;; GRID
(defn create-tile [position]
  {:position position
   :content nil})

(defn create-grid [[size-x size-y]]
  (mapv
    (fn [x] (mapv (fn [y] (create-tile [x y])) (range size-y)))
    (range size-x)))

(defn position-in-grid? [[pos-x pos-y] grid]
  (and
    (>= pos-x 0)
    (>= pos-y 0)
    (< pos-x (count grid))
    (< pos-y (count (grid pos-x)))))

(defn validate-position [position grid]
  (if (not (position-in-grid? position grid))
    (throw (AssertionError. (str "Invalid position " position)))))

(defn place-content [position content grid]
  (validate-position position grid)
  (assoc grid (first position)
    (assoc
      (grid (first position))
      (second position)
      {:position position :content content})))

;; ROBOTS
(defn create-robot [position state]
  (create-game-state
    (place-content position :robot (:grid state))
    (conj (:robots state) (hash-map :position position :direction [0 1]))
  )
)

(defn walk-robot [robot state]
  (let [new-pos (vec (map + (:position robot) (:direction robot)))]
    (validate-position new-pos (:grid state))
    (create-robot
      new-pos
      (create-game-state
        (place-content (:position robot) nil (:grid state))
        (remove #(= (:position robot) (:position %)) (:robots state))))))

;; STATE
(defn create-game-state [grid robots]
  {:grid grid
   :robots robots})

(as-> (create-game-state (create-grid [2 2]) []) state
  (create-robot [1 0] state)
  (do (println state "\n") state)
  (walk-robot (first (:robots state)) state)
  (do (println state "\n") state)
)