#include <pwd.h>
#include <grp.h>
#include <dirent.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<unistd.h>
#include<time.h>
#include<ctype.h>
#include<string.h>

void dispMode (int);
void scand (char *);

int inode_flag = 0;
int all_flag = 0;
int long_flag = 0;
int rec_flag = 0;

main (int argc, char *argv[])
{
  int n;
  int i, j;
  struct dirent **namelist;
  struct stat buf;
  char dir[30];
  char tempfile[30];

  for (i = 1; i < argc; i++)
    {
      if (argv[i][0] == '-')	//option
	{
	    for (j = 1; j < strlen (argv[i]); j++)
	      {
		if (argv[i][j] == 'l')	//long
		  long_flag = 1;
		else if (argv[i][j] == 'i')	//inode
		  inode_flag = 1;
		else if (argv[i][j] == 'a')	//all files
		  all_flag = 1;
		else if (argv[i][j] == 'r')	//recursive
		  rec_flag = 1;
		else 
		  {
		    printf("ls: invalid option -- %c\n",argv[i][j]);
		    printf("Try \'ls --help\' for more information.\n");
		    exit(0);
		  }
	  }
	}
    }
  if (argc != 1)
    {
      if (argv[argc - 1][0] != '-')	//directory specified
	strcpy (dir, argv[argc - 1]);
      else
	strcpy (dir, ".");	//else current directory
    }
  else
    strcpy (dir, ".");

  scand (dir);

}

//function to display mode in frwxrwxrwx format
void
dispMode (int m)
{
  char mode[11];

  if (m & S_IFREG)		//file
    mode[0] = '-';
  else if (m & S_IFDIR)		//dir
    mode[0] = 'd';
  else if (m & S_IFLNK)		//link
    mode[0] = 'l';
  else if (m & S_IFBLK)		//block
    mode[0] = 'b';
  else if (m & S_IFCHR)		//char
    mode[0] = 'c';
  else if (m & S_IFIFO)		//fifo
    mode[0] = 'f';

//user permissions
  mode[1] = (m & S_IRUSR) ? 'r' : '-';
  mode[2] = (m & S_IWUSR) ? 'w' : '-';
  mode[3] = (m & S_IXUSR) ? 'x' : '-';

//group permissions
  mode[4] = (m & S_IRGRP) ? 'r' : '-';
  mode[5] = (m & S_IWGRP) ? 'w' : '-';
  mode[6] = (m & S_IXGRP) ? 'x' : '-';

//others permissions
  mode[7] = (m & S_IROTH) ? 'r' : '-';
  mode[8] = (m & S_IWOTH) ? 'w' : '-';
  mode[9] = (m & S_IXOTH) ? 'x' : '-';

  mode[10] = '\0';

  printf ("%s", mode);
}

void
scand (char *dir)
{
  int i, n;
  char tempfile[1000];
  struct dirent **namelist;
  struct passwd *pwd;
  struct group *grp;
  struct stat buf;
  char *timestr;
  int j;

  n = scandir (dir, &namelist, 0, alphasort);	//scan directory

  if (n < 0)
    perror ("scandir");
  else
    {
      if (rec_flag)
	printf ("\n%s: \n", dir);
      if (all_flag)		// '-a' option specified
	i = 0;
      else
	i = 2;
      strcat (dir, "/");
      while (i < n)
	{
	  strcpy (tempfile, dir);
	  strcat (tempfile, namelist[i]->d_name);	//path+file
	  stat (tempfile, &buf);
	  if (!all_flag)	// 'a' option not used, ../ should be included
	    if ((namelist[i]->d_name[0] == '.')
		&& (isalnum (namelist[i]->d_name[1])))
	      {
		i++;
		continue;
	      }
	  if (inode_flag)	// '-i' option specified
	    printf ("%7d ", buf.st_ino);
	  if (long_flag)	// '-l' option specified
	    {
	      dispMode (buf.st_mode);	// frwxrwxrwx
	      printf ("%5d ", buf.st_nlink);	//links
	      pwd = getpwuid (buf.st_uid);	//user
	      printf ("%-9s", pwd->pw_name);	//user
	      grp = getgrgid (buf.st_gid);	//group
	      printf ("%-9s", grp->gr_name);	//group
	      printf ("%8d ", buf.st_size);	//file size
	      timestr = ctime (&buf.st_ctime);	//last changed time
	      for (j = 4; j < 16; j++)
		printf ("%c", timestr[j]);
	      printf (" ");
	    }
	  printf ("%s  ", namelist[i]->d_name);	//filename
	  if ((inode_flag && (i + 2) % 3 == 0) || (long_flag))
	    printf ("\n");
	  i++;
	}
      if (rec_flag)
	{
	  if (all_flag)		// '-a' option specified
	    i = 0;
	  else
	    i = 2;
	  while (i < n)
	    {
	      strcpy (tempfile, dir);
	      strcat (tempfile, namelist[i]->d_name);	//path+file
	      stat (tempfile, &buf);
	      if (S_ISDIR (buf.st_mode))
	        {
		  scand (tempfile);
		}  
	      i++;
	    }
	}
      printf ("\n");
      free (namelist);
    }
}