(ns some-namesace.blahblah
  (:require [clojure.test :refer :all]
            [some-other-namespace.blah.test-helper :refer [assert-equal]]
            [clojure.string :as str]))

(defn- nesting-chain [expr] (re-seq #"[a-z]+|\[\]" expr))

(defn transform
  [acc [chain v]]
  (if (= (last chain) "[]")
    (update-in acc (drop-last chain) concat [v])
    ; by default, concat nil [v] will create sequences
    ; if you really want vectors instead, replace the previous line by:
    ; (update-in acc (drop-last chain) (comp (partial into []) concat) [v])
    (assoc-in acc chain v)
    ))

(defn parse-http-params
  [s]
  (->>
   (str/split s #"&")
   (map #(str/split % #"="))
   (map #(vector (nesting-chain (first %)) (second %)))
   (reduce transform {})))

(deftest test-asserts
  (let [params-str "a[b][w][y]=3&a[c]=2&a[d][]=1&a[d][]=2&x[]=1&x[]=2&x[]=3"
        expected { "a" {"b" { "w" { "y" "3" } } "c" "2" "d" ["1" "2"] } "x" ["1" "2" "3"] }]
    (assert-equal expected (parse-http-params params-str))))