atom_snake.clj

; Inspired by the snakes the have gone before:
; Abhishek Reddy's snake: http://www.plt1.com/1070/even-smaller-snake/
; Mark Volkmann's snake: http://www.ociweb.com/mark/programming/ClojureSnake.html

(ns examples.atom-snake
  (:require [examples.import-static :refer :all])
  (:import [java.awt Color Dimension]
           [java.awt.event ActionListener KeyListener]
           [javax.swing JFrame JOptionPane JPanel Timer]))

(import-static java.awt.event.KeyEvent VK_LEFT VK_RIGHT VK_UP VK_DOWN)

; ----------------------------------------------------------
; functional model
; ----------------------------------------------------------
(def width 75)
(def height 50)
(def point-size 10)
(def turn-millis 75)
(def win-length 5)
(def dirs { VK_LEFT  [-1  0]
            VK_RIGHT [ 1  0]
            VK_UP    [ 0 -1]
	    VK_DOWN  [ 0  1]})

(defn add-points [& pts]
  (vec (apply map + pts)))

(defn point-to-screen-rect [pt]
  (map #(* point-size %)
       [(pt 0) (pt 1) 1 1]))

(defn create-apple []
  {:location [(rand-int width) (rand-int height)]
   :color (Color. 210 50 90)
   :type :apple})

(defn create-snake []
  {:body (list [1 1])
   :dir [1 0]
   :type :snake
   :color (Color. 15 160 70)})

(defn move [{:keys [body dir] :as snake} & grow]
  (assoc snake :body (cons (add-points (first body) dir)
			   (if grow body (butlast body)))))

(defn turn [snake newdir]
  (if newdir (assoc snake :dir newdir) snake))

(defn win? [{body :body}]
  (>= (count body) win-length))

(defn head-overlaps-body? [{[head & body] :body}]
  (contains? (set body) head))

(def lose? head-overlaps-body?)

(defn eats? [{[snake-head] :body} {apple :location}]
   (= snake-head apple))

; START: update-positions
(defn update-positions [{snake :snake, apple :apple, :as game}]
  (if (eats? snake apple)
    (merge game {:apple (create-apple) :snake (move snake :grow)})
    (merge game {:snake (move snake)})))
; END: update-positions

(defn update-direction [{snake :snake :as game} newdir]
  (merge game {:snake (turn snake newdir)}))

(defn reset-game [game]
  (merge game {:apple (create-apple) :snake (create-snake)}))

; ----------------------------------------------------------
; gui
; ----------------------------------------------------------
(defn fill-point [g pt color]
  (let [[x y width height] (point-to-screen-rect pt)]
    (.setColor g color)
    (.fillRect g x y width height)))

(defmulti paint (fn [g object & _] (:type object)))

(defmethod paint :apple [g {:keys [location color]}]
  (fill-point g location color))

(defmethod paint :snake [g {:keys [body color]}]
  (doseq [point body]
    (fill-point g point color)))

(defn game-panel [frame game]
  (proxy [JPanel ActionListener KeyListener] []
    (paintComponent [g]
      (proxy-super paintComponent g)
      (paint g (@game :snake))
      (paint g (@game :apple)))
    ; START: swap!
    (actionPerformed [e]
      (swap! game update-positions)
      (when (lose? (@game :snake))
	(swap! game reset-game)
	(JOptionPane/showMessageDialog frame "You lose!"))
    ; END: swap!
      (when (win? (@game :snake))
	(swap! game reset-game)
	(JOptionPane/showMessageDialog frame "You win!"))
      (.repaint this))
    (keyPressed [e]
      (swap! game update-direction (dirs (.getKeyCode e))))
    (getPreferredSize []
      (Dimension. (* (inc width) point-size)
		  (* (inc height) point-size)))
    (keyReleased [e])
    (keyTyped [e])))

(defn game []
  (let [game (atom (reset-game {}))
	frame (JFrame. "Snake")
	panel (game-panel frame game)
	timer (Timer. turn-millis panel)]
    (doto panel
      (.setFocusable true)
      (.addKeyListener panel))
    (doto frame
      (.add panel)
      (.pack)
      (.setVisible true))
    (.start timer)
    [game, timer]))