#include "graph/adj.h"
#include <errno.h>
#include <stdlib.h>

struct graph *
new_graph (unsigned int nv)
{
  struct graph *g;

  if (!nv)
    {
      errno = EINVAL;
      return NULL;
    }

  if (!(g = malloc (sizeof *g)))
    return NULL;

  g->nv = nv;

  if (!(g->v = calloc (nv, sizeof *g->v)))
    {
      free (g);
      return NULL;
    }

  return g;
}

int
new_arc (struct graph *g, unsigned int vi, unsigned int vj)
{
  struct edge *e;

  if (vi >= g->nv || vj >= g->nv)
    return -(errno = EINVAL);

  if (!(e = malloc (sizeof *e)))
    return -errno;

  e->to = &g->v[vj];
  e->next = g->v[vi].adj;
  g->v[vi].adj = e;

  return 0;
}

int
new_edge (struct graph *g, unsigned int vi, unsigned int vj)
{
  int err;

  if (vi == vj)
    return -(errno = EINVAL);

  if ((err = new_arc (g, vi, vj)))
    return err;

  if ((err = new_arc (g, vj, vi)))
    return err;

  return 0;
}