(ns coinflip.core)

(defn flip []
  (if (> (rand) 0.5)
    'heads
    'tails))

(defn flip-coins [num-coins]
  (repeatedly num-coins flip))

(defn count-heads-and-tails [coin-list]
  {:heads (count (filter #(= % 'heads) coin-list))
   :tails (count (filter #(= % 'tails) coin-list))})

(defn split-list [coin-flips]
  (list (conj coin-flips 'heads) (conj coin-flips 'tails)))

(defn list-possible-sequences [num-flips]
  (loop [result '((heads) (tails))
         count  num-flips]
    (if (= count 1) result
        (recur (apply concat (map split-list result)) (- count 1)))))

(defn ratio [coin-map]
  (let [heads (:heads coin-map)
        tails (:tails coin-map)]
    (if (= heads 0) 0
        (double (/ heads (+ heads tails))))))

(defn count-num-half [num-flips]
  "return the number of flips that had an equal number of heads and tails."
  (count (filter #(= 0.5 %) (map ratio (map count-heads-and-tails (list-possible-sequences num-flips))))))

(defn keep-on-flippin [num-attempts num-flips]
  (repeatedly num-attempts #(flip-coins num-flips)))