#include <stdio.h>
#include <stdlib.h>

void
help(char *name)
{
  fprintf (stderr, "Usage: %s [-v] [-o OFILE] [-c CHARS] FILE1 ... FILEn\n", name);
  fprintf (stderr, "Write some characters to OFILE (or standard output)\n");
  fprintf (stderr, "  -v : Verbose mode\n");
  fprintf (stderr, "  -o OFILE : select output file\n");
  fprintf (stderr, "  -c CHARS : select number of characters to read per input file\n");
}

int
main (int argc, char *argv[])
{
  char *outfile = NULL;
  int chars = 1;
  int verbose = 0;
  char *files[argc];
  int numfiles = 0;

  // Set up the list of input files
  for (int i = 0; i < argc; i++)
    {
      files[i] = (char *) 0;
    } // for

  // Process the command line
  for (int i = 1; i < argc; i++)
    {
      if (argv[i][0] == '-')
        {
          char flag = argv[i][1];
          switch (flag)
            {
              case 'v':
                verbose = 1;
                break;
              case 'o':
                if (argv[i][2] == 0)
                  {
                    outfile = argv[++i];        // Ugh
                  }
                else
                  {
                    outfile = argv[i] + 2;
                  }
                break;
              case 'c':
                if (argv[i][2] == 0)
                  {
                    chars = atoi (argv[++i]);
                  } 
                else
                  {
                    chars = atoi (argv[i] + 2);
                  }
                break;

              case 'h':
                help (argv[0]);
                exit (EXIT_SUCCESS);
                break;

              default:
                fprintf (stderr, "Invalid flag: '%s'\n", argv[i]);
                help (argv[0]);
                exit (EXIT_FAILURE);
                break;
            } // switch
        } // if we have a dash
      else if (argv[i][0] == 0)
        {
          fprintf (stderr, "Empty strings not permitted.\n");
          help (argv[1]);
          exit (EXIT_FAILURE);
        }
      else
        {
          files[numfiles++] = argv[i];
        } // if we don't have a dash
    } // for

  if (verbose)
    {
      fprintf (stderr, "Verbose mode on.\n");
      fprintf (stderr, "Characters to copy: %d\n", chars);
      fprintf (stderr, "Files to use: %d\n", numfiles);
      if (outfile)
        {
          fprintf (stderr, "Printing output to %s\n", outfile);
        }
      else
        {
          fprintf (stderr, "Printing output to stdout.\n");
        } 
    } // if (verbose)

  // Prepare output
  FILE *target = stdout;
  if (outfile)
    {
      target = fopen (outfile, "w");
    }

  // Copy characters
  for  (int i = 0; i < numfiles; i++)
    {
      if (verbose)
        {
          fprintf (stderr, "Copying from %s\n", files[i]);
        } // if verbose
      FILE *source = fopen (files[i], "r");
      for (int ch = 0; ch < chars; ch++)
        {
          putc (getc (source), target);
        } // for ch
      fclose (source);
    } // for i

  // Clean up
  if (outfile)
    {
      fclose (target);
    }
    

  exit (EXIT_SUCCESS);
} // main