#include "lephisto.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 glTexture* at, const int asx, const int asy,
                  const Vec2* ap, const glTexture* bt,
                  const int bsx, const int bsy, const Vec2* bp) {

  int x,y;
  int ax1, ax2, ay1, ay2;
  int bx1, bx2, by1, by2;
  int inter_x0, inter_x1, inter_y0, inter_y1;
  int rasy, rbsy;
  int abx, aby, bbx, bby;

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

  // b - cube coords.
  bx1 = (int)VX(*bp) - (int)(bt->sw)/2;
  by1 = (int)VY(*bp) - (int)(bt->sh)/2;
  bx2 = bx1 + (int)(bt->sw) - 1;
  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.
  inter_x0 = MAX(ax1, bx1);
  inter_x1 = MIN(ax2, bx2);
  inter_y0 = MAX(ay1, by1);
  inter_y1 = MIN(ay2, by2);

  // Real vertical sprite value (flipped).
  rasy = at->sy - asy - 1;
  rbsy = bt->sy - bsy - 1;

  // Set up the base points.
  abx = asx*(int)(at->sw)   - ax1;
  aby = rasy*(int)(at->sh)  - ay1;
  bbx = bsx*(int)(bt->sw)   - bx1;
  bby = rbsy*(int)(bt->sh)  - by1;

  for(y = inter_y0; y <= inter_y1; y++)
    for(x = inter_x0; x <= inter_x1; x++)
      // Compute offsets for surface before passing to TransparentPixel test.
      if((!gl_isTrans(at, abx + x, aby + y)) &&
         (!gl_isTrans(bt, bbx + x, bby + y)))
        return 1;

  return 0;
}