minimax.clj

(defn- minimax-square 
  [{:keys [board current-player opposing-player player-turn square] :as params}]
    (let [new-board (board/take-square board player-turn square)]
      (cond
        (board/winner? new-board current-player) 10
        (board/winner? new-board opposing-player) -10
        (board/tie?    new-board current-player opposing-player) 0
        :else (let [next-player (next-player current-player opposing-player player-turn)
                    next-board-states (board/open-squares new-board)]
                  (minimax-for-open-postions 
                    (assoc params :board new-board :player-turn next-player) next-board-states)))))

(defn- minimax-for-open-postions [{:keys [current-player player-turn] :as params} open-squares]
   (let [scores (map #(minimax-square (assoc params :square %)) open-squares)]
     (if (= player-turn current-player)
       (apply max scores)
       (apply min scores))))