#include "unigi.ext/main.h"

void unigi_ext_texture_draw(
	unigi_ext_type_texture tex,
	unigi_ext_type_texture buffer,
	unigi_ext_type_rect texbounds,
	unigi_ext_type_rect bufbounds
) {
   unigi_ext_type_2d_coord texwidth;
   unigi_ext_type_2d_coord texheight;
   unigi_ext_type_2d_coord outwidth;
   unigi_ext_type_2d_coord outheight;
   unigi_ext_type_2d_coord x;
   unigi_ext_type_2d_coord y;
   unigi_type_resolution_1d_coord texi;
   unigi_type_resolution_1d_coord bufi;
   unigi_ext_type_2d_coord stepx;
   unigi_ext_type_2d_coord stepy;
   unigi_ext_type_2d_coord texx;
   unigi_ext_type_2d_coord texy;
   
   unigi_ext_rect_dimensions(texbounds, &texwidth, &texheight);
   unigi_ext_rect_dimensions(bufbounds, &outwidth, &outheight);
   // We precalculate the step through the texture to avoid division and
   // multiplication per pixel. We also expand the range so we can use
   // integers. By using 256, we are essentially adding 8 bits of "decimal
   // point". If you need more bits (or less), just change this to some other
   // power of 2. 
   stepx = (1 << unigi_ext_texture_fixedpointdepth) * (float)texwidth / outwidth;
   stepy = (1 << unigi_ext_texture_fixedpointdepth) * (float)texheight / outheight;
   texx = (1 << unigi_ext_texture_fixedpointdepth) * texbounds.x1;
   texy = (1 << unigi_ext_texture_fixedpointdepth) * texbounds.y1;
   //log("%f,%f step %f,%f", texx, texy, stepx, stepy);
   // Buffer is R G B for each pixel, then across then down. If you want X, Y,
   // it's: 3 * (x + y * width)
   for(y = bufbounds.y1; y < bufbounds.y2; y++) {
      texx = texbounds.x1;
      for(x = bufbounds.x1; x < bufbounds.x2; x++) {
         // And then with the shift, it is log2(256), or whatever you shifted
         // by up there. So 512 would be 9, because 2^9 = 512
         texi = (texx >> unigi_ext_texture_fixedpointdepth) + tex.width * (texy >> unigi_ext_texture_fixedpointdepth); // 'texy >> FIXEDPOINTDEPTH' could be calculated per y-iteration
         bufi = x + y * buffer.width; // 'y * buffer.width' could be calculated per y-iteration
         buffer.pixels[bufi] = tex.pixels[texi];
         texx += stepx;
         bufi += 1;
      }
      texy += stepy;
   }
}

void unigi_ext_rect_dimensions(
	unigi_ext_type_rect bounds,
	unigi_ext_type_2d_coord * width,
	unigi_ext_type_2d_coord * height
) {
	*width = abs(bounds.x2 - bounds.x1);
	*height = abs(bounds.y2 - bounds.y1);
}