(defmacro restartable (&body body)
  "Helper macro since we use continue restarts a lot 
   (remember to hit C in slime or pick the restart so errors don't kill the app"
  `(restart-case
       (progn ,@body)
     (continue () :report "Continue")))

(defun make-2d-array (h w contents)
  (let ((arr (make-array h)))
    (do ((i 0 (incf i))
	 (rest-list contents (rest rest-list)))
	((eql i h)) 
      (setf (aref arr i) (make-array w :initial-contents (car rest-list))))
    arr))

(defparameter *n* (make-array 3 :initial-contents '(0 0 1)))
(defparameter *v* (make-2d-array 3 3 '((0 0.5 0) (0.5 -0.5 0.0) (-0.5 -0.5 0.0))))
(defparameter *faces* (make-2d-array 1 3 '((0 1 2))))

(defparameter *start-time* (wall-time))

(defparameter *last-time* nil)
(defparameter *num-frames* 0)

;;(defparameter *t1* '( (-0.5 -0.5 0) (0 0.5 0) (0.5 -0.5 0)))

(defun get-vertecies (faces) 
  (loop for i from 0 to (1- (length faces)) collecting (aref *v* (aref faces i))))

(let ((time-units (/ 1.0 internal-time-units-per-second)))
  (defun wall-time (&key (offset 0))
    (+ (* (get-internal-real-time) time-units)
       offset)))


(defun shift-color (time) 
  (values 
   ;;; red
   (/ (+ (* (sin (+ (* 0.3 time) 0)) 127) 128) 255)
   ;;; green
   (/ (+ (* (sin (+ (* 0.3 time) (* 2/3 PI))) 127 ) 128) 255)
   ;;; blue
   (/ (+ (* (sin (+ (* 0.3 time) (* 4/3 PI))) 127) 128) 255)))


(defun make-rotation-matrix (xa ya za) 
  (let ((sxa (sin xa))
	(cxa (cos xa))
	(sya (sin ya))
	(cya (cos ya))
	(sza (sin za))
	(cza (cos za)))
    (make-array '(3 3) :initial-contents (list (list (* cya cza) (+ (- (* cxa sza)) (* sxa sya cza)) (+ (* sxa sza) (* cxa sya cza)))
					   (list (* cya sza) (+ (* cxa cza) (* sxa sya sza)) (+ (- (* sxa cza)) (* cxa sya sza)))
					   (list (- sya) (* sxa cya) (* cxa cya))))))
					   
(defun rotate* (m v)
  (let ((result (make-array 3 :initial-element 0)))
    (dotimes (x 3)
      (dotimes (y 3)
	(incf (aref result x) (* (aref v y) (aref m x y)))))
    result))
	

(defun rotate-vertex-2d (v rM)
  v)
 ;; (let ((result (lm:* rM (lm:vector (first v) (second v)))))
 ;;   (list (lm:elt result 0) (lm:elt result 1))))
 
;; (let* ((x (first v))
;;	 (y (second v))
;;	 (theta (atan (if (eql 0 x) 1000000 (/ y x))))
;;	 (hyp (sqrt (+ (* x x) (* y y)))))
 ;;   (list (/ (cos (+ theta time)) hyp) (/ (sin (+ theta time)) hyp) (third v))))
;    (list (+ (first v) (/ (sin time) 2)) (+ (second v) (/ (cos time) 2))   (third v)))

(defun rotate-triangle (tri time)
  (list 
   (rotate* (make-rotation-matrix 0 0 time) (first tri))
   (rotate* (make-rotation-matrix 0 0 time) (second tri))
   (rotate* (make-rotation-matrix 0 0 time) (third tri))))
;  (let* ((angle (/ time 1000))
;	 (cos-a (cos angle))
;	 (sin-a (sin angle))
;	 (rM nil)) ;lm:make-matrix 2 2 :initial-elements 
;		;	     '(cos-a sin-a
;		;	       (- sin-a) cos-a))))
 ;   (list (append (rotate-vertex-2d (first tri) rM) '((third (firt tri))))
;	  (append (rotate-vertex-2d (second tri) rM) '((third (second tri))))
;	  (append (rotate-vertex-2d (third tri) rM) (third (third tri))))))
;

(defun draw ()
  "draw a frame"
  (let* ((time (- (wall-time) *start-time*))
	(t1 (rotate-triangle (get-vertecies (aref *faces* 0)) time)))
      (gl:clear :color-buffer-bit)
  ;;; draw a triangle
      (gl:with-primitive :triangles
	(multiple-value-bind (red green blue) (shift-color time)
	  (gl:color red green blue))
	(let ((v (first t1)))
	  (gl:vertex (aref v 0) (aref v 1) (aref v 2)))

	(multiple-value-bind (green blue red) (shift-color time)
	  (gl:color red green blue))
	(let ((v (second t1)))
	  (gl:vertex (aref v 0) (aref v 1) (aref v 2)))

	(multiple-value-bind (blue green red) (shift-color time)
	  (gl:color red green blue))
	(let ((v (third t1)))
	  (gl:vertex (aref v 0) (aref v 1) (aref v 2))))

    ;; finish the frame
    (gl:flush)
    (sdl:update-display)
    (incf *num-frames*)
    (if (not (eql (floor *last-time*) (floor time)))
	(let* ((short-interval (- time *last-time* ))
	       (long-interval time)
	       (short-fps (floor (if (zerop short-interval) 0 (/ 1 short-interval))))
	       (long-fps (floor (if (zerop long-interval) 0  (/ *num-frames* long-interval)))))
	       
	  (format t "FPS since last:~a since start:~a~%" short-fps long-fps)))
  
  (setf *last-time* time)))


(defun init () 
  (setf *start-time* (wall-time))
  (setf *num-frames* 0)
  (setf *last-time* 0)
)

(defun main-loop () 
  (init)
  (sdl:with-init ()
    (sdl:window 320 240 :flags sdl:sdl-opengl)
    ;; cl-opengl needs platform specific support to be able to load GL
    ;; extensions, so we need to tell it how to do so in lispbuilder-sdl
    (setf cl-opengl-bindings:*gl-get-proc-address* #'sdl-cffi::sdl-gl-get-proc-address)
    (sdl:with-events () 
      (:quit-event () t)
      (:idle ()
	     ;; this lets slime keep working while the main loop is running
             ;; in sbcl using the :fd-handler swank:*communication-style*
             ;; (something similar might help in some other lisps, not sure which though)
	     #+(and sbcl (not sb-thread)) (restartable
                                           (sb-sys:serve-all-events 0))
             (restartable (draw))))))