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/*
 * overlap_rows.c - find the overlap of intervals in two different rows
 */

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

/*
 * ALGORITHM:
 * 	
 * 1.  Get the next interval, next_interal, in row_cb1.
 * 2.  Find the set of intervals it overlaps in row_cb2.
 * 3.  Record the (begin, end) indices of the overlapping intervals from
 *     row_cb2 in the appropriate direction subfield of next_interval
 * 4.  Go back to 1.
 *
 * INPUTS:
 *
 * row_hdr1 - the first row header
 * row_hdr2 - the second row header
 * direction  - the direction to update.  0 - north, 1 - south,
 * 2 - up, 3 - down
 * 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:
 *
 * the intervals array in the row header row_hdr1 are
 * adjusted to reflect the overlap of intervals of row_hdr1 and row_hdr2
 *
 * RETURNS:
 *
 * no return
 */
void
EG_overlap_rows(Row_hdr *row_hdr1, Row_hdr *row_hdr2,
	       int direction, int min_overlap)
{
  int i;
  int overlap_begin;
  int overlap_end;
  
  int start_index;

  start_index = 0;
  for (i=0; i<row_hdr1->size; i++)
    {
      EG_find_overlap(i, start_index, row_hdr1, row_hdr2,
		     min_overlap, &overlap_begin, &overlap_end);
      row_hdr1->intervals[i].overlaps[direction][0] = overlap_begin;
      row_hdr1->intervals[i].overlaps[direction][1] = overlap_end;
      start_index = overlap_end;
    }
}