/*
 * Written by Igor Pashev <pashev.igor@gmail.com>
 *
 * The author has placed this work in the Public Domain,
 * thereby relinquishing all copyrights. Everyone is free
 * to use, modify, republish, sell or give away this work
 * without prior consent from anybody.
 *
 */

#include <errno.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <unistd.h>

#ifndef PATH_MAX
#define PATH_MAX 1024
#endif

static int flag_q = 0;
static int flag_d = 0;
static int flag_x = 0;
static int rc;

static struct stat st, st_up;
static const char *path;
static char path_up[PATH_MAX];

static void
usage (void)
{
  fprintf (stderr, "Usage: mountpoint [-q] [-d] [-x] path\n");
  exit (1);
}

static void
xstat (const char *p, struct stat *s)
{
  if (flag_x)
    rc = lstat (p, s);
  else
    rc = stat (p, s);

  if (rc != 0)
    {
      if (!flag_q)
        fprintf (stderr, "mountpoint: %s: %s\n", path, strerror (errno));
      exit (1);
    }
}

int
main (int argc, char *argv[])
{
  while ((rc = getopt (argc, argv, "qdx")) != EOF)
    switch (rc)
      {
      case 'q':
        flag_q++;
        break;
      case 'd':
        flag_d++;
        break;
      case 'x':
        flag_x++;
        break;
      default:
        usage ();
        break;
      }
  if (optind != argc - 1)
    usage ();

  path = argv[optind];
  xstat (path, &st);

  if (flag_x)
    {
      if (S_ISBLK (st.st_mode) || S_ISCHR (st.st_mode))
        {
          printf ("%u:%u\n", major (st.st_rdev), minor (st.st_rdev));
          return 0;
        }
      if (!flag_q)
        fprintf (stderr, "mountpoint: %s: not a block device\n", path);
      return 1;
    }

  if (!S_ISDIR (st.st_mode))
    {
      if (!flag_q)
        fprintf (stderr, "mountpoint: %s: not a directory\n", path);
      return 1;
    }


  rc = snprintf (path_up, sizeof (path_up), "%s/..", path);
  if ((size_t) rc >= sizeof (path_up))
    {
      if (!flag_q)
        fprintf (stderr, "mountpoint: internal error: path is too long: %s\n",
                 path);
      return 1;
    }

  xstat (path_up, &st_up);
  rc = (st.st_dev != st_up.st_dev) || (st.st_dev == st_up.st_dev
                                       && st.st_ino == st_up.st_ino);

  if (flag_d)
    printf ("%u:%u\n", major (st.st_dev), minor (st.st_dev));
  else if (!flag_q)
    printf ("%s is %sa mountpoint\n", path, rc ? "" : "not ");

  return rc ? 0 : 1;
}