// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (c) 2009 FUJITSU LIMITED
 * Author: Li Zefan <lizf@cn.fujitsu.com>
 */

#define _POSIX_C_SOURCE 200809L
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "config.h"

/* NCHARS = 10 + 26 + 26 = 62 */
#define NCHARS      62
#define MAX_LEN1    62
#define MAX_LEN2    (62 * 62)
#define MAX_LEN3    (62 * 62 * 62)
#define MAX_NAMES   (MAX_LEN1 + MAX_LEN2 + MAX_LEN3)

/* valid characters for a directory name */
char chars[] = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";

/* to store the generated directory name */
char name[10];
int names;
int parent_fd;

void create_dir(void)
{
       if (mkdirat(parent_fd, name, S_IRWXU)) {
               perror("mkdir");
               exit(1);
       }
}

/*
 * create_1 - create length-1 directory names
 * @n: how name names to be created
 */
void create_1(int n)
{
       int i;

       name[1] = '\0';
       for (i = 0; i < NCHARS; i++) {
               name[0] = chars[i];
               create_dir();
               if (--n == 0)
                       return;
       }
}

/*
 * create_2 - generate length-2 directory names
 * @n: how many names to be created
 */
void create_2(int n)
{
       int i, j;

       name[2] = '\0';
       for (i = 0; i < NCHARS; i++) {
               name[0] = chars[i];
               for (j = 0; j < NCHARS; j++) {
                       name[1] = chars[j];
                       create_dir();
                       if (--n == 0)
                               return;
               }
       }
}

/*
 * create_3 - generate length-3 directory names
 * @n: how many names to be created
 */
void create_3(int n)
{
       int i, j, k;

       name[3] = '\0';
       for (i = 0; i < NCHARS; i++) {
               name[0] = chars[i];
               for (j = 0; j < NCHARS; j++) {
                       name[1] = chars[j];
                       for (k = 0; k < NCHARS; k++) {
                               name[2] = chars[k];
                               create_dir();
                               if (--n == 0)
                                       return;
                       }
               }
       }
}

void usage()
{
       fprintf(stderr, "Usage: create_short_dirs nr_dirs parent_dir\n");
}

/*
 * Create short-name directoriess
 * @argv[1]: director number
 * @argv[2]: the parent directory
 */
int main(int argc, char *argv[])
{
       if (argc != 3) {
               usage();
               return 1;
       }

       names = atoi(argv[1]);
       if (names > MAX_NAMES || names <= 0) {
               usage();
               return 1;
       }

       parent_fd = open(argv[2], O_RDONLY);
       if (parent_fd == -1) {
               perror("open parent dir failed");
               return 1;
       }

       create_1(names);
       if (names <= MAX_LEN1)
               return 0;

       names -= MAX_LEN1;
       create_2(names);
       if (names <= MAX_LEN2)
               return 0;

       names -= MAX_LEN2;
       create_3(names);

       return 0;
}