;;;; wheelwork.lisp

(in-package #:wheelwork)

(defvar *application* nil
  "current application")

(defclass/std unit ()
  ((cached-model cached-projected-matrix :a)
   (container :with :a)
   (base-width base-height :r :std 1.0 :doc "Determined by content.")
   (scale-x scale-y :with :std 1.0)
   (rotation x y :with :std 0.0)
   (opacity :std 1.0 :doc "0.0 indicates it will not be rendred.")))

(defgeneric unit-width (unit))
(defgeneric unit-height (unit)) 
(defgeneric (setf unit-width) (newval unit))
(defgeneric (setf unit-height) (newval unit))

(defun scale-by (unit amount)
  (with-slots (scale-x scale-y) unit
    (setf scale-x (* amount scale-x)
          scale-y (* amount scale-y))))

(defun set-width-preserve-aspect (unit new-width)
  (scale-by unit (/ new-width (unit-width unit))))

(defun set-height-preserve-aspect (unit new-height)
  (scale-by unit (/ new-height (unit-height unit) )))

(defmethod unit-width ((unit unit))
  (with-slots (scale-x base-width) unit
    (* scale-x base-width)))

(defmethod unit-height ((unit unit))
  (with-slots (scale-y base-height) unit
    (* scale-y base-height)))

(defmethod (setf unit-width) (newval (unit unit))
  (with-slots (scale-x base-width) unit
    (setf scale-x (coerce (/ newval base-width) 'single-float))))

(defmethod (setf unit-height) (newval (unit unit))
  (with-slots (scale-y base-height) unit
    (setf scale-y (coerce (/ newval base-height) 'single-float))))

(defmethod (setf closer-mop:slot-value-using-class) :after
    (newval class (unit unit) slot)
  (case (closer-mop:slot-definition-name slot)
    ((x y scale-x scale-y rotation)
     (setf (cached-model unit) nil
           (cached-projected-matrix unit) nil))))

(defclass/std container ()
  ((units :with :a))
  (:documentation "Just a list of units. Made into a class so that
  transformation affine transformations methods can be specialzied on
  whole groups of units"))

(defgeneric drop-unit (unit))
(defgeneric add-unit (container unit))

(defmethod drop-unit ((unit unit))
  "Removes a unit from its container. Returns T if the unit actually was removed."
  (when-let (container (unit-container unit))
    (setf
     (container-units container) (delete unit (container-units container))
     (unit-container unit) nil)
    t))

(defmethod add-unit ((container container) (unit unit))
  "Adds a unit to the end of a container (thus affecting render
order). Makes sure to remove the unit from its current container if
necessary."
  (when (unit-container unit)
    (drop-unit unit))
  (push unit  (container-units container))
  (setf (unit-container unit) container)
  unit)


(defclass/std event-handler ()
  ((event-type handler-function :ri))
  (:metaclass closer-mop:funcallable-standard-class))

(defmethod initialize-instance :after ((eh event-handler) &key)
  (with-slots (handler-function) eh
    (closer-mop:set-funcallable-instance-function eh handler-function)))

(defclass/std listener ()
  ((keydown
    keyup
    mousedown
    mouseup
    mousemotion
    mousewheel
    focus
    blur
    perframe
    after-added
    before-added
    before-dropped
    :r :with :type (or null event-handler) :std nil)
   (keydown-table
    keyup-table
    mousedown-table
    mouseup-table
    mousemotion-table
    mousewheel-table
    focus-table
    blur-table
    perframe-table
    after-added-table
    before-added-table
    before-dropped-table
    :static
    :std (make-hash-table :synchronized t)
    :doc "Keyed by DISPLAY-UNIT instance, holds an EVENT-HANDLER if handler is defined for unit."))
  (:documentation "Event handlers per object. The static hash tables
  are keyed by UNIT and hold Event-Handler instances."))

(defclass/std interactive ()
  ((listener :type (or null listener) :std nil :a)
   (focusablep :std t :doc "Whether or not this object can receive application focus."))
  (:documentation "Supplies an object with a listener slot."))

(defmethod drop-unit :before ((unit interactive))
  (when (unit-container unit) 
    (when-let (handlers (get-handlers-for unit 'before-dropped))
      (dolist (handler handlers) 
        (funcall handler unit)))))

(defmethod add-unit :before ((container container) (unit interactive))
  (when-let (handlers (get-handlers-for unit 'before-added))
    (dolist (handler handlers) 
      (funcall handler container unit))))

(defmethod add-unit :after ((container container) (unit interactive))
  (when-let (handlers (get-handlers-for unit 'after-added))
    (dolist (handler handlers) 
      (funcall handler container unit))))

(defun listener-table-for (listener event-type)
  (ecase event-type
    (keydown (keydown-table listener))
    (keyup   (keyup-table listener))
    (mousedown (mousewheel-table listener))
    (mouseup (mouseup-table listener))
    (mousemotion (mousemotion-table listener))
    (mousewheel (mousewheel-table listener))
    (focus (focus-table listener))
    (blur (blur-table listener))
    (perframe (perframe-table listener))
    (after-added (after-added-table listener))
    (before-added (before-added-table listener))
    (after-dropped (after-dropped-table listener))
    (before-dropped (before-dropped-table listener))))

(defun add-handler (interactive handler)
  (when (null (listener interactive))
    (setf (listener interactive) (make-instance 'listener)))
  (pushnew handler (slot-value (listener interactive) (event-type handler)) :test #'eq)
  (setf
   (gethash interactive (listener-table-for (listener interactive) (event-type handler)))
   t))


(defun remove-handler (interactive handler-or-event-type)
  "Handler can be an instance of EVENT-HANDLER or can be a symbol
  whose name is an event type.  If is an event handler, only that
  handler will be removed. If it is an event type, all events of that
  type name are removed from the object."
  (when (listener interactive)
    (let ((event-type (etypecase handler-or-event-type
                        (keyword (intern (symbol-name handler-or-event-type) :wheelwork))
                        (symbol (intern (symbol-name handler-or-event-type) :wheelwork))
                        (event-handler (event-type handler-or-event-type)))))
      (setf (slot-value (listener interactive) event-type)
            (if (symbolp handler-or-event-type)
                ;; remove everything if a symbol
                nil
                ;; delete just the handler
                (delete handler-or-event-type
                        (slot-value (listener interactive) event-type)
                        :test #'eq)))
      ;; remove from from the global table unless any listeners remain on this event
      (unless (slot-value (listener interactive) event-type)
        (remhash interactive (listener-table-for (listener interactive) event-type))))))



(defun should-listen-for-p (event-type &optional (app *application*))
  (plusp (hash-table-count (listener-table-for (listener app) event-type))))


(defclass/std application (container interactive)
  ((title :with :std "Wheelwork App")
   (asset-root :ri :std #P"./" :doc "Directory under which assets are stored.")
   (asset-classifiers
    :std '(("png" png) ("ttf" font))
    :doc "ALIST of (EXT CLASS). EXT is a string, file estension. CLASS is a symbol, class name.")
   (assets :with :a :std (make-hash-table :test 'equal)
           :doc "maps asset names to asset instances.")
   (scale :with :std 1.0)
   (width height :with :std 800)
   (projection :with :a :doc "The projection matrix for the scene. Orthographic by default.")
   (window :with :a)
   (refocus-on-mousedown-p :std t)
   (focus last-motion-target :with :a)
   (fps :with :std 30 :doc "Frames Per Second")
   (frame-wait :r)))

(defun fps (&optional (app *application*))
  (application-fps app))

(defun (setf fps) (new-val &optional (app *application*))
  (setf (application-fps app) new-val))

(defun can-set-projection-p (app)
  (and (slot-boundp app 'width)
       (slot-boundp app 'height)
       (slot-boundp app 'scale)))

(defun set-projection (app)
  (when (can-set-projection-p app)
    (with-slots (projection scale width height) app 
      ;; set projection matrix
      (setf projection (mat:mortho 0.0 (/ width scale) 0 (/ height scale) -1.0 1.0)))))

(defmethod initialize-instance :after ((app application) &key)
  (set-projection app)
  (setf (listener app) (make-instance 'listener)))

(defun fire-blur-event-on (thing)
  (when-let (blur-handlers (and thing (get-handlers-for thing 'blur)))
    (dolist (handler blur-handlers) 
      (funcall handler thing))))

(defun fire-focus-event-on (thing)
  (when-let (focus-handlers (and thing (get-handlers-for thing 'focus)))
    (dolist (handler focus-handlers)
      (funcall handler thing))))

(defmethod (setf closer-mop:slot-value-using-class ) :before
    (new-value class (app application) slot)
  (case (closer-mop:slot-definition-name slot)
    (focus
     (when (slot-boundp app 'focus) 
       (unless (eq new-value (slot-value app 'focus)) 
         (fire-blur-event-on (slot-value app 'focus))
         (fire-focus-event-on new-value))))))

(defmethod (setf closer-mop:slot-value-using-class) :after
    (new-value class (app application) slot)
  (case (closer-mop:slot-definition-name slot)
    ((scale width height)
     (set-projection app))
    (fps
     (setf (slot-value app 'frame-wait) (/ 1.0 new-value)))))


(defgeneric boot (app)
  (:documentation "Specialized for each subclass of
  APPLICATION. Responsble for setting the app up once the system
  resoruces are avaialble.")
  (:method ((app application)) nil))

(defgeneric shutdown (app)
  (:documentation "Specialzied for each subclass of
  APPLICATION. Called just before cleanup.")
  (:method ((app application)) nil))


(defgeneric cleanup (thing)
  (:documentation "Clean up applications, textures, and so on.")
  (:method ((any t)) nil))

(defparameter +listener-table-slot-names+
  '(keydown-table keyup-table mousedown-table  mouseup-table  mousemotion-table
    focus-table blur-table perframe-table after-added-table before-added-table
    before-dropped-table))

(defmethod cleanup ((app application))
  (loop for asset being the hash-value of (application-assets app)
        do (cleanup asset))
  ;; drop all current handlers
  (let ((listener (listener app))) 
    (dolist (table +listener-table-slot-names+)
      (setf (slot-value listener table) (make-hash-table :synchronized t))))
  (call-next-method))

(defmethod cleanup ((container container))
  (dolist (u (container-units container))
    (cleanup u)))

(defun start (app &key (x :centered) (y :centered))
  (sdl2:with-init (:everything)
    (sdl2:gl-set-attr :context-major-version 3)
    (sdl2:gl-set-attr :context-minor-version 3)
    (sdl2:gl-set-attr :context-profile-mask
                      sdl2-ffi:+sdl-gl-context-profile-core+)
    (sdl2:gl-set-attr :doublebuffer 1)

    (sdl2:with-window (window
                       :flags '(:shown :opengl)
                       :title (application-title app)
                       :w (application-width app)
                       :h (application-height app)
                       :x x :y y)
      (setf (application-window app) window)
      (sdl2:with-gl-context (ctx window)
        (sdl2:gl-make-current window ctx)
        (gl:viewport 0 0 (application-width app) (application-height app))
        ;(gl:enable :depth-test)
        (let ((*application* app)) 
          (unwind-protect
               (progn 
                 (boot app)
                 (eventloop app)
                 (shutdown app))
            (cleanup app)))))))

(defun run-perframe (app)
  (let ((table (perframe-table (listener app)))
        (time (get-universal-time)))
    (loop for target being the hash-key of table
          for handlers = (slot-value (listener target) 'perframe)
          ;; only fire perframe when target is in scene
          when (or (eq app target) (unit-container target)) 
            do (loop for handler in handlers do (funcall handler target time)))))

(defgeneric render (thing))
(defmethod render ((app application))
  (run-perframe app)
  (gl:clear-color 0.0 0.0 0.0 1.0)
  ;(gl:clear :depth-buffer-bit :color-buffer-bit)
  (gl:clear :color-buffer-bit)
  (gl:enable :blend)
  (gl:blend-func :src-alpha :one-minus-src-alpha )
  (dolist (thing (container-units app))
    (render thing))
  (sdl2:gl-swap-window (application-window app))
  (sleep (frame-wait app)))

(defgeneric model-matrix (thing)
  (:documentation "Returns the model matrix"))

(defgeneric projected-matrix (thing)
  (:documentation "Returns the raw array of the model matrix after it
  has been prjected by the application's projecion matrix"))

(defmethod model-matrix :around ((u unit))
  (or (cached-model u)
      (setf (cached-model u)
            (call-next-method))))

(defmethod model-matrix ((u unit))
  (let ((m (mat:meye 4)))
    (with-slots (x y base-width scale-x base-height scale-y rotation) u 
      (let ((uw (* base-width scale-x))
            (uh (* base-height scale-y)))
        (mat:nmtranslate m (vec:vec x y 0.0))

        (mat:nmtranslate m (vec:v* 0.5 (vec:vec uw uh 0.0)))
        (mat:nmrotate  m vec:+vz+ rotation)
        (mat:nmtranslate m (vec:v* -0.5 (vec:vec uw uh 0.0)))
        
        (mat:nmscale m (vec:vec uw uh 1.0))))
    m))

(defmethod projected-matrix ((thing unit))
  (or (cached-projected-matrix thing)
      (setf (cached-projected-matrix thing)
            (mat:marr (mat:m* (application-projection *application*)
                              (model-matrix thing))))))

(defgeneric ensure-loaded (asset)
  (:documentation "Ensures that the asset is loaded into memory and ready for use. Returns the asset."))

(defclass/std asset ()
  ((path :with :ri :std (error "An asset requires a path"))
   (loadedp :with :a)))

(defmethod cleanup :around ((asset asset))
  (when (asset-loadedp asset)
    (call-next-method))
  (setf (asset-loadedp asset) nil))

(defmethod ensure-loaded :around ((thing asset))
  (unless (asset-loadedp thing) 
    (call-next-method)
    (setf (asset-loadedp thing) t))
  thing) 

(defclass/std texture ()
  ((width height id mipmap :with :r)
   (internal-format image-format :ri :with :std :rgba)
   (wrap-s wrap-t :ri :with :std :repeat)
   (min-filter mag-filter :ri :with :std :nearest)))

(defmethod cleanup ((texture texture))
  (gl:delete-texture (texture-id texture)))

(defclass/std png (asset texture) ())

(defmethod ensure-loaded ((png png))
  (with-slots
        (width height id wrap-s wrap-t min-filter mag-filter internal-format image-format)
      png
    (pngload:with-png-in-static-vector (data (asset-path png) :flip-y t)
      (setf width (pngload:width data)
            height (pngload:height data)
            id (gl:gen-texture))
      (gl:bind-texture :texture-2d id)
      (gl:tex-parameter :texture-2d :texture-wrap-s wrap-s)
      (gl:tex-parameter :texture-2d :texture-wrap-t wrap-t)
      (gl:tex-parameter :texture-2d :texture-min-filter min-filter)
      (gl:tex-parameter :texture-2d :texture-mag-filter mag-filter)
      (gl:tex-image-2d :texture-2d
                       0
                       internal-format
                       width
                       height
                       0
                       image-format
                       :unsigned-byte
                       (pngload:data data))
      (gl:bind-texture :texture-2d 0)
      (when (texture-mipmap png)
        (gl:generate-mipmap :texture-2d)))))


(defun refocus-on (target &optional (app *application*))
  "Sets focus of application to TARGET. This works whether or not
TARGET is FOCUSABLEP"
  (setf (application-focus app) target))

(defun get-focus (&optional (app *application*))
  (or (application-focus app) app))

(defun get-handlers-for (unit event-type)
  "EVENT-TYPE must be one of the slot value names for WHEELWORK::LISTENER."
  (?> (unit) listener #$(slot-value $listener event-type)))

(defun eventloop-keydown (app sdl-keysym)
  (let ((target (get-focus app))) 
    (when-let (handlers (get-handlers-for target 'keydown)) 
      (dolist (handler handlers) 
        (apply handler
               target
               (sdl2:scancode sdl-keysym)
               (sdl2:mod-keywords (sdl2:mod-value sdl-keysym)))))))

(defun eventloop-keyup (app sdl-keysym)
  (let ((target (get-focus app))) 
    (when-let (handlers (get-handlers-for target 'keyup)) 
      (dolist (handler handlers) 
        (apply handler
               target
               (sdl2:scancode sdl-keysym)
               (sdl2:mod-keywords (sdl2:mod-value sdl-keysym)))))))

(defun get-rect (unit)
  "Returns a list of vectors representing the path of the smallest
rectangle that encloses the unit. The rectangle is scaled and rotated."
  (with-accessors ((x unit-x) (y unit-y) (w unit-width) (h unit-height) (r unit-rotation)) unit
    (let ((m
            (mat:meye 4))
          (tr
            (vec:vec (+ x (* 0.5 w)) (+ y (* 0.5 h)) 0.0)))
      (mat:nmtranslate m tr)
      (mat:nmrotate  m vec:+vz+ r)
      (mat:nmtranslate m (vec:v* -1.0 tr))

      (list (mat:m* m (vec:vec x y 0.0 1.0))
            (mat:m* m (vec:vec x (+ y h) 0.0 1.0))
            (mat:m* m (vec:vec (+ x w) (+ y h) 0.0 1.0))
            (mat:m* m (vec:vec (+ x w) y 0.0 1.0))
            (mat:m* m (vec:vec x y 0.0 1.0))))))

(defun counterclockwisep (a b c)
  (> (* (- (vec:vx b) (vec:vx a))
        (- (vec:vy c) (vec:vy a)))
     (* (- (vec:vy b) (vec:vy a))
        (- (vec:vx c) (vec:vx a)))))


(defun intersectp (a b c d)
  (or (vec:v= a c) (vec:v= a d) (vec:v= b c) (vec:v= b d)
      (and (not (eq (counterclockwisep a c d) (counterclockwisep b c d)))
           (not (eq (counterclockwisep a b c) (counterclockwisep a b d))))))

(defun path-bounds (path)
  "Path is a list of vectors representing 2d points. Returns the
bounds and width and height as a plist of the form 

(:top N :left N :right N :bottom N :width N :height N)

This is the smallest UNROTATED RECTANGLE that contains the points in
the path."
  (loop
    with max-x = nil
    and max-y = nil
    and min-x = nil
    and min-y = nil
    for vec in path
    for x = (vec:vx vec)
    for y = (vec:vy vec)
    when (or (null max-x) (< max-x x))
      do (setf max-x x)
    when (or (null min-x) (< x min-x))
      do (setf min-x x)
    when (or (null max-y) (< max-y y))
      do (setf max-y y)
    when (or (null min-y) (< y min-y))
      do (setf min-y y)
    finally
       (return (list :top max-y :left min-x :right max-x :bottom min-y
                     :width (- max-x min-x)
                     :height (- max-y min-y)))))

(defun contains-point-p (unit px py)
  (let* ((pt
           (vec:vec px py 0.0 1.0))
         (poly
           (get-rect unit))
         (bounds
           (path-bounds poly))
         (corner
           ;; creating a point guaranteed to be outside of poly
           (vec:vec (- (getf bounds :left) (getf bounds :width))
                    (- (getf bounds :bottom) (getf bounds :height))
                    0.0 1.0)))
    (loop for (p1 p2 . more) on poly
          while p2
          when (intersectp p1 p2 pt corner)
            count 1 into intersection-count
          finally
             (progn
               (return (oddp intersection-count))))))

(defun unit-under (app x y)
  (labels
      ((finder (thing)
         (etypecase thing
           (container
            (find-if #'finder (container-units thing) :from-end t))
           (unit
            (when (contains-point-p thing x y)
              (return-from unit-under thing))))))
    (finder app)))

(defun screen-to-world (x y &optional (app *application*))
  (with-slots (height scale) app
    (list (/ x scale) (/ (- height y) scale))))

(defun eventloop-mousebuttondown (app wx wy clicks button)
  "Searches for a handler to handle applies it if found.

Additionally, if the APPLICATION's REFOCUS-ON-MOUSEDOWN-P is T, try to
give focus to whatever was clicked."
  (destructuring-bind (x y) (screen-to-world wx wy)
    (let ((target
            (or (unit-under app x y)    ; if no unit is under the mouse,
                app)))                  ; then target the app itself
      (when (and (refocus-on-mousedown-p app) (focusablep target))
        (refocus-on target))              
      (when-let (handlers (get-handlers-for target 'mousedown))
        (dolist (handler handlers) 
          (funcall handler target x y clicks button wx wy))))))

(defun eventloop-mousebuttonup (app wx wy clicks button)
  (when (should-listen-for-p 'mouseup app)
    (destructuring-bind (x y) (screen-to-world wx wy)
      (when-let* ((target (or (unit-under app x y)
                              app))
                  (handlers (get-handlers-for target 'mouseup)))
        (dolist (handler handlers) 
          (funcall handler target x y clicks button wx wy))))))

(defun eventloop-mousemotion (app wx wy wxrel wyrel state)
  (when (should-listen-for-p 'mousemotion app)
    (destructuring-bind (x y) (screen-to-world wx wy)
      (destructuring-bind (xrel yrel) (screen-to-world wxrel wyrel)
        (when-let* ((target (or (unit-under app x y)
                                app))
                    (handlers (get-handlers-for target 'mousemotion)))
          (dolist (handler handlers) 
            (funcall handler target x y xrel yrel state wx wy wxrel wyrel)))))))

(defun eventloop-mousewheel (app wx wy dir)
  (when (should-listen-for-p 'mousewheel app)
    (when-let* ((focus (get-focus app))
                (handlers (get-handlers-for focus 'mousewheel)))
      (dolist (handler handlers) 
        (funcall handler focus wx wy dir)))))


(defun eventloop (app)
  (sdl2:with-event-loop (:method :poll)
    (:mousebuttondown
     (:x x :y y :clicks clicks :button button)
     (eventloop-mousebuttondown app x y clicks button))
    (:mousemotion
     (:x x :y y :xrel xrel :yrel yrel :state state)
     (eventloop-mousemotion app x y xrel yrel state))
    (:mousebuttonup
     (:x x :y y :clicks clicks :button button)
     (eventloop-mousebuttonup app x y clicks button))
    (:keydown
     (:keysym keysym)
     (eventloop-keydown app keysym))
    (:keyup
     (:keysym keysym)
     (eventloop-keyup app keysym))
    (:mousewheel
     (:x x :y y :direction dir)
     (eventloop-mousewheel app x y dir))
    (:idle () (render app))
    (:quit () t)))

(defclass/std bitmap (unit interactive)
  ((texture :ri :std (error "A bitmap requires a texture."))
   (vao shader :with :r :static)))

(defmethod cleanup ((bitmap bitmap))
  (with-slots (vao shader) bitmap
    (when vao
      (gl:delete-vertex-arrays (list vao)))
    (when shader
      (gl:delete-program shader))
    (setf vao nil
          shader nil)))

(defun shader-by-type (type)
  (case type
    (:vertex :vertex-shader)
    (:geometry :geometry-shader)
    (:fragment :fragment-shader)))

(defun gl-shader (type stage)
  (let ((shader (gl:create-shader type)))
    (gl:shader-source shader (varjo:glsl-code stage))
    (gl:compile-shader shader)
    (unless (gl:get-shader shader :compile-status)
      (error "failed to compile ~a shader:~%~a~%"
             type (gl:get-shader-info-log shader)))
    shader))

(defun create-shader (&rest sources)
  (let* ((stages
          (varjo:rolling-translate
           (mapcar (lambda (source)
                     (destructuring-bind (type inputs uniforms code) source
                       (varjo:make-stage type inputs uniforms '(:330) code)))
                   sources)))
         (shaders
          (loop
             :for stage :in stages
             :for source :in sources
             :collect (gl-shader (shader-by-type (car source))
                                 stage)))
         (program (gl:create-program)))
    (dolist (shader shaders) (gl:attach-shader program shader))
    (gl:link-program program)
    (unless (gl:get-program program :link-status)
      (error "failed to link program: ~%~a~%"
             (gl:get-program-info-log program)))
    (dolist (shader shaders)
      (gl:detach-shader program shader)
      (gl:delete-shader shader))
    program))


(defun gl-array (type &rest contents)
  (let ((array (gl:alloc-gl-array type (length contents))))
    (dotimes (i (length contents) array)
      (setf (gl:glaref array i) (elt contents i)))))

(defmacro with-gl-array ((var type &rest contents) &body body)
  `(let ((,var (gl-array ,type ,@contents))) 
     (unwind-protect (progn ,@body)
       (gl:free-gl-array ,var))))


(define-symbol-macro +float-size+
    (cffi:foreign-type-size :float))

(defmethod initialize-instance :after ((bitmap bitmap) &key)
  (with-slots (vao shader base-width base-height texture) bitmap
    (setf base-height (texture-height texture)
          base-width (texture-width texture))
    (unless shader
      (setf shader
            (create-shader
             '(:vertex
               ((vert :vec2))
               ((transform :mat4))
               ((values
                 (* transform (vari:vec4 vert 0.0 1.0))
                 vert))) ;color
             '(:fragment
               ((tc :vec2))
               ((tex :sampler-2d))
               ((let ((frag  (vari:texture tex tc)))
                  (if (< (aref frag 3) 0.01)
                      (vari:discard)
                      frag))))))
      (gl:program-uniformi
       shader
       (gl:get-uniform-location shader "TEX")
       0))
    (unless vao
      (setf vao (gl:gen-vertex-array))
      (gl:bind-vertex-array vao)
      (let ((vbo (gl:gen-buffer)))
        (with-gl-array (verts :float
                              0.0 1.0 
                              1.0 0.0 
                              0.0 0.0 
                              
                              0.0 1.0 
                              1.0 1.0 
                              1.0 0.0 )
          (gl:bind-buffer :array-buffer vbo)
          (gl:buffer-data :array-buffer :static-draw verts)))
      (gl:enable-vertex-attrib-array 0)
      (gl:vertex-attrib-pointer 0 2 :float 0 (* +float-size+ 2) 0)
      (gl:bind-buffer :array-buffer 0)
      (gl:bind-vertex-array 0))))

(defmethod render ((bitmap bitmap))
  (with-slots (texture vao shader) bitmap
    (gl:active-texture 0)
    (gl:bind-texture :texture-2d (texture-id texture))
    (gl:use-program shader)
    (gl:program-uniform-matrix-4fv
     shader
     (gl:get-uniform-location shader "TRANSFORM")
     (projected-matrix bitmap))
    (gl:bind-vertex-array vao)    
    (gl:draw-arrays :triangles 0 6)
    (gl:bind-vertex-array 0)))


(defun asset-class-for (asset-id &optional (app *application*))
  "Given an asset-id (see GET-ASSET), retrieve the symbol name of a
the class that will be used to instantiate the asset object. That
class should be a subclass of ASSET.  Additional clases can be added
to the application's ASSET-CLASSIFIERS association list."
  (second (assoc (pathname-type asset-id) (asset-classifiers app) :test #'string-equal)))

(defun get-asset (asset-id &key (app *application*) asset-args)
  "ASSET-ID is a pathname namestring relative to the application's
ASSET-ROOT. GET-ASSET retrieves an already-available asset from the
application's ASSETS table, or, if not available, loads the asset from
disk.

ASSET-ARGS is a plist to pass to make-instance for the given resource.
"
  (or (gethash asset-id (application-assets app))
      (setf (gethash asset-id (application-assets app))
            (ensure-loaded
             (apply 'make-instance
                    (asset-class-for asset-id)
                    :path (uiop:merge-pathnames* asset-id (asset-root app))
                    asset-args)))))

(define-symbol-macro +standard-font-chars+
  " 
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz01234567890\".,!?-'"  )

(defclass/std font (asset)
  ((characters :i :std +standard-font-chars+)
   (oversample :i :doc "ovesampling factor to pass to cl-fond:make-font")
   (object :with :r :doc "The font as returned from cl-fond:make-font")))

(defmethod ensure-loaded ((font font))
  (with-slots (path characters oversample object) font
    (setf object (cl-fond:make-font path characters :oversample oversample))))


(defclass/std text (unit interactive)
  ((font :with :ri :std (error "A font is required") :type font)
   (content :with :ri :std "")
   (color :with :std #(1.0 1.0 1.0 1.0))
   (vao elem-count newlines :r)
   (shader :with :static :r)))

(defmethod model-matrix ((text text))
  (let ((m (mat:meye 4)))
    (with-slots (font newlines x y base-width base-height scale-x scale-y rotation) text 
      (let* ((text-height
               (cl-fond:text-height (font-object font)))
             (baseline-offset
              (* newlines text-height))
             (rotation-baseline-offset
               (* 2 newlines text-height )))
        (mat:nmtranslate m (vec:vec x
                                    (+ y
                                       (*
                                        scale-y
                                        baseline-offset))
                                    0.0))

        (mat:nmtranslate m (vec:v* 0.5 (vec:vec (* scale-x base-width)
                                                (* scale-y (- base-height rotation-baseline-offset) )
                                                0.0)))
        (mat:nmrotate  m vec:+vz+ rotation)
        (mat:nmtranslate m (vec:v* -0.5 (vec:vec (* scale-x base-width )
                                                 (* scale-y (- base-height rotation-baseline-offset))
                                                 0.0))))
      
      (mat:nmscale m (vec:vec scale-x scale-y 1.0))
      m)))

(defmethod initialize-instance :after ((text text) &key)
  (with-slots (content newlines font vao elem-count shader base-width base-height scale-x scale-y) text
    (unless shader
      (setf shader
            (create-shader
             '(:vertex
               ((vert :vec2) (col :vec2))
               ((transform :mat4))
               ((values
                 (* transform (vari:vec4 vert 0.0 1.0))
                 col)))
             '(:fragment
               ((tc :vec2))
               ((tex :sampler-2d)
                (color :vec4))
               ((* color (aref (vari:texture tex tc) 0)))))))
    (multiple-value-bind (vao% count%) (cl-fond:compute-text (font-object font) content)
      (setf vao vao%
            elem-count count%))
    (setf newlines (count #\newline content))
    (hq:with-plist (l r) (cl-fond:compute-extent (font-object font) content)
      (setf base-width (- r l)
            base-height (* (cl-fond:text-height (font-object font))
                           (1+ newlines))))))

(defmethod cleanup ((text text))
  (with-slots (vao shader) text
    (gl:delete-vertex-arrays (list vao))
    (when shader
      (gl:delete-program shader))
    (setf vao nil
          shader nil)))

(defmethod render ((text text))
  (with-slots (shader font vao elem-count color) text
    (gl:use-program shader)
    (gl:active-texture 0)
    (gl:bind-texture :texture-2d (cl-fond:texture (font-object font)))
    (gl:program-uniform-matrix-4fv
     shader
     (gl:get-uniform-location shader "TRANSFORM")
     (projected-matrix text))
    (gl:program-uniformi
     shader
     (gl:get-uniform-location shader "TEX")
     0)
    (gl:program-uniformfv
     shader
     (gl:get-uniform-location shader "COLOR")
     color)
    (gl:bind-vertex-array vao)
    (%gl:draw-elements :triangles elem-count :unsigned-int 0)
    (gl:bind-vertex-array 0)))




(defmacro defhandler (name handler)
  "Defines a handler - binds (FDEFINITION NAME) to HANDLER, which
should be an expression that evaluates to an instance of
EVENT-HANDLER, which is funcallable.  It is define such that handlers
can be redefined using this form to support interactive development."
  (let ((handler-var (gensym)))
    `(let ((,handler-var ,handler))
       (if-let (extant (and (fboundp ',name)
                            (fdefinition ',name)))
         (closer-mop:set-funcallable-instance-function extant (handler-function ,handler-var))
         (setf (fdefinition ',name) ,handler-var)))))


(defmacro on-perframe
    ((&optional (target 'target) (time 'time)) &body body)
  "Creates a handler for 'PERFRAME events"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::perframe
    :handler-function (lambda (,(intern (symbol-name target))
                               ,(intern (symbol-name time)))
                        (declare (ignorable ,(intern (symbol-name target))
                                            ,(time (intern (symbol-name time)))))
                        ,@body)))

(defmacro on-keydown
    ((&optional (target 'target) (scancode 'scancode) (modifiers 'modifiers)) &body body)
  "Creates a lambda suitable for the value of a keydown event
  handler. The function accepts two positional arguments TARGET and
  SCANCODE and one &REST argument MODIFIERS.

  SCANCODE will be a keyword of the form :SCANCODE-A, :SCANCODE-B ...

  The members of MODIFIERS look like :LSHIFT, :RCTRL, RALT, etc"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::keydown
    :handler-function (lambda (,(intern (symbol-name target))
                               ,(intern (symbol-name scancode))
                               &rest ,(intern (symbol-name modifiers)))
                        (declare (ignorable ,(intern (symbol-name target))
                                            ,(intern (symbol-name scancode))
                                            ,(intern (symbol-name modifiers))))
                        ,@body)))

(defmacro on-keyup
    ((&optional (target 'target) (scancode 'scancode) (modifiers 'modifiers)) &body body)
  "Creates a lambda suitable for the value of a keyup event
  handler. The function accepts two positional arguments TARGET and
  SCANCODE and one &REST argument MODIFIERS.

  SCANCODE will be a keyword of the form :SCANCODE-A, :SCANCODE-B ...

  The members of MODIFIERS look like :LSHIFT, :RCTRL, RALT, etc"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::keyup
    :handler-function (lambda (,(intern (symbol-name target))
                               ,(intern (symbol-name scancode))
                               &rest ,(intern (symbol-name modifiers)))
                        (declare (ignorable ,(intern (symbol-name target))
                                            ,(intern (symbol-name scancode))
                                            ,(intern (symbol-name modifiers))))
                        ,@body)))

(defmacro on-mousemotion
    ((&optional
        (target 'target)
        (x 'x) (y 'y)
        (xrel 'xrel) (yrel 'yrel)
        (state 'state)
        (win-x 'win-x) (win-y 'win-y)
        (win-xrel 'win-xrel) (win-yrel 'win-yrel))
     &body body)
  "Creates a handler for MOUSEMOTION events"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::mousemotion
    :handler-function (lambda (,(intern (symbol-name target))
                               ,(intern (symbol-name x))
                               ,(intern (symbol-name y))
                               ,(intern (symbol-name xrel))
                               ,(intern (symbol-name yrel))
                               ,(intern (symbol-name state))
                               ,(intern (symbol-name win-x))
                               ,(intern (symbol-name win-y))
                               ,(intern (symbol-name win-xrel))
                               ,(intern (symbol-name win-yrel)))
                        (declare (ignorable ,(intern (symbol-name target))
                                            ,(intern (symbol-name x))
                                            ,(intern (symbol-name y))
                                            ,(intern (symbol-name xrel))
                                            ,(intern (symbol-name yrel))
                                            ,(intern (symbol-name state))
                                            ,(intern (symbol-name win-x))
                                            ,(intern (symbol-name win-y))
                                            ,(intern (symbol-name win-xrel))
                                            ,(intern (symbol-name win-yrel))))
                        ,@body)))

(defmacro on-mousedown
    ((&optional (target 'target)
        (x 'x) (y 'y)
        (clicks 'clicks) (button 'button)
        (win-x 'win-x) (win-y 'win-y))
     &body body)
  "Creates a handler for MOUSEDOWN events"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::mousedown
    :handler-function (lambda
                          (,(intern (symbol-name target))
                               ,(intern (symbol-name x))
                               ,(intern (symbol-name y))
                               ,(intern (symbol-name clicks))
                               ,(intern (symbol-name button))
                               ,(intern (symbol-name win-x))
                               ,(intern (symbol-name win-y)))
                        (declare
                         (ignorable ,(intern (symbol-name target))
                                            ,(intern (symbol-name x))
                                            ,(intern (symbol-name y))
                                            ,(intern (symbol-name clicks))
                                            ,(intern (symbol-name button))
                                            ,(intern (symbol-name win-x))
                                            ,(intern (symbol-name win-y))))
                        ,@body)))

(defmacro on-mouseup
    ((&optional (target 'target)
        (x 'x) (y 'y)
        (clicks 'clicks) (button 'button)
        (win-x 'win-x) (win-y 'win-y))
     &body body)
  "Creates a handler for MOUSEUP events"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::mouseup
    :handler-function (lambda
                          (,(intern (symbol-name target))
                               ,(intern (symbol-name x))
                               ,(intern (symbol-name y))
                               ,(intern (symbol-name clicks))
                               ,(intern (symbol-name button))
                               ,(intern (symbol-name win-x))
                               ,(intern (symbol-name win-y)))
                        (declare
                         (ignorable ,(intern (symbol-name target))
                                            ,(intern (symbol-name x))
                                            ,(intern (symbol-name y))
                                            ,(intern (symbol-name clicks))
                                            ,(intern (symbol-name button))
                                            ,(intern (symbol-name win-x))
                                            ,(intern (symbol-name win-y))))
                        ,@body)))

(defmacro on-mousewheel
    ((&optional (target 'target) (horiz 'horiz) (vert 'vert) (dir 'dir)) &body body)
  "Creates a handler for MOUSEWHEEL events"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::mousewheel
    :handler-function (lambda
                          (,(intern (symbol-name target))
                               ,(intern (symbol-name horiz))
                               ,(intern (symbol-name vert))
                               ,(intern (symbol-name dir)))
                        (declare
                         (ignorable ,(intern (symbol-name target))
                                            ,(intern (symbol-name horiz))
                                            ,(intern (symbol-name vert))
                                            ,(intern (symbol-name dir))))
                        ,@body)))

(defmacro on-blur
    ((&optional (target 'target)) &body body)
  "Creates a handler for BLUR events. BLUR is a psuedo event that
fires whenever an object loses focus."
  `(make-instance
    'event-handler
    :event-type 'wheelwork::blur
    :handler-function (lambda
                          (,(intern (symbol-name target)))
                        (declare
                         (ignorable ,(intern (symbol-name target))))
                        ,@body)))

(defmacro on-focus
    ((&optional (target 'target)) &body body)
  "Creates a handler for a FOCUS event. FOCUS is a pusedo event that
fires when the FOCUS slot of the current APPLICATION instance is changed.
"
  `(make-instance
    'event-handler
    :event-type 'wheelwork::focus
    :handler-function (lambda
                          (,(intern (symbol-name target)))
                        (declare
                         (ignorable ,(intern (symbol-name target))))
                        ,@body)))

(defmacro on-before-dropped
    ((&optional (target 'target)) &body body)
  "Creates a handler for BEFORE-DROPPED events, which fire before a
  unit is removed from its container."
  `(make-instance
    'event-handler
    :event-type 'wheelwork::before-dropped
    :handler-function (lambda
                          (,(intern (symbol-name target)))
                        (declare
                         (ignorable ,(intern (symbol-name target))))
                        ,@body)))

(defmacro on-before-added
    ((&optional (container 'container) (target 'target)) &body body)
  "Creates a handler for BEFORE-ADDED events, which fire before a unit
  is added to a container."
  `(make-instance
    'event-handler
    :event-type 'wheelwork::before-added
    :handler-function (lambda
                          (,(intern (symbol-name container))
                           ,(intern (symbol-name target)))
                        (declare
                         (ignorable
                          ,(intern (symbol-name container))
                          ,(intern (symbol-name target))))
                        ,@body)))


(defmacro on-after-added
    ((&optional (container 'container) (target 'target)) &body body)
  "Creates a handler for AFTER-ADDED events, which fire after a unit
  is added to a container."
  `(make-instance
    'event-handler
    :event-type 'wheelwork::after-added
    :handler-function (lambda
                          (,(intern (symbol-name container))
                           ,(intern (symbol-name target)))
                        (declare
                         (ignorable
                          ,(intern (symbol-name container))
                          ,(intern (symbol-name target))))
                        ,@body)))

;;; Utility

(define-symbol-macro +pi-over-180+ 0.017453292519943295d0)

(defun radians (degrees)
  "Converse DEGREES to radians"
  (* degrees +pi-over-180+))