;;;; wh-engine/render/render-system.lisp
;;;; render system main code
(defpackage wh-engine/render
  (:nicknames whe/render)
  (:use common-lisp 3d-vectors 3d-matrices wh-engine)
  (:import-from sb-ext
                weak-pointer weak-pointer-p make-weak-pointer weak-pointer-value)
  (:import-from objective-lisp O!)
  (:export
   ;; render/drawable.lisp
   drawable
   ; virtual properties
   culling-box
   ; methods
   draw

   drawable-test

   ;; render/view.lisp
   view
   ; properties
   render-pass render-mask cull-p
   ; virtual properties
   view-matrix world-matrix
   ; methods
   view-point render-view render-drawable

   *view-width* *view-height* *view-ppu* *pixel-scale*

   ;; render/render-target.lisp
   render-target
   ; properties
   width height framebuffer renderbuffer render-texture
   ; methods
   bind-for-rendering
   ))

(in-package wh-engine/render)

(defun opengl-matrix (matrix)
  (declare (type mat3 matrix))
  (with-fast-matref (m matrix 3)
    (make-array '(16) :initial-contents
                `(,(m 0 0) ,(m 0 1) 0.0 ,(m 0 2)
                  ,(m 1 0) ,(m 1 1) 0.0 ,(m 1 2)
                      0.0      0.0  1.0     0.0
                  ,(m 2 0) ,(m 2 1) 0.0 ,(m 2 2))
                )))

(defvar *view-width* 512
  "View-space width in pixels.")
(defvar *view-height* 384
  "View-space height in pixels.")
(defvar *view-ppu* 64
  "Pixels in view-space per unit in world-space.")

(defvar *pixel-scale* 2
  "Scaling factor for rendered pixels.")

(defvar *world-drawables* ()
  "List of all known drawables.")
(defvar *world-views* ()
  "List of all known views.")

(defun sort-world-views ()
  "Re-sort the *world-views* list by render pass."
  (sort *world-views* #'< :key (lambda (v) (o! (deref-pointer v) render-pass))))

(declaim (special *projection*))

(let (render-target win-width win-height)
  (defun render-system-init ()
    (setf win-width (* *view-width* *pixel-scale*)
          win-height (* *view-height* *pixel-scale*)
          render-target (make-instance 'render-target :width *view-width* :height *view-height*))

    (load #p"wh-engine/render/shaders/basic-shaders.lisp")

    ;; change render target mode
    (gl:bind-texture :texture-2d (o! render-target render-texture))
    (gl:tex-parameter :texture-2d :texture-min-filter :nearest)
    (gl:tex-parameter :texture-2d :texture-mag-filter :nearest)
    (gl:bind-texture :texture-2d 0)

    ;; set up gl
    (gl:matrix-mode :projection)
    (gl:ortho 0 *view-width*
              0 *view-height*
              -1024 1024)
    (gl:matrix-mode :modelview)
    (gl:load-identity)
    (gl:clear-color 0.0 0.0 0.0 1.0)
    (gl:clear :color-buffer :depth-buffer :stencil-buffer))

  (defun render-system-update ()
    ;; draw to render texture
    (o! render-target (bind-for-rendering))
    (gl:clear :color-buffer)
    (gl:enable :depth-test)
    (let ((render-pass nil))
      (loop for view-ptr in *world-views*
            for view = (ensure-live (weak-pointer-value view-ptr))
            when (and (o! view active-p) (o! view actor tree-active-p))
              do (progn
                   (unless (eql (o! view render-pass) render-pass)
                     (setf render-pass (o! view render-pass))
                     (gl:clear :depth-buffer))
                   (o! view (render-view *world-drawables*)))))
    (gl:flush)

    ;; now draw to window
    (gl:bind-framebuffer :framebuffer 0)
    (gl:viewport 0 0 win-width win-height)
    (gl:clear :color-buffer)
    (gl:disable :depth-test)
    (gl:enable :texture-2d)
    (gl:bind-texture :texture-2d (o! render-target render-texture))
    (gl:matrix-mode :modelview)
    (gl:load-identity)

    (gl:with-primitives :quads
      (gl:color 1.0 1.0 1.0 1.0)
      (gl:tex-coord 0.0 0.0)
      (gl:vertex 0.0 0.0)
      (gl:tex-coord 1.0 0.0)
      (gl:vertex *view-width* 0.0)
      (gl:tex-coord 1.0 1.0)
      (gl:vertex *view-width* *view-height*)
      (gl:tex-coord 0.0 1.0)
      (gl:vertex 0.0 *view-height*))

    (gl:disable :texture-2d)

    (gl:flush)))

(register-system :wh-engine/render 'render-system-init 'render-system-update nil)

(install-systems :wh-engine/render)