/*
------------------------------------------------------------------------------
  By Bob Jenkins, 1989, in relation to my Master's Thesis.  Public Domain.
  This module handles entire knots.
------------------------------------------------------------------------------
*/
#ifndef STANDARD
#include "standard.h"
#endif
#ifndef DLLINK
#include "dllink.h"
#endif
#ifndef KNOT
#include "knot.h"
#endif

/*
------------------------------------------------------------------------------
  Assumes the dllinks all form cycles
  This displays each string once by listing its crossings in order.
  After that, it displays the HANDedness of each crossing.
------------------------------------------------------------------------------
*/
void       k_show(crossings, k)
word       crossings;
crossing  *k;
{
  word   i,
         j;
  word   tab[MAXCROSS];
  dllink  *count,
        *start;

  for (i = 0; i < crossings; i++) tab[i] = 0;
  for (j = 0; j < 2; j++)
  {
    for (i = 0; i < crossings; i++)
    {
      if (k[i].hand && ((tab[i] == 0) || (tab[i] == 1) || (tab[i] == 10)))
      {
        if (tab[i] != 10) count = k[i].o;
        else count = k[i].u;
        start = count;
        if (count != 0) printf("%d ", count->c);
        if (k[count->c].o == count)
        {
          printf("1   ");
          tab[count->c] += 10;
        }
        else
        {
          printf("-1  ");
          tab[count->c] += 1;
        }
        if (count != 0) count = count->z;
        while (count != start)
        {
          printf("%d ", count->c);
          if (k[count->c].o == count)
          {
            printf("1   ");
            tab[count->c] += 10;
          }
          else
          {
            printf("-1  ");
            tab[count->c] += 1;
          }
          count = count->z;
        }
      }
      printf("\n");
    }
  }
  printf("\n");
  for (i = 0; i < crossings; i++)
  {
    if (k[i].hand == 1) printf("%d : right\n", i);
    else if (k[i].hand == (-1)) printf("%d : left\n", i);
  }

  printf("\n");
}




/*
------------------------------------------------------------------------------
  Assumes the file given by the user exists and contains a legal knot.
------------------------------------------------------------------------------
*/
word       k_read(crossings, kk)
word      *crossings;
crossing **kk;
{
  char       name[20];
  word       links,
             startwhere,
             where,
             startover,
             over,
             i,
             j;
  crossing   k[MAXCROSS];
  FILE      *f;

  for (i = 0; i < MAXCROSS; i++) k[i].hand = 0;
  printf("Enter name of knot file: ");
  scanf("%s", name);
  f = fopen(name, "r");
  if (f == 0)
  {
    printf("Can't find %s \n", name);
    fclose(f);
    return FALSE;
  }
  fscanf(f, "%d ", &links);
  for (i=0; i<links; ++i)                    /* how many pieces of string */
  {
    fscanf(f, "%d ", crossings);
    fscanf(f, "%d %d ", &startwhere, &startover);
    if (startover == 1) l_add((dllink *)0, startwhere, &k[startwhere].o);
    else l_add((dllink *)0, startwhere, &k[startwhere].u);
    for (j=1; j<*crossings; ++j)
    {
      fscanf(f, "%d %d ", &where, &over);

      /* check that OVER is legal */
      if ((over != 1) && (over != -1))
      {
        printf("string %d, %th crossing (%d %d), %d is neither 1 nor -1\n",
               i,j,where,over,over);
        return FALSE;
      }
      if (over == 1)
      {
        if (startover == 1) l_add(k[startwhere].o, where, &k[where].o);
        else l_add(k[startwhere].u, where, &k[where].o);
      }
      else
      {
        if (startover == 1) l_add(k[startwhere].o, where, &k[where].u);
        else l_add(k[startwhere].u, where, &k[where].u);
      }
    }
  }
  *crossings = 0;
  while (fscanf(f, "%d %d ", &where, &over) == 2)
  {
    k[where].hand = over;
    if (where > *crossings) *crossings = where;
  }
  (*crossings)++;
  i = fclose(f);
  *kk = (crossing *)malloc(sizeof(crossing)*(*crossings));
  for (i = 0; i < (*crossings); i++) (*kk)[i] = k[i];

  /* check that every crossing has an overpass and underpass */
  for (i = 0; i < (*crossings); i++)
  {
    if (!k[i].o) printf("no overpass  for crossing %d !!!\n",i);
    else if (!k[i].u) printf("no underpass for crossing %d !!!\n",i);
    else if ((k[i].hand != 1) && (k[i].hand != -1))
    {
      printf("crossing %d is neither right or left handed, %d\n",
             i,k[i].hand);
    }
    else continue;
    return FALSE;
  }
  return TRUE;
}