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with GL.Simple_text, GL.Math, GLU;

package body GLOBE_3D.Portals is

  -- Cheap but fast portal method with rectangles.

  procedure Intersect (A,B: Rectangle; C: out Rectangle; non_empty: out Boolean) is
  begin
    C.X1:= Integer'Max(A.X1,B.X1);
    C.X2:= Integer'Min(A.X2,B.X2);
    C.Y1:= Integer'Max(A.Y1,B.Y1);
    C.Y2:= Integer'Min(A.Y2,B.Y2);
    non_empty:= C.X1 <= C.X2 and C.Y1 <= C.Y2;
  end Intersect;

  procedure Projection(
    P      : in  Point_3D;
    x,y    : out Integer;
    success: out Boolean
  )
  is
    model, proj: GLU.doubleMatrix;
    view: GLU.viewPortRec;
    uu,vv,ww: GL.Double;
    use GL;
    z_a: constant:= 0.0001;
    z_z: constant:= 1.0 - z_a;
    -- GLU sometimes gives fuzzy (e.g. -3612 instead of +4243)
    -- x,y coordinates, with z outside ]0;1[; looks like a wrap-around
    -- of large integer values
  begin
    GLU.Get( GL.MODELVIEW_MATRIX, model );
    GLU.Get( GL.PROJECTION_MATRIX, proj );
    GLU.Get( view );
    GLU.Project( P(0),P(1),P(2), model, proj, view, uu, vv, ww, success );
    success:=
        success
      and then
        ww > z_a
      and then
        ww < z_z
    ;
    if success then
      x:= Integer(uu);
      y:= Integer(vv);
      -- info_a_pnt(0):= (uu,vv,ww);
    else
      x:= -1;
      y:= -1;
    end if;
  end Projection;

  procedure Find_bounding_box(
    o      :     Object_3D'Class;
    face   :     Positive;
    b      : out Rectangle;
    success: out Boolean
  )
  is
    x,y: Integer;
    proj_success: Boolean;
    use GL.Math;
  begin
    b:= ( X1|Y1=> Integer'Last, X2|Y2=> Integer'First );

    for sf in reverse 1 .. o.face_internal(face).last_edge loop
      Projection(
        o.point(o.face_internal(face).P_compact(sf))+o.centre,
        x, y,
        proj_success
      );
      if proj_success then
        -- info_a_pnt(sf):= info_a_pnt(0);
        b.X1:= Integer'Min(b.X1, x);
        b.X2:= Integer'Max(b.X2, x);
        b.Y1:= Integer'Min(b.Y1, y);
        b.Y2:= Integer'Max(b.Y2, y);
      else
        success:= False;
        return; -- we cannot project all edges of the polygon, then fail.
      end if;
    end loop;
    success:= True;
  end Find_bounding_box;

  procedure Draw_boundary( main, clip: Rectangle; portal_depth: Natural:= 0 ) is
    use GL, REF;
    z: constant := 0.0;
    procedure Line(x1,y1,x2,y2: Integer) is
    begin
      Vertex(GL.Double(x1),GL.Double(y1), z);
      Vertex(GL.Double(x2),GL.Double(y2), z);
    end Line;
    procedure Frame_Rect(x1,y1,x2,y2: Integer) is
    begin
      Line(x1,y1,x2,y1);
      Line(x2,y1,x2,y2);
      Line(x2,y2,x1,y2);
      Line(x1,y2,x1,y1);
    end Frame_Rect;
    rect: Rectangle;
    val: constant Real:= 0.3 + 0.7 * Exp(-GL.Double(portal_depth));
    text_size: constant:= 12.5;
  begin
    GL.Disable( GL.LIGHTING );
    GL.Disable( GL.TEXTURE_2D );
    -- GL.Disable( GL.DEPTH_TEST ); -- eeerh, @#*$!, doesn't work!
    -- Workaround, we make the rectangle 1 pixel smaller
    rect:= (clip.X1+1,clip.Y1+1,clip.X2-1,clip.Y2-1);
    -- Push current matrix mode and viewport attributes.
    GL.PushAttrib(GL.TRANSFORM_BIT + GL.VIEWPORT_BIT);
    GL.MatrixMode(GL.PROJECTION);
    GL.PushMatrix;
    GL.LoadIdentity;
    GL.Ortho(
      left     => 0.0,
      right    => GL.Double(main.X2-1),
      bottom   => 0.0,
      top      => GL.Double(main.Y2-1),
      near_val => -1.0,
      far_val  => 1.0
    );

    GL.MatrixMode(GL.MODELVIEW);
    GL.PushMatrix;
    GL.LoadIdentity;

    -- Portal label
    GL.Simple_text.Text_output(
      (GL.Double(clip.X1),  GL.Double(clip.Y2) - text_size, 0.0),
      "Portal depth:" & Integer'Image(portal_depth),
      (0.7, 0.7, val, 0.9),
      text_size,
      GL.Simple_text.Sans_Serif
    );
    -- A green rectangle to signal the clipping area
    GL.Color( 0.1, val, 0.1, 1.0);
    GL_Begin(GL.LINES);
    Frame_Rect( rect.X1,  rect.Y1,  rect.X2,  rect.Y2 );
    GL_End;
    -- A red cross across the area
    GL.Color( val, 0.1, 0.1, 1.0);
    GL_Begin(GL.LINES);
    Line( clip.X1,clip.Y1,clip.X2,clip.Y2 );
    Line( clip.X2,clip.Y1,clip.X1,clip.Y2 );
    GL_End;

    GL.PopMatrix;
    GL.MatrixMode(GL.PROJECTION);
    GL.PopMatrix;
    GL.PopAttrib;
    GL.Enable( GL.LIGHTING );
    -- GL.Enable( GL.DEPTH_TEST );

  end Draw_boundary;

end GLOBE_3D.Portals;