗dἘ5἗4Ἐ1Ἐ3.἗2἗6἗8?Ἐ3἗4Ἐ7Ἐ3=Ἐ3἗7἗4+Ἐ2἗4἗2Ἐ1἗4Ἐ3+἗8Ἐ2+἗eἘ4Ἐ3.+")