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/*
 * find_overlap.c - find all intervals in a control block that overlap a
 * given interval
 */

#include <sys/types.h>
#include <euclid/clump.h>

/*
 * Inputs:
 * x - the xth interval from the intervals in row_hdr1
 * start   - the interval in row_cb2 to start looking for overlap
 * row_hdr1 - row header containing x
 * row_hdr2 - the other row header
 * min_overlap - 
 *   If min_overlap is +n, then the intervals must overlap by n
 *   grid positions.
 *   If min_overlap is 0, the intervals 'overlap' if their corners 
 *   touch diagonally.
 *   If min_overlap is -n, the intervals are considered to
 *   overlap if there is a gap of n grid positions or less between them.
 *
 * Outputs:
 * overlap_begin - the first interval in row_hdr2 that overlaps x
 * overlap_end	- the last interval in row_hdr2 that overlaps x
 *
 * NOTE: The variable overlap_begin is initialized to be greater than
 * overlap_end.  It will be reset if there is an interval in row_hdr2 that
 * overlaps x.
 *
 * Returns:
 * 1 if x overlaps an interval in row_hdr2
 * 0 otherwise
 */

int
EG_find_overlap(int x, int start, Row_hdr *row_hdr1, Row_hdr *row_hdr2, int min_overlap, int *overlap_begin, int *overlap_end)

{
  int j;

  /*
   * Initialize overlap_begin to an impossible value and set overlap_end
   * to the last possible value.
   */
  *overlap_begin = row_hdr2->size+1;
  *overlap_end = row_hdr2->size;

  /* find overlap_begin */
  for (j=start; j<row_hdr2->size; j++)
    {
      switch (EG_overlap(&(row_hdr1->intervals[x]), &(row_hdr2->intervals[j]),
			min_overlap))
	{
	case -1:
	  /* interval x is before interval j */
	  *overlap_end = j;
	  return(0);

	case 0:
	  /* interval x and interval j overlap */
	  *overlap_begin = j;
	  j++;
	  while ((j < row_hdr2->size) &&
		 EG_overlap(&(row_hdr1->intervals[x]),
			 &(row_hdr2->intervals[j]),
			 min_overlap) == 0) {
	    j++;
	  }
	  *overlap_end = j-1;
	  return(1);

	case 1:
	  /* interval x is after interval x */
	  continue;
	}
    }
  return(0);
}