#define _GNU_SOURCE
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

// You may assume that lines are no longer than 1024 bytes
#define LINELEN 1024

static void usage (void);

int
main (int argc, char *argv[])
{
  int opt;
  char *delimitter = " ";
  long field = 1;

  while ((opt = getopt (argc, argv, "d:f:")) != -1)
    {
      switch (opt)
        {
        case 'd':
          delimitter = optarg;
          break;
        case 'f':
          field = strtol (optarg, NULL, 10);
          break;
        default:
          printf ("./bin/cut: invalid option -- \'%c\'\n", optopt);
          exit (EXIT_FAILURE);
        }
    }

  if (field < 1)
    {
      usage ();
      exit (EXIT_FAILURE);
    }

  FILE *file = optind < argc ? fopen (argv[optind], "r") : stdin;
  if (file == NULL)
    {
      perror ("Failed to open input file");
      exit (EXIT_FAILURE);
    }

  char buffer[LINELEN];

  while (fgets (buffer, sizeof (buffer), file) != NULL)
    {
      buffer[strcspn (buffer, "\n")] = '\0';

      char *token = strtok (buffer, delimitter);
      long i = 1;
      while (i++ < field) token = strtok (NULL, delimitter);

      printf("%s\n", token != NULL ? token : "");
    }

  return EXIT_SUCCESS;
}

static void
usage (void)
{
  printf ("cut, splits each line based on a delimiter\n");
  printf ("usage: cut [FLAG] FILE\n");
  printf ("FLAG can be:\n");
  printf (
      "  -d C     split each line based on the character C (default ' ')\n");
  printf ("  -f N     print the Nth field (1 is first, default 1)\n");
  printf ("If no FILE specified, read from STDIN\n");
}