/* function d = find_min_dist(line_x,line_y,x,y)

   Given a grid (x,y) and a line (line_x,line_y) compute the
   minimum distance from each point of (x,y) to a point on
   the line.

   Written by George Beckett - Matlab 5.3 MEX,
   Friday 7th April 2000.
*/

/* All MEX prototypes are stored in the mex.h header file which must
   be included.
*/

#include <math.h>
#include "mex.h"

#define DEBUG 0
#define LARGEST_DOMAIN 100

void mexFunction(int nlhs, mxArray *plhs[],
		 int nrhs, const mxArray *prhs[]){
  unsigned int i,j, k;
  unsigned long int loc = 0; /* counter */
  unsigned int m, n, n2; /* dimension stores */
  double *plx = NULL, *ply = NULL; /* pointers to matrices */
  double *px = NULL, *py = NULL, *pd = NULL;
  double dist, min_dist; /* temporary stores */

  /* Firstly, validate input and output arguments. */
  if(nrhs != 4)
    mexErrMsgTxt("Invalid no. input arguments.");
  else if(nlhs != 1)
    mexErrMsgTxt("Invalid no. output arguments.");

  /* Then read input arguments. */
  plx = (double *)mxGetPr(prhs[0]);
  ply = (double *)mxGetPr(prhs[1]);
  px = (double *)mxGetPr(prhs[2]);
  py = (double *)mxGetPr(prhs[3]);

  /* Get size of grid matrices and length of line vector. */
  m = mxGetM(prhs[2]);
  n = mxGetN(prhs[2]);
  n2 = mxGetN(prhs[0]);

  /* Allocate space for the minimum distance matrix. */
  plhs[0] = mxCreateDoubleMatrix(m, n, mxREAL);
  if(plhs[0] == NULL)
    mexErrMsgTxt("Could not create matrix min_dist. Memory?");
  pd = (double *)mxGetPr(plhs[0]);

  /* Step through the mesh one point at a time. */
  for(j = 0; j < n; j++){
    for(i = 0; i < m; i++){
      min_dist = LARGEST_DOMAIN;
      
      /* Step along the line a point at a time. */
      for(k = 0; k < n2; k++){
	dist = (plx[k]-px[loc])*(plx[k]-px[loc]) + \
	  (ply[k]-py[loc])*(ply[k]-py[loc]);
      
	if(dist < min_dist)
	  min_dist = dist;
      }

      pd[loc++] = min_dist;
    }
  }

  /* No housekeeping to be done here. */
  return;
}