/*
 *----------------------------------------------------------------------
 *           "THE BEER-WARE LICENSE" (Revision 42):
 * <jeang3nie@HitchHiker-Linux.org> wrote this file. As long as you
 * retain this notice you can do whatever you want with this stuff. If
 * we meet some day, and you think this stuff is worth it, you can buy
 * me a beer in return.
 * ---------------------------------------------------------------------
 *            ______   _______  _          _________
 *           (  __  \ (  ___  )( (    /|( )\__   __/
 *           | (  \  )| (   ) ||  \  ( ||/    ) (
 *           | |   ) || |   | ||   \ | |      | |
 *           | |   | || |   | || (\ \) |      | |
 *           | |   ) || |   | || | \   |      | |
 *           | (__/  )| (___) || )  \  |      | |
 *           (______/ (_______)|/    )_)      )_(
 *
 *         _______  _______  _       _________ _______
 *        (  ____ )(  ___  )( \    /|\__   __/(  ____ \
 *        | (    )|| (   ) ||  \  ( |   ) (   | (    |/
 *        | (____)|| (___) ||   \ | |   | |   | |
 *        |  _____)|  ___  || (\ \) |   | |   | |
 *        | (      | (   ) || | \   |   | |   | |
 *        | )      | )   ( || )  \  |___) (___| (____|\
 *        |/       |/     \||/    \_)\_______/(_______/
 *
 */

#include <dirent.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

char *__progname;

void usage() {
  printf("Usage: %s [COMMAND]\n", __progname);
  exit(1);
}

int main(int argc, char **argv) {
  char *path, *seg, *__path;
  const char sep[2] = ":";

  __progname = basename(argv[0]);
  if (argc < 2) {
    fprintf(stderr, "%s: Error: missing argument\n", __progname);
    usage();
  } else if (argc > 2) {
    fprintf(stderr, "%s: Error: missing argument\n", __progname);
    usage();
  }
  path = getenv("PATH");
  if (path == NULL) {
    path = "/usr/bin:/bin";
  }
  // Save a copy for later use, since strtok will modify the original
  __path = strndup(path, strlen(path) + 1);
  seg = strtok(path, sep);
  while (seg != NULL) {
    struct dirent *dp;
    DIR *dir = opendir(seg);
    if (dir) {
      while ((dp = readdir(dir)) != NULL) {
        if (strcmp(argv[1], dp->d_name) == 0) {
          char *p = malloc(strlen(argv[1] + strlen(seg) + 2));
          (void)strncpy(p, seg, strlen(seg) + 1);
          (void)strncat(p, "/", 2);
          (void)strncat(p, argv[1], strlen(argv[1]) + 1);
          struct stat path_stat;
          stat(p, &path_stat);
          if (access(p, X_OK) == 0 && S_ISREG(path_stat.st_mode)) {
            printf("%s\n", p);
            exit(0);
          }
        }
      }
    }
    seg = strtok(NULL, sep);
  }
  printf("%s: no %s in (%s)\n", __progname, argv[1], __path);
}