computer_player.clj

(defn is-computer?
  [player marker]
  (= (.marker player) marker))

(defn calculate-win
  [board players depth marker]
  (let [winner (get-winner board players)]
    (if (is-computer? winner marker)
      (- 10 depth)
      (- depth 10))))

(defn best-move-and-score
  [player moves marker]
  (if (is-computer? player marker)
    (apply max-key val moves)
    (apply min-key val moves)))

(defn best-score
  [player moves marker]
  (val (best-move-and-score player moves marker)))

(defn best-move
  [player moves marker]
  (key (best-move-and-score player moves marker)))

(defn get-score
  [board players depth marker]
  (cond (win? board players) (calculate-win board players depth marker)
        (tie? board players) 0
        :else (best-score (second players) (score-moves board (switch-player players) (inc depth) marker) marker)))

(defn score-moves
  [board players depth marker]
   (let [moves (get-empty-cells board)
         player (first players)
         scores (map #(get-score (mark-cell board % (.marker player)) players depth marker) moves)]
   (zipmap moves scores)))

(defn get-minimax-move
  [board players marker]
  (let [depth 0
        player (first players)
        scored-moves (score-moves board players depth marker)]
    (best-move player scored-moves marker)))