// 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 <stdlib.h>
#include <time.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "config.h"

/* NCHARS = 10 + 26 + 26 = 62 */
#define NAME_LEN       255
#define NCHARS         62
#define MAX_LEN1       62
#define MAX_LEN2       (62 * 62)
#define MAX_LEN3       (62 * 62 * 62)

/* valid characters for the directory name */
char chars[NCHARS + 1] = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";

/* to store the generated directory name */
char name[NAME_LEN + 1];
int names;
int parent_fd;

/*
 * init_name - initialize the directory name
 *
 * Generate a randomized directory name, and then we generate more
 * directory names based on it.
 */
void init_name(void)
{
       int i;

       srand(time(NULL));

       for (i = 0; i < NAME_LEN; i++)
               name[i] = chars[rand() % 62];
}

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

/*
 * create_dirs - create @names directory names
 * @n: how many names to be created
 *
 * if n <= 62,       we need to modify 1 char of the name
 * if n <= 62*62,    we need to modify 2 chars
 * if n <= 62*62*62, we need to modify 3 chars
 */
void create_dirs(int n)
{
       int i, j, k;
       int depth;

       if (n <= MAX_LEN1)
               depth = 1;
       else if (n <= MAX_LEN2)
               depth = 2;
       else
               depth = 3;

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

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

                       for (k = 0; k < NCHARS; k++) {
                               name[2] = chars[k];
                               create_dir();
                               if (--n == 0)
                                       return;
                       }
               }
       }
}

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

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

       names = atoi(argv[1]);
       if (names > MAX_LEN3 || names <= 0) {
               usage();
               return 1;
       }

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

       init_name();

       create_dirs(names);

       return 0;
}