(ns foo
  (:require [clojure.test :refer (with-test is are run-tests)]))

(with-test
  (defn flatten-map [m kf vf]
    (into {}
      ((fn g [kv n]
         (if (map? n)
             (apply concat
               (keep (fn [[k v]] (g (conj kv k) v)) n))
             (if-let [kfkv (kf kv)]
               (if-let [vfn (vf n)]
                 [[kfkv vfn]]))))
       [] m)))

  (are [m kf vf _ r] (= (flatten-map m kf vf) r)
    {:a {:b {:c "3" :d "4"} :e "5"}} identity identity 
      -> {[:a :b :c] "3" [:a :b :d] "4" [:a :e] "5"}
    {:a {:b {:c "3" :d "4"} :e "5"}}
      #(keyword (apply str (interpose ":" (map name %))))
      read-string
      -> {:a:b:c 3 :a:b:d 4 :a:e 5}))

(with-test
  (defn deep-merge [a b]
    (reduce (fn [a [kv n]] (assoc-in a kv n))
            a
            ((fn g [kv n]
               (if (map? n)
                   (apply concat
                     (map (fn [[k v]] (g (conj kv k) v)) n))
                   [[kv n]]))
             [] b)))

  (are [a b _ r] (= (deep-merge a b) r)
    {:a {:b {:c 3 :d 4} :e 5}}
    {:a {:b {:c 6 :f 7}} :g 8}
    ->
    {:a {:b {:c 6 :d 4 :f 7} :e 5} :g 8}))

(with-test
  (defn mapf [m f & args]
    (reduce (fn [a [kv n]] (assoc-in a kv n))
            {}
            ((fn g [kv n]
               (if (map? n)
                   (apply concat
                     (keep (fn [[k v]] (g (conj kv k) v)) n))
                   (if-let [fna (apply f n args)]
                     [[kv fna]])))
             [] m)))

  (is (= (mapf {:a {:b 3 :c 4} :d 5} #(* % %))
         {:a {:b 9 :c 16} :d 25}))
  (is (= (mapf {:a {:b 3 :c 4} :d 5} #(+ (* %1 %1) %2) 1)
         {:a {:b 10 :c 17} :d 26}))
  (is (= (mapf {:a {:b 3 :c 4} :d 0} #(try (/ %2 %1) (catch Exception e)) 1)
         {:a {:b 1/3 :c 1/4}})))