(ns test.core)

(def asym-hobbit-body-parts
  [{:name "head" :size 3}
   {:name "left-eye" :size 1}
   {:name "left-ear" :size 1}
   {:name "mouth" :size 1}
   {:name "nose" :size 1}
   {:name "neck" :size 2}
   {:name "left-shoulder" :size 3}
   {:name "left-upper-arm" :size 3}
   {:name "chest" :size 10}
   {:name "back" :size 10}
   {:name "left-forearm" :size 3}
   {:name "abdomen" :size 6}
   {:name "left-kidney" :size 1}
   {:name "left-hand" :size 2}
   {:name "left-knee" :size 2}
   {:name "left-thigh" :size 4}
   {:name "left-lower-leg" :size 3}
   {:name "left-achilles" :size 1}
   {:name "left-foot" :size 2}])

(defn matching-part
  [part]
  {:name (clojure.string/replace (:name part) #"^left-" "right-")
   :size (:size part)})

(defn expand-body-parts
  [expand-fn asym-body-parts]
  (reduce expand-fn [] asym-body-parts))

(defn expand-fn
  [final-body-parts part]
  (into final-body-parts (set [part (matching-part part)])))

(defn hit
  [hobbit]
  (let [total-size (reduce + (map :size hobbit))
        target-size (rand total-size)]
    (loop [[part & remaining] hobbit
           accumulated-size (:size part)]
      (if (nil? part)
        nil
        (if (> accumulated-size target-size)
          part
          (recur remaining (+ accumulated-size (:size (first remaining)))))))))

(defn main
  []
  (let [hobbit (expand-body-parts expand-fn asym-hobbit-body-parts)]
    (println (hit hobbit))))

(main)