#include<general.h>
#include<cross-section.h>
#include<coord.h>

/** @brief Calculates cross-section of vesicle with plane.
 *
 * Function returns points of cross-section of vesicle with plane. Plane is described with equation $ax+by+cz+d=0$. Algorithm extracts coordinates of each vertex of a vesicle and then:
 *
 * if a distance of point to plane (given by equation $D=\frac{ax_0+by_0+cz_0+d}{\sqrt{a^2+b^2+c^2}}$, where $x_0$, $y_0$ and $z_0$ are coordinates of a given vertex) is less than maximal allowed distance between vertices {\tt sqrt(vesicle->dmax)} than vertex is a candidate for crossection calculation.
 *
 */
ts_coord_list *get_crossection_with_plane(ts_vesicle *vesicle,ts_double a,ts_double b,ts_double c, ts_double d){


	ts_uint i, j;
	ts_double pp,Dsq; // distance from the plane squared
	ts_double ppn; // distance from the plane squared of a neighbor
	ts_double u; //factor to scale vector from first vector to the second to get intersection
	ts_vertex *vtx;

	ts_coord_list *pts=init_coord_list();
	for(i=0;i<vesicle->vlist->n;i++){
		vtx=vesicle->vlist->vtx[i];

		pp=vtx->x*a+vtx->y*b+vtx->z*c+d;
		Dsq=pp*pp/(a*a+b*b+c*c);
		if(Dsq<vesicle->dmax){
			for(j=0;j<vtx->neigh_no;j++){
				ppn=vtx->neigh[j]->x*a+vtx->neigh[j]->y*b+vtx->neigh[j]->z*c+d;
				if(pp*ppn<0){ //the combination of vertices are good candidates for a crossection
					u=pp/(a*(vtx->x-vtx->neigh[j]->x)+b*(vtx->y-vtx->neigh[j]->y)+c*(vtx->z-vtx->neigh[j]->z));
					add_coord(pts, vtx->x+u*(vtx->neigh[j]->x - vtx->x),
							vtx->y+u*(vtx->neigh[j]->y - vtx->y),		
							vtx->z+u*(vtx->neigh[j]->z - vtx->z),
							TS_COORD_CARTESIAN);		
				}
			}
		}
	}
	return pts;
}