#include <iostream.h>
#include <iomanip.h>
#include <fstream.h>
#include <conio.h>
#include <ctype.h>


void pause (void) {

  cout << "Hit any key to continue...\n";
  getch ();

}


char get_replacement_character (char ch) {

  if ((ch >= 'a') && (ch <= 'z')) {
    return (char) ('A' + ('z' - ch));
  }
  if ((ch >= 'A') && (ch <= 'Z')) {
    return (char) ('a' + ('Z' - ch));
  }
  if ((ch >= '0') && (ch <= '9')) {
    return (char) ('0' + (((ch - '0') + 5) % 10));
  }
  return ch;

}


void do_processing (ifstream &fin, ofstream &fout) {

  char next_char;
  int line_count = 0, blank_line_count = 0;
  bool current_line_all_blank = true,
       last_char_was_a_newline = true;

  fin >> resetiosflags (ios::skipws);

  for (;;) {

    fin >> next_char;

    if (fin.fail()) { // the read has failed for some reason

      if (fin.eof()) {
        // the read failed because we're at the end of the file.
        // there is nothing more to process - exit the processing loop
        break;
      }

      // the read failed for some other reason.  when reading characters, this
      // is most unlikely, but it is possible.  it could be, for example, that
      // the file being read has been corrupted (physically cannot be read).
      cout << "A file read error has occurred - processing aborted.\n";
      return;

    }

    if (next_char == '\n') { // we're at the end of the current line
      line_count++;
      if (current_line_all_blank) {
        blank_line_count++;
      }
      current_line_all_blank = true; // reset for fresh line
      last_char_was_a_newline = true;
    } else {
      if (!isspace(next_char)) {
        current_line_all_blank = false; // we've seen something
      }
      last_char_was_a_newline = false;
    }

    fout << get_replacement_character (next_char);

  }

  // given an ideal input file, we should always see a newline character just
  // before we reach the end of the file.  if this isn't the case, it means
  // that the last line of the file did not have a newline character.
  if (!last_char_was_a_newline) {
    cout << "\nWarning - the last input line is missing a newline char.\n";
    // do usual end of line processing
    line_count++;
    if (current_line_all_blank) {
      blank_line_count++;
    }
    fout << '\n'; // add missing newline to the output file 
  }

  cout << "\nEncoding complete - the input file contained "
       << line_count << " lines.\n"
       << "Of these, " << blank_line_count << " were completely blank.\n";

}


void main (void) {

  char in_file_name[60], out_file_name[60];
  ifstream fin;
  ofstream fout;

  for (;;) {
    cout << "Enter name of input file: ";
    cin >> in_file_name;
    fin.open (in_file_name);
    if (!fin.fail()) {
      break;
    }
    cout << "Unable to open input file - please try again.\n";
  }

  cout << "Enter name of output file: ";
  cin >> out_file_name;
  fout.open (out_file_name);

  do_processing (fin, fout);

  pause ();

}