// Purpose: copy file
//
// Command syntax:
//   $ ./a.out [ size (>= 0) [ code (>= 0) [ input-file [ output-file ] ] ] ]
// all parameters are optional. Defaults: size=>20, code=>5, input=>cin, output=>cout
//
// Examples:
//   $ ./a.out 34
//   $ ./a.out 34 0
//   $ ./a.out 34 0 in
//   $ ./a.out 34 0 in out

#include <iostream>
#include <fstream>
#include <sstream>
using namespace std;               // direct access to std

bool convert( int &val, char *buffer ) { // convert C string to integer
    std::stringstream ss{ buffer }; // connect stream and buffer
    string temp;
    ss >> dec >> val;               // convert integer from buffer
    return ! ss.fail() &&           // conversion successful ?
    ! ( ss >> temp );               // characters after conversion all blank ?
} // convert

enum { sizeDeflt = 20, codeDeflt = 5 };  // global defaults

int main( int argc, char *argv[] ) {
    unsigned int size = sizeDeflt, code = codeDeflt; // default value
    istream *infile = &cin; // default value, read from stdin
    ostream *outfile = &cout; // default value, write to stdout
    bool error = false;
    string errorMsg;

    switch ( argc ) {
      case 5:
        outfile = new ofstream{ argv[4] };  // open output file
        if ( outfile->fail() ) {
            error = true;
            errorMsg += "could not open output file; ";
        }
        // FALL THROUGH
      case 4:
        infile = new ifstream{ argv[3] };   // open input file
        if ( infile->fail() ) {
            error = true;
            errorMsg += "could not open input file; ";
        }
        // FALL THROUGH
      case 3:
        if ( ! convert( (int &)code, argv[2] ) || (int)code < 0 ) { // invalid integer ?
            error = true;
            errorMsg += "invalid code; ";
        } // if
        // FALL THROUGH
      case 2:
        if ( ! convert( (int &)size, argv[1] ) || (int)size < 0 ) { // invalid integer ?
            error = true;
            errorMsg += "invalid size; ";
        } // if
        // FALL THROUGH
      case 1:                   // all defaults
        break;
      default:                  // wrong number of options
        error = true;
        errorMsg += "wrong number of arguments; ";
    } // switch

    if ( error ) {
        cerr << "Usage: " << argv[0]
             << " [ size (>= 0 : " << sizeDeflt
             << ") [ code (>= 0 : " << codeDeflt
             << ") [ input-file [ output-file ] ] ] ]" << endl;
        cerr << errorMsg << endl;
        return( EXIT_FAILURE );               // TERMINATE
    } // if

    *infile >> noskipws; // turn off white space skipping during input

    char ch;

    // copy input file to output file
    while ( *infile >> ch ) {  // read a character,
        *outfile << ch;        // write a character
    } // while

    if ( infile != &cin ) delete infile;        // close file, do not delete cin!
    if ( outfile != &cout ) delete outfile;     // close file, do not delete cout!
} // main