Swing JPanel for our Reversi Game

reversi-swing-panel.clj

(defn popup [frame msg]
  "Displays a popup containing the specified message."
  (JOptionPane/showMessageDialog frame msg))

(defn announce-winner [frame board]
  "Displays a popup containing the winner of the game."
  (let [p (winner board)]
    (cond
      (= p :w) (popup frame "White Wins!")
      (= p :b) (popup frame "Black Wins!")
      :else
      (popup frame "It's a tie!"))))

(defn reversi-panel [frame board piece]
  "Builds a JPanel to represent our Reversi game board. The panel accepts
  mouse events to place pieces on the board.

  board and piece should both be atoms."
  (let [game-over (atom false)]
    (proxy [JPanel MouseListener] []
      (paintComponent [g] ; overriding JPanel's paintComponent method
        (proxy-super paintComponent g) ; call paintComponent on the JPanel
        (draw-board g @board @piece)) ; draw our board
      (getPreferredSize [] ; defines the size of our game board
        (Dimension. board-size (+ board-size footer-height)))
      (mouseClicked [e] ; when the user clicks the mouse
        (let [rc (parse-mouse-pos (.getX e) (.getY e))] ; converts the mouse position into row-column coords
          (if (not (move-valid? @board @piece rc))
            (popup frame "Invalid move") ; the user clicked outside the main playing area or on a square with a piece
            (do ; the user clicked in an empty square
              (swap! board #(place-piece % @piece rc)) ; play the piece and update the board
              (.repaint this)
              (cond
                (game-over? @board) (do
                                      (announce-winner frame @board)
                                      (reset! game-over true))
                (empty? (take 1 (valid-moves @board (opposite-piece @piece)))) (popup frame "Still your turn!")
                :else (do
                        (swap! piece opposite-piece)
                        (.repaint this))))))) ;; we've switched players, so let's redraw to update the active player text
      (mouseReleased [e]) ; we're not doing anything for this event
      (mousePressed [e]) ; we're not doing anything for this event
      (mouseEntered [e]) ; we're not doing anything for this event
      (mouseExited [e])))) ; we're not doing anything for this event