(defvar key-left 65361) ;; macroquad input code
(defvar key-up 65362)
(defvar key-right 65363)
(defvar key-down 65364)

(defvar gameover ())
(defvar tile-size (list 18.0 24.0))
(defvar subtile-width 5.0)
(defvar subtile-height 7.0)

(defvar player-direction ())
(defvar player-body (list (list 3 2)))
(defvar frame-timer-duration 0.3)
(defvar frame-timer 0.0)
(defvar fruit-tile (list 4 5))


(defun is-tile-equal? (pos1 pos2)
  (and (== (car pos1) (car pos2)) (== (cadr pos1) (cadr pos2)))
  )

(defun sum-pos (pos1 pos2)
  (list (+ (car pos1) (car pos2)) (+ (cadr pos1) (cadr pos2)))
  )

(defun tile-to-pos (tile)
  (list (* (car tile) (car tile-size)) (* (cadr tile) (cadr tile-size)))
  )

(defun draw-subtile (tile subtile)
  (defvar offset (tile-to-pos tile))
  (mq-draw-rectangle (+ (car offset) (+ (* subtile-width (car subtile)) (car subtile))) (+ (cadr offset) (+ (* subtile-height (cadr subtile)) (cadr subtile))) subtile-width subtile-height)
  )

(defun draw-fruit (tile)
  (draw-subtile tile (list 1 0))
  (draw-subtile tile (list 2 1))
  (draw-subtile tile (list 1 2))
  (draw-subtile tile (list 0 1))
  )

(defun draw-horizontal-line (tile)
  (draw-subtile tile (list 0 1))
  (draw-subtile tile (list 1 1))
  (draw-subtile tile (list 2 1))
  )

(defun draw-vertical-line (tile)
  (draw-subtile tile (list 1 0))
  (draw-subtile tile (list 1 1))
  (draw-subtile tile (list 1 2))
  )

(defun draw-corner-tl (tile)
  (draw-subtile tile (list 1 1))
  (draw-subtile tile (list 2 1))
  (draw-subtile tile (list 1 2))
  )

(defun draw-corner-tr (tile)
  (draw-subtile tile (list 1 1))
  (draw-subtile tile (list 0 1))
  (draw-subtile tile (list 1 2))
  )

(defun draw-corner-bl (tile)
  (draw-subtile tile (list 1 1))
  (draw-subtile tile (list 1 0))
  (draw-subtile tile (list 2 1))
  )

(defun draw-corner-br (tile)
  (draw-subtile tile (list 1 1))
  (draw-subtile tile (list 1 0))
  (draw-subtile tile (list 0 1))
  )

(defun draw-snake-tile (tile)
  (defvar offset (tile-to-pos tile))
  (mq-draw-rectangle (car offset) (cadr offset) (car tile-size) (cadr tile-size) 0.4)
  (draw-subtile tile (list 0 0))
  (draw-subtile tile (list 1 0))
  (draw-subtile tile (list 2 0))
  (draw-subtile tile (list 0 1))
  (draw-subtile tile (list 1 1))
  (draw-subtile tile (list 2 1))
  (draw-subtile tile (list 0 2))
  (draw-subtile tile (list 1 2))
  (draw-subtile tile (list 2 2))
  )

(defun process-input ()
  (if (mq-is-key-pressed key-left)
      (setq player-direction key-left))
  (if (mq-is-key-pressed key-right)
      (setq player-direction key-right))
  (if (mq-is-key-pressed key-up)
      (setq player-direction key-up))
  (if (mq-is-key-pressed key-down)
      (setq player-direction key-down))
  )

(defun move-player-body (dir)
  (setq player-body (move-player-body-aux player-body (sum-pos (car player-body) dir)))
  )

(defun move-player-body-aux (body pos)
  (if (not (null (cdr body)))
      (cons pos (move-player-body-aux (cdr body) (car body)))
    (cons pos ()))
  )

(defun push-new-tile ()
  (setq player-body (push-new-tile-aux player-body))
  )

(defun push-new-tile-aux (body)
  (if (null (cdr body))
      (list (car body) (car body))
    (cons (car body) (push-new-tile-aux (cdr body)))
    ))

(defun check-collision-self ()
  (if (null (cdr player-body))
      ()
    (check-collision-self-aux (cdr player-body) (car player-body)))
  )

(defun check-collision-self-aux (body pos)
  (if (is-tile-equal? (car body) pos)
      1
    (if (null (cdr body))
	()
      (check-collision-self-aux (cdr body) pos))
    )
  )

(defun process-frame ()
  ;; Set frame timer to 0 (game is running at 60 FPS)
  (setq frame-timer 0.0)
  
  ;; Move player
  (if (== player-direction key-left)
      (move-player-body (list -1 0))
    )

  (if (== player-direction key-up)
      (move-player-body (list 0 -1))
    )

  (if (== player-direction key-right)
      (move-player-body (list 1 0))
    )

  (if (== player-direction key-down)
      (move-player-body (list 0 1))
    )

  ;; Check collision with self
  (if (check-collision-self)
      (setq gameover 1))
  

  ;; Check collision border
  (if (or (<= (car (car player-body)) 2)
	  (>= (car (car player-body)) 31)
	  (<= (cadr (car player-body)) 1)
	  (>= (cadr (car player-body)) 22))
      (setq gameover 1))
  
  ;; Check collision with fruit
  (if (is-tile-equal? (car player-body) fruit-tile)
      (begin
       (push-new-tile)
       (setq fruit-tile (list (randi-range 3 30) (randi-range 2 21)))))
  )


(defun update (dt)
  (process-input)

  (setq frame-timer (+ frame-timer dt))
  (if (and (not gameover) (> frame-timer frame-timer-duration))
      (process-frame))

  
  )


(defun draw ()
  (mapcar (lambda (tile)
	    (draw-snake-tile tile))
	  player-body)

  (mapcar (lambda (i)
	    (draw-vertical-line (list 2 i))
	    (draw-vertical-line (list 31 i)))
	  (range 2 22))

  (mapcar (lambda (i)
	    (draw-horizontal-line (list i 1))
	    (draw-horizontal-line (list i 22)))
	  (range 3 31))

  (draw-corner-tl (list 2 1))
  (draw-corner-tr (list 31 1))
  (draw-corner-bl (list 2 22))
  (draw-corner-br (list 31 22))

  (draw-fruit fruit-tile)
  )