with
     openGL.Impostor,
     openGL.Visual,
     openGL.Renderer.lean;

limited
with
     openGL.Camera;

private
with
     ada.Containers.hashed_Maps,
     ada.unchecked_Conversion;

package openGL.Impostorer
--
-- Provides an impostoring system.
--
is
   type Item is tagged limited private;
   type View is access all Item'Class;


   ---------
   --- Forge
   --

   procedure define   (Self : in out Item);
   procedure destruct (Self : in out Item);


   --------------
   --- Attributes
   --

   function  impostor_Count       (Self : in     Item) return Natural;


   function  impostor_size_Min    (Self : in     Item'Class)     return Real;
   procedure impostor_size_Min_is (Self : in out Item'Class;   Now : in Real);
   --
   -- Visuals whose projected size falls below this minimum will be substituted with impostors.


   procedure Camera_is   (Self : in out Item'Class;   Now : access Camera.item'Class);
   function  Camera      (Self : in     Item'Class)  return access Camera.item'Class;

   procedure Renderer_is (Self : in out Item'Class;   Now : in Renderer.lean.view);
   function  Renderer    (Self : in     Item'Class)     return Renderer.lean.view;


   --------------
   --  Operations
   --

   procedure substitute (Self : in out Item;   the_Visuals : in out Visual.views;
                                               Camera      : access openGL.Camera.item'Class);


private

   -- visual_Maps_of_impostor
   --

   use type Visual  .view,
            Impostor.view;

   function Hash is new ada.unchecked_Conversion (Visual.view, ada.Containers.Hash_type);

   package visual_Maps_of_impostor is new ada.Containers.hashed_Maps (Visual  .view,
                                                                      Impostor.view,
                                                                      Hash            => Hash,
                                                                      equivalent_Keys => "=");
   subtype visual_Map_of_impostor is visual_Maps_of_impostor.Map;


   -- impostor_load_Balancer
   --

   package impostor_load_Balancer
   is
      type Slot is
         record
            max_Faces   : Positive;
            max_Updates : Positive;

            Impostors       : Impostor.views (1 .. 20_000);
            impostors_Count : Natural := 0;
         end record;

      type Slots      is array (Positive range <>) of Slot;
      type Slots_view is access all Slots;

   end impostor_load_Balancer;


   default_Slots : aliased impostor_load_Balancer.Slots := (1 => (max_Faces =>  100,          max_Updates =>  20, others => <>),
                                                            2 => (max_Faces => 1000,          max_Updates =>  15, others => <>),
                                                            3 => (max_Faces => Positive'Last, max_Updates =>  12, others => <>));
   -- Impostorer
   --
   type   Camera_view is access all openGL.Camera       .item'Class;
   type Renderer_view is access all openGL.Renderer.lean.item'Class;

   type Item is tagged limited
      record
         impostor_size_Min : safe_Real;

         visual_Map_of_imposter : visual_Maps_of_impostor.Map;
         impostor_load_Slots    : impostor_load_Balancer.Slots_view := new impostor_load_Balancer.Slots' (default_Slots);

         Camera   :   Camera_view;
         Renderer : Renderer_view;
      end record;


end openGL.Impostorer;