#include <errno.h>
#include <sys/types.h>
#include <dirent.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
// strlen
#include <string.h>
// malloc
#include <stdlib.h>
//DIR *opendir(const char *name);
//DIR *fdopendir(int fd);
//int fstatat(int dirfd, const char *pathname, struct stat *buf,
//            int flags);


int list(int dirfd, char* curdir,int length){
    char* next_curdirnext = NULL;
    int next_length = 0;
//    putchar
    
    DIR* pdir = fdopendir(dirfd);
    if(pdir==NULL){
        perror("fehler fopendir");
        return 1;
    }   
    struct dirent * pdirent = NULL;  
    struct stat statbuf;
    while(1)
    {
        errno = 0; 
        pdirent = readdir(pdir);
        if(pdirent==NULL){
            if(errno==0)
            {
//                printf("end reached\n");
                closedir(pdir);        
                break;
            }
            else
            {
                fprintf(stderr," readdir errno = %d\n",errno);
                return 1; 
            }
        }
        else
        {
            if(pdirent->d_name[0]=='.'){
                if(pdirent->d_name[1]==0){
                    //printf("ignore SELF\n");
                    continue;
                }
                if(pdirent->d_name[1]=='.'){
                    if(pdirent->d_name[2]==0){
                     //   printf("ignore PARENT\n");
                        continue;
                    }
                }
            }
            if( 0== fstatat(dirfd,pdirent->d_name,&statbuf,AT_SYMLINK_NOFOLLOW) )
            {
                printf("%s/%s\n",curdir,pdirent->d_name);
                if(S_ISDIR(statbuf.st_mode)){
               //     printf("%s\n",pdirent->d_name);
                    int subdirfd = openat(dirfd,pdirent->d_name,O_RDONLY); 
                    if(-1 == subdirfd)
                    {
                        perror("subdirfd");
                    } else {
                        next_length=(length+1+strlen(pdirent->d_name));
                        next_curdirnext = malloc(next_length);
                        if(next_curdirnext==NULL)
                        {
                            perror("malloc");
                        } 
                        else 
                        {
                            sprintf(next_curdirnext,"%s/%s",curdir,pdirent->d_name);
                            list(subdirfd,next_curdirnext,next_length);
                            free(next_curdirnext);
                            close(subdirfd);
                        }
                    }
                } 
                //else
                //{
                ////    printf("%s/%s\n",curdir,pdirent->d_name);
                //}
                   //struct stat {
                   //    dev_t      st_dev;      /* ID of device containing file */
                   //    ino_t      st_ino;      /* Inode number */
                   //    mode_t     st_mode;     /* File type and mode */
                   //    nlink_t    st_nlink;    /* Number of hard links */
                   //    uid_t      st_uid;      /* User ID of owner */
                   //    gid_t      st_gid;      /* Group ID of owner */
                   //    dev_t      st_rdev;     /* Device ID (if special file) */
                   //    off_t      st_size;     /* Total size, in bytes */
                   //    blksize_t  st_blksize;  /* Block size for filesystem I/O */
                   //    blkcnt_t   st_blocks;   /* Number of 512 B blocks allocated */

                   //    /* Since POSIX.1-2008, this structure supports nanosecond
                   //       precision for the following timestamp fields.
                   //       For the details before POSIX.1-2008, see VERSIONS. */

                   //    struct timespec  st_atim;  /* Time of last access */
                   //    struct timespec  st_mtim;  /* Time of last modification */
                   //    struct timespec  st_ctim;  /* Time of last status change */

                   //#define st_atime  st_atim.tv_sec  /* Backward compatibility */
                   //#define st_mtime  st_mtim.tv_sec
                   //#define st_ctime  st_ctim.tv_sec
                   //}; 
            }
            else
            {
                fprintf(stderr,"fstatat errno = %d\n",errno);
                return 2; 
            }
            //printf("%d %s\n",pdirent->d_type ,pdirent->d_name);
        }
    } 
//    printf("dirfd = %d %p\n",dirfd,pdir);
    return 0;
}


int main(int argc, char* argv[]){
//    DIR current;
    int dirfd;
    char* curdir= "."; 
    puts(".");
    dirfd = openat(AT_FDCWD,".",O_RDONLY); 
    if (dirfd > -1){
        list(dirfd,curdir,1+strlen(curdir));
    }
    return 0;
}