Simple indent parser in Clojure

gistfile1.clj

(ns analyze  (:require
   [clojure.string :refer [split starts-with? trim]]
   [clojure.core :refer [tree-seq re-find]]))

(defn line-param [line]
  (trim (str (second (re-find #"\s*(.*?):" (str line))))))

(defn line-value [line]
  (trim (str (second (re-find #".*:(.*)" (str line))))))

(defn whitespace-start [s]
  (if (nil? s)
    0
    (loop [sum 0
           s s]
      (if (not= (first s) \space)
        sum
        (recur (inc sum) (rest s))))))

(defn ->branch [line child-obj]
  {(line-param line) child-obj})

(defn ->leaf [line]
  {(line-param line) (line-value line)})

(defn partition-by-n [lines n] (partition-by #(= (whitespace-start %) n) lines))

(defn ->desc [lines]
  (if (< (whitespace-start (first lines)) (whitespace-start (second lines)))
    (second (partition-by-n lines (whitespace-start (first lines))))
    nil))

(defn ->tree
  ([lines]
   (->tree lines []))
  ([lines obj]
    (loop [lines (filter #(not-empty %) lines)
          obj obj]
    (if (empty? lines)
      obj
      (recur
       (drop (max 1 (inc (count (->desc lines)))) lines)
       (merge obj (let [node (first lines)]
                    (if-let [children (->desc lines)]
                      (->branch node (->tree children {}))
                      (->leaf node)))))))))


(def lines "
Param 1:
   Param 2: 
      Param 3: value3
      Param 4: 12
         Param 9: 12
Param 2:
 Param 3: value5
Param 4: value6
")

(clojure.pprint/pprint (->tree (split lines #"\n")))
[{"Param 1"
  {"Param 2" {"Param 3" "value3", "Param 4" {"Param 9" "12"}}}}
 {"Param 2" {"Param 3" "value5"}}
 {"Param 4" "value6"}]
nil