Collection of clojure utilities and macros

clojutils.clj

(defmacro first-do
 "Executes first expression of do-block and returns it's result after the rest of the body"
 [fexpr & body]
  `(let [a# ~fexpr]
     (do ~@body a#)))

; EXAMPLE:
;(first-do
;  (calculate-something 1 2 3)
;  (send-metrics "finished-calculation-of-something" 2))


(defmacro let-go
 "Like ordinary go-block but first param is symbol for channel thats returned automatically.
  same as:
  (let-go c
    ...something with c)

  ->

  (let [c (chan)]
    (go ...something with c)
    c)"
 [channel & body]
 `(let [~channel (chan)]
    (go ~@body)
    ~channel))




(defn ->uuid
  "Convert UUID-formatted string to java UUID-object"
  [s]
  (java.util.UUID/fromString s))

; EXAMPLE:
; (->uuid "123e4567-e89b-12d3-a456-426655440000")
; #"123e4567-e89b-12d3-a456-426655440000"



(defn try-catch
  "Evalute f in a try catch returning a vector with first element as possible exception and second element as evaluation result or default value. Default value defaults to nil"
  ([f] (try-catch f nil))
  ([f default]
   (try [nil (f)]
        (catch Exception e [e default]))))

(defmacro m-try-catch [body]
  `(try-catch (fn [] (~@body))))

(defmacro m-try-catch-ignore [body]
  `(second (try-catch (fn [] (~@body)))))


(def ^:private hex-chars
  (byte-array (.getBytes "0123456789abcdef" "UTF-8")))


(defn bytes->hex
  "Convert Byte Array to Hex String"
  ^String
  [^"[B" data]
  (let [len (alength data)
        ^"[B" buffer (byte-array (* 2 len))]
    (loop [i 0]
      (when (< i len)
        (let [b (aget data i)]
          (aset buffer (* 2 i) (aget hex-chars (bit-shift-right (bit-and b 0xF0) 4)))
          (aset buffer (inc (* 2 i)) (aget hex-chars (bit-and b 0x0F))))
        (recur (inc i))))
    (String. buffer "UTF-8")))


(defn mapmap-kv [f m]
  "maps hashmaps with pairs"
  (reduce-kv (fn [prev k v]
                (let [[n-k n-v] (f k v)]
                  (assoc prev n-k n-v))) {} m))

(defn mapmap [f m]
  "maps hashmaps"
  (mapmap-kv (fn [k v] (list k (f v))) m))


(defn now []
  (System/currentTimeMillis))