/*
 * UNG's Not GNU
 * 
 * Copyright (c) 2011-2014, Jakob Kaivo <jakob@kaivo.net>
 * 
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 */

#include <stdio.h>
#include <pwd.h>
#include <grp.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

const char *id_desc = "return user identity";
const char *id_inv  = "id [user]\nid -G [-n] [user]\nid -g [-nr] user\nid -u [-nr] [user]";

#define FULL	0
#define NAMES	1
#define NUMS	2

void id_printgids (char *user, int mode)
{
  struct group *gr = NULL;
  struct group *current = NULL;
  int num_groups = 0;
  char sep = ' ';
  int i = 0;

  setgrent();
  while ((current = getgrent()) != NULL) {
    for (i = 0; current->gr_mem[i] != NULL; i++) {
      if (!strcmp (user, current->gr_mem[i])) {
        num_groups++;
        gr = realloc (gr, num_groups * sizeof(struct group));
	gr[num_groups-1].gr_gid = current->gr_gid;
        gr[num_groups-1].gr_name = strdup (current->gr_name);
      } 
    }
  }
  endgrent();

  if (mode == FULL && num_groups > 0) {
    printf (" groups=");
    sep = ',';
  }

  while (i < num_groups) {
    if (i > 0)
      putchar (sep);
    switch (mode) {
      case NAMES:
        printf ("%s", gr[i].gr_name);
        break;
      case NUMS:
        printf ("%u", gr[i].gr_gid);
        break;
      default:
        printf ("%u(%s)", gr[i].gr_gid, gr[i].gr_name);
        break;
    }
    free (gr[i].gr_name);
    i++;
  }
  free (gr);
}

int
main (int argc, char **argv)
{
  int n = 0, r = 0;
  char mode = 0;
  int c;
  struct passwd pw;
  struct group gr;

  while ((c = getopt (argc, argv, ":Ggunr")) != -1) {
    switch (c) {
      case 'G':
      case 'g':
      case 'u':
        if (mode)
          return 1;
        mode = c;
        break;
      case 'n':
        n = 1;
        break;
      case 'r':
        r = 1;
        break;
      default:
        return 1;
    }
  }

  if ((mode == 0 && (n == 1 || r == 1)) || (mode == 'G' && r == 1))
    return 1;
  
  if (optind >= argc)
    pw = *getpwuid (mode == 'u' && r == 0 ? geteuid() : getuid());
  else if (optind == argc -1)
    pw = *getpwnam (argv[optind]);
  else
    return 1;

  switch (mode) {
    case 'G':
      id_printgids (pw.pw_name, n ? NAMES : NUMS);
      break;
    case 'g':
      gr = *getgrgid (r ? getgid() : getegid());
      if (n) printf ("%s", gr.gr_name);
      else printf ("%u", gr.gr_gid);
      break;
    case 'u':
      if (n) printf ("%s", pw.pw_name);
      else printf ("%u", pw.pw_uid);
      break;
    default:
      gr = *getgrgid (pw.pw_uid == getuid() ? getgid() : pw.pw_gid);
      printf ("uid=%u(%s) gid=%u(%s)", pw.pw_uid, pw.pw_name, gr.gr_gid, gr.gr_name);
      if (pw.pw_uid != geteuid()) {
        pw = *getpwuid (geteuid());
        printf (" euid=%u(%s)", pw.pw_uid, pw.pw_name);
      }
      if (gr.gr_gid != getegid()) {
        gr = *getgrgid (getegid());
        printf (" egid=%u(%s)", gr.gr_gid, gr.gr_name);
      }
      id_printgids (pw.pw_name, FULL); 
  }
  printf ("\n");
  return 0;
}