pw-classification.clj

(defn length-between? [x y]
  (fn [password] (<= x (count password) y)))

(def alpha-only? (partial re-matches #"^\p{Alpha}*$"))
(def digit-only? (partial re-matches #"^\p{Digit}*$"))
(def alpha-numeric? (partial re-matches #"^\p{Alnum}*$"))
(def special-char? (partial re-find #"[^\p{Alnum}]"))

(def classifiers {:weak   [(length-between? 0 5) 
                           (some-fn alpha-only? digit-only?)]
                  :medium [(length-between? 5 8)
                           alpha-numeric?]
                  :strong [(length-between? 8 ##Inf)
                           special-char?]})

(defn classifies? [password]
  (fn [[classifier predicates]]
    (let [pred (apply every-pred predicates)]
      (when (pred password)
        classifier))))

(defn classify [password]
  (or (->> classifiers
           (keep (classifies? password))
           first)
      :unknown))

(classify "abc")