#include "header.h"

void printerror(char *errmsg1, char *errmsg2)
{
  strcat(errmsg1, errmsg2);
  perror(errmsg1);
}

void print_usage(char *arg)
{
  fprintf(stderr, "USAGE: \n\t %s [input] [-o output]\n", arg);
  exit(1);
}

struct args parse_input(int argc, char *argv[])
{
  struct args these_args;
  int i;
  boolean input_init = FALSE;
  boolean output_init = FALSE;
  boolean num_of_lines_init = FALSE;
  for(i = 1; i < argc; i++)
  {
    char *cur_arg = *(argv+i);
    if(cur_arg[0] == '-')
    {
      if(cur_arg[1] == 'o')
      {
      /* open for writing the name following -o */
      these_args.output_fd = creat(argv[i+1], 0644);
      if(these_args.output_fd < 0)
      {
	printerror("can't open ", argv[i+1]);
      }
      /* increment i to skip through the argument past -o */
      i++;
      output_init = TRUE;
      }
      else
      {
	these_args.num_of_lines = cur_arg;
	num_of_lines_init = TRUE;
      }
    }
    else
    { /* must be the input file */
    /* in the case that the input file was already specified */
    if(input_init)
    {
      print_usage(argv[0]);
    }
    these_args.input_fd = open(cur_arg, O_RDONLY);
    if(these_args.input_fd < 0)
    {
      printerror("can't open ", cur_arg);
    }
    input_init = TRUE;
    }
  }
  if(!input_init)
  {
    these_args.input_fd = 0;
  }
  if(!output_init)
  {
    these_args.output_fd = 1;
  }
  if(!num_of_lines_init)
  {
    these_args.num_of_lines = "";
  }
  return these_args;
}