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

#include <errno.h>

int main(int argc, char *argv[]){
    char dir_sym[] = "/";
    char source_dir[255], destination_dir[255], temp_dir[255], t_dest_dir[255], t_dest_file[255];

    if (argc < 3){
        printf("need more arguments\n");
        exit(1);
        }

    sprintf(source_dir, "%s%s", argv[1], dir_sym);
    sprintf(destination_dir, "%s%s", argv[2], dir_sym);

    if ( opendir(source_dir) == NULL ){
        printf("error opening source dir\n");
        exit(1);
    }
    if ( opendir(destination_dir) == NULL ){
        printf("error opening destination dir\n");
        exit(1);
    }

    struct dirent **current_dir;
    int number_of_dir_entries;
    number_of_dir_entries = scandir(source_dir, &current_dir, 0, alphasort);
    if (number_of_dir_entries < 0){
        perror("scandir");
        exit(1);
    }

    struct stat dir_entry_stat, dest_file_stat;
    int i, pid, int_for_open;
    int dest_file;
    char shell_cmd[255];
    for (i=0; i<number_of_dir_entries; i++){

        strcpy(temp_dir, source_dir);
        strcat(temp_dir, current_dir[i]->d_name);
        stat(temp_dir, &dir_entry_stat);
        /*****************************************
        if (S_IRUSR&&(dir_entry_stat.st_mode)){
                printf("can't read file\n");
                exit(1);
        }
****************************************************/
        if(S_ISDIR(dir_entry_stat.st_mode)){
            strcpy(t_dest_dir, destination_dir);
            strcat(t_dest_dir, current_dir[i]->d_name);
            free(current_dir[i]);

            if ( opendir(t_dest_dir) == NULL){
                if ( mkdir(t_dest_dir, 0666) !=0){
                    printf("error creating destination directory\n");
                }
            }
            pid=fork();
            if (pid == 0){
                execlp(argv[0], argv[0], temp_dir, t_dest_dir);
                printf("error in execlp\n");
                exit(1);
            }
        }
        if(S_ISREG(dir_entry_stat.st_mode)){

            sprintf(t_dest_file, "%s%s%s", destination_dir, current_dir[i]->d_name, ".gz");

            free(current_dir[i]);

            if ( stat(t_dest_file, &dest_file_stat) == 0 ){
                if (dir_entry_stat.st_mtime > dest_file_stat.st_mtime){
                    sprintf(shell_cmd, "%s%s%s%s", "cp -f ", temp_dir, " ", t_dest_file);
                    system(shell_cmd);
                    sprintf(shell_cmd, "%s%s", "gzip ", t_dest_file);
                    system(shell_cmd);
                }
            }
            else {//если не удалось получить информацию о целевом файле (отсутствует), тогда просто копируем
                sprintf(shell_cmd, "%s%s%s%s", "cp -f ", temp_dir, " ", t_dest_file);
                system(shell_cmd);
                sprintf(shell_cmd, "%s%s", "gzip ", t_dest_file);
                system(shell_cmd);
            }
        }
    }
    free(current_dir);

    return 0;
    }