#include <dirent.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/stat.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>

enum { BASE_AMOUNT = 5 };

int
comp(const void *a, const void *b)
{
    const char **str_a = (const char **)a;
    const char **str_b = (const char **)b;
    return strcasecmp(*str_a, *str_b);
}

void
dir_traversal(char *path_root, char *saved_argv)
{
    DIR *root_dir = opendir(path_root), *d;
    if (root_dir == NULL) {
        return;
    }
    struct stat st;
    struct dirent *entry;
    char buf[PATH_MAX];

    int dirs_amount = 0, curr_amount = BASE_AMOUNT;
    char **array = calloc(curr_amount, sizeof(*array));
    while ((entry = readdir(root_dir)) != NULL) {
        if (strlen(path_root) + strlen(entry->d_name) > sizeof(buf) - 1) {
            return;
        }
        snprintf(buf, sizeof(buf), "%s/%s", path_root, entry->d_name);
        if (lstat(buf, &st) == -1) {
            continue;
        }
        if (S_ISDIR(st.st_mode) == 1) {
            if (dirs_amount >= curr_amount-1) {
                curr_amount <<= 1;
                array = realloc(array, curr_amount * sizeof(*array));
            }
            array[dirs_amount++] = strdup(entry->d_name);
        }
    }
    qsort(array, dirs_amount, sizeof(*array), comp);

    closedir(root_dir);
    for (int i = 0; i < dirs_amount; ++i) {
        if (array[i] == NULL) {
            continue;
        }
        if (strcmp(array[i], ".") == 0 || strcmp(array[i], "..") == 0) {
            continue;
        }
        if (strlen(path_root) + strlen(array[i]) > sizeof(buf) - 1) {
            return;
        }
        snprintf(buf, sizeof(buf), "%s/%s", path_root, array[i]);
        if ((d = opendir(buf)) != NULL) {
            closedir(d);
            printf("cd %s\n", array[i]);
            free(array[i]);
            dir_traversal(buf, saved_argv);
        }
    }
    if (strcmp(path_root, saved_argv) != 0) {
        printf("cd ..\n");
    }
    return;
}

int
main(int argc, char *argv[])
{
    dir_traversal(argv[1], argv[1]);

    return 0;
}