Got sucked in

better-version.clj

(ns email-jonas.core
  (:import (java.util Base64)))

(defn build-cipher [xs]
  (let [[frst scnd] (partition (int (/ (count xs) 2)) xs)]
    (merge (zipmap frst scnd) (zipmap scnd frst))))

(def ciphers (merge (build-cipher "abcdefghijklmnopqrstuvwxyz")
                    (build-cipher "ABCDEFGHIJKLMNOPQRSTUVWXYZ")))

(defn decode-base64 [s]
  (String. (-> (Base64/getDecoder) (.decode s))))

(defn decode-rot13 [s]
  (apply str (map #(get ciphers % %) s)))

(comment

  "From https://jonase.github.io/nil-recur/pages/about.html"
  (decode-rot13 (decode-base64 "d2JhbmYucmF5aGFxQHR6bnZ5LnBieg=="))

  )

email-jonas.clj

(ns email-jonas.core
  (:import (java.util Base64)))

(def alphabet "abcdefghijklmnopqrstuvwxyz")

(defn shiftable? [c]
  ((set alphabet) c))

(defn shift [n direction c]
  (if (not (shiftable? c))
    c
    (let [normalize (fn [i] (mod (- i (int \a)) (count alphabet)))
          letter-idx (normalize (Math/abs (direction n (int c))))]
      (get alphabet letter-idx))))

(defn decode-base64 [s]
  (String. (-> (Base64/getDecoder) (.decode s))))

(defn decode-rot13 [s]
  (apply str (map (partial shift 13 -) s)))

(comment

  "From https://jonase.github.io/nil-recur/pages/about.html"
  (decode-rot13 (decode-base64 "d2JhbmYucmF5aGFxQHR6bnZ5LnBieg=="))

  )