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

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

  DIR *src_dir = NULL;
  DIR *dst_dir = NULL;
  DIR *inner_dir = NULL;
  FILE *src_file = NULL;
  const char *src_dirname = NULL;
  const char *dst_dirname = NULL;
  char *dst_gz_filename = NULL;
  char *dst_filename = NULL;
  char *src_filename = NULL;
  char *command = NULL;
  char *current_dir = (char *)getcwd(NULL,0);
  struct dirent *src_ent;
  struct stat src_st;
  struct stat dst_st;
  int file_counter = 0;

   if (argc < 3)
  {
    printf("Two parameters nedeed: SOURCE_DIR DEST_DIR\n");
    return 1;
  }

   //cutting possible '/' at the end of arguments
   if ('/' == argv[1][strlen(argv[1]) - 1])   argv[1][strlen(argv[1]) - 1] = 0;
   if ('/' == argv[2][strlen(argv[2]) - 1])   argv[2][strlen(argv[2]) - 1] = 0;
   src_dirname = argv[1];
   dst_dirname = argv[2];

   if (NULL == (src_dir = opendir(src_dirname)))
    {
      perror(src_dirname);
      return 2;
    }
   if (NULL == (dst_dir = opendir(dst_dirname)))
    {
      perror(dst_dirname);
      return 3;
    }
    closedir(dst_dir);

   // get full paths
   chdir(src_dirname);
   src_dirname = (char *)getcwd(NULL,0);
   chdir(current_dir);
   chdir(dst_dirname);
   dst_dirname = (char *)getcwd(NULL,0);
   chdir(current_dir);


   while(NULL != (src_ent = readdir(src_dir)))
    {
        if ((!strcmp(src_ent->d_name,".")) || (!strcmp(src_ent->d_name,"..")))
    {
      continue;
    }
    src_filename = malloc(strlen(src_ent->d_name) + strlen(src_dirname) + 10);
    sprintf(src_filename, "%s/%s", src_dirname, src_ent->d_name);

    dst_filename = malloc(strlen(src_ent->d_name) + strlen(dst_dirname) + 10);
    sprintf(dst_filename, "%s/%s", dst_dirname, src_ent->d_name);

    dst_gz_filename = malloc(strlen(dst_filename) + 10);
    sprintf(dst_gz_filename, "%s.gz", dst_filename);

    if (DT_DIR == src_ent->d_type)
    {
      // Its a directory
      if (NULL != (inner_dir = opendir(src_filename)))
      {
        closedir(inner_dir);
        if (-1 == stat(dst_filename, &dst_st))
        {
            command = malloc(strlen(dst_filename) + 10);
        sprintf(command, "mkdir %s", dst_filename);
        if (-1 == system(command))
        {
          printf("Cannot execute command:%s\n", command);
          return 5;
        }
        //printf("Execute command:%s\n", command);
        free(command);
        }
        //recursion
        command = malloc(strlen(argv[0]) + strlen(src_filename) + strlen(dst_filename) + 10);
        sprintf(command, "%s %s %s", argv[0], src_filename, dst_filename);
        if (-1 == system(command))
        {
        printf("Cannot execute command:%s\n", command);
        return 5;
        }
        //printf("Execute command:%s\n", command);
        free(command);
      }
      else
      {
        perror(src_filename);
        continue;
      }
    }
    if (DT_REG == src_ent->d_type)
    {

      if (-1 == stat(src_filename, &src_st))
      {
        perror(src_filename);
        continue;
      }
      else
      {
        if (-1 != stat(dst_gz_filename, &dst_st))
        {
          // archive file is present
          if (src_st.st_mtime > dst_st.st_mtime)
          {
          // rm dst_gz_filename
        command = malloc(strlen(dst_gz_filename) + 10);
        sprintf(command, "rm %s", dst_gz_filename);
        if (-1 == system(command))
        {
          printf("Cannot execute command:%s\n", command);
          return 5;
        }
        //printf("Execute command:%s\n", command);
        free(command);
          }
          else
          {
        continue;
          }
        }
        // archive file is absent
        // cp src_filename dst_filename
        command = malloc(strlen(src_filename) + strlen(dst_filename) + 10);
        sprintf(command, "cp %s %s", src_filename, dst_filename);
        if (-1 == system(command))
        {
          printf("Cannot execute command:%s\n", command);
          return 5;
        }
       // printf("Execute command:%s\n", command);
        // gzip dst_filename
        sprintf(command, "gzip %s", dst_filename);
        if (-1 == system(command))
        {
          printf("Cannot execute command:%s\n", command);
          return 5;
        }
        //printf("Execute command:%s\n", command);
        file_counter++;
        free(command);
      }
     }
     free(dst_gz_filename);
     free(src_filename);
     free(dst_filename);
    }

  closedir(src_dir);
  free(current_dir);
  if (file_counter)
  {
    printf("%d files backuped!\n", file_counter);
  }
  return 0;
}