(local pxl8 (require :pxl8))

(var angle-x 0)
(var angle-y 0)
(var angle-z 0)
(var auto-rotate true)
(var orthographic true)
(var wireframe true)
(var time 0)
(var zoom 5.0)

(fn make-cube-vertices []
  [[-1 -1 -1] [1 -1 -1] [1 1 -1] [-1 1 -1]
   [-1 -1 1] [1 -1 1] [1 1 1] [-1 1 1]])

(fn make-cube-faces []
  [[0 1 2] [0 2 3]
   [1 5 6] [1 6 2]
   [5 4 7] [5 7 6]
   [4 0 3] [4 3 7]
   [3 2 6] [3 6 7]
   [4 5 1] [4 1 0]])

(fn get-face-color [face-idx]
  (let [colors [12 22 30 16 28 20]]
    (. colors (+ 1 (% face-idx 6)))))

(fn cube-update [dt]
  (set time (+ time dt))

  (when (pxl8.key_down "w")
    (set angle-x (- angle-x (* dt 2.0))))
  (when (pxl8.key_down "s")
    (set angle-x (+ angle-x (* dt 2.0))))
  (when (pxl8.key_down "a")
    (set angle-y (- angle-y (* dt 2.0))))
  (when (pxl8.key_down "d")
    (set angle-y (+ angle-y (* dt 2.0))))
  (when (pxl8.key_down "q")
    (set angle-z (- angle-z (* dt 2.0))))
  (when (pxl8.key_down "e")
    (set angle-z (+ angle-z (* dt 2.0))))

  (when (pxl8.key_pressed " ")
    (set wireframe (not wireframe)))
  (when (pxl8.key_pressed "r")
    (set auto-rotate (not auto-rotate)))
  (when (pxl8.key_pressed "p")
    (set orthographic (not orthographic)))

  (when (pxl8.key_down "=")
    (set zoom (- zoom (* dt 2.0))))
  (when (pxl8.key_down "-")
    (set zoom (+ zoom (* dt 2.0))))
  (set zoom (math.max 1.0 (math.min zoom 20.0)))

  (when auto-rotate
    (set angle-x (+ angle-x (* dt 0.7)))
    (set angle-y (+ angle-y (* dt 0.5)))
    (set angle-z (+ angle-z (* dt 0.3)))))

(fn cube-frame []
  (pxl8.clr 0)

  (pxl8.clear_zbuffer)
  (pxl8.set_wireframe wireframe)
  (pxl8.set_backface_culling true)

  (if orthographic
      (let [size (* 2.5 (/ zoom 5.0))
            aspect (/ (pxl8.get_width) (pxl8.get_height))
            w (* size aspect)
            h size]
        (pxl8.set_projection (pxl8.mat4_ortho (- w) w (- h) h 1.0 50.0)))
      (let [aspect (/ (pxl8.get_width) (pxl8.get_height))
            fov (/ 3.14159 (+ 2.0 (/ zoom 5.0)))]
        (pxl8.set_projection (pxl8.mat4_perspective fov aspect 1.0 50.0))))

  (pxl8.set_view (pxl8.mat4_lookat [0 0 zoom] [0 0 0] [0 1 0]))

  (let [model (-> (pxl8.mat4_identity)
                  (pxl8.mat4_multiply (pxl8.mat4_rotate_x angle-x))
                  (pxl8.mat4_multiply (pxl8.mat4_rotate_y angle-y))
                  (pxl8.mat4_multiply (pxl8.mat4_rotate_z angle-z)))]
    (pxl8.set_model model))

  (let [vertices (make-cube-vertices)
        faces (make-cube-faces)]
    (each [i face (ipairs faces)]
      (let [[i0 i1 i2] face
            v0 (. vertices (+ 1 i0))
            v1 (. vertices (+ 1 i1))
            v2 (. vertices (+ 1 i2))
            color (get-face-color (math.floor (/ (- i 1) 2)))]
        (pxl8.draw_triangle_3d v0 v1 v2 color)))))

{:update cube-update
 :frame cube-frame}