#include "main.h"
#include "log.h"
#include "collision.h"

// Collide sprite at (asx, asy) int 'at' at pos 'ap' with sprite at (bsx,bsy) in 'bt' at 'bp'
// at   - Texture a.
// asx  - Position of x of sprite a.
// asy  - Position of y of sprite a.
// ap   - Position in space of sprite a.
// bt   - Texture b.
// bsx  - Position of x of sprite b.
// bsy  - Position of y of sprite b.
// bp   - Position in space of sprite b.
int CollideSprite(const gl_texture* at, const int asx, const int asy, const Vec2* ap,
      const gl_texture* bt, const int bsx, const int bsy, const Vec2* bp) {
  
  int x,y;

  // a - cube coords.
  int ax1 = (int)VX(*ap) - (int)(at->sw)/2;
  int ay1 = (int)VY(*ap) - (int)(at->sh)/2;
  int ax2 = ax1 + (int)(at->sw) - 1;
  int ay2 = ay1 + (int)(at->sh) - 1;

  // b - cube coords.
  int bx1 = (int)VX(*bp) - (int)(bt->sw)/2;
  int by1 = (int)VY(*bp) - (int)(bt->sh)/2;
  int bx2 = bx1 + (int)(bt->sw) - 1;
  int by2 = by1 + (int)(bt->sh) - 1;
  
  // Check if bounding boxes intersect.
  if((bx2 < ax1) || (ax2 < bx1)) return 0;
  if((by2 < ay1) || (ay2 < by1)) return 0;

  // Define the remaining binding box.
  int inter_x0 = MAX(ax1, bx1);
  int inter_x1 = MIN(ax2, bx2);
  int inter_y0 = MAX(ay1, by1);
  int inter_y1 = MIN(ay2, by2);

  for(y = inter_y0; y <= inter_y1; y++)
    for(x = inter_x0; x <= inter_x1; x++)
      // Computer offsets for surface before passing to TransparentPixel test.
      if((!gl_isTrans(at, asx*(int)(at->sw) + x-ax1, asy*(int)(at->sh) + y-ay1)) &&
            (!gl_isTrans(bt, bsx*(int)(bt->sw) + x-bx1, bsy*(int)(bt->sh) + y-by1)))
        return 1;

  return 0;
}