#include <iostream>

#include <string>

#include <fstream>

const char lowerrange = 'z' - 'a';

const char upperrange = 'Z' - 'A';

char encode_char( const char & c, int rotation )

{

char result = c;

if( c >= 'a' && c <= 'z' )

{

result -= 'a';

result += rotation;

result %= lowerrange;

result += 'a';

}

else if ( c >= 'A' && c <= 'Z' )

{

result -= 'A';

result += rotation;

result %= upperrange;

result += 'A';

}

return result;

}

std::string encode( std::string cleartext, int rotation )

{

std::string ciphertext = "";

for( auto c = cleartext.begin(); c != cleartext.end(); ++c )

{

ciphertext += encode_char( *c, rotation );

}

return ciphertext;

}

int main( int argc, char *argv[] )

{

if( argc < 4 )

{

std::cerr << "not enough arguments; usage; caeser_encode [path_to_cleartext] [rotation] [path_to_output_file]" << std::endl;

return 1;

}

std::fstream cleartext_file( argv[1] );

if( !cleartext_file.is_open() )

{

std::cerr << "couldn't open file for reading: " << argv[1] << std::endl;

return 1;

}

std::fstream ciphertext_file;

ciphertext_file.open( argv[3], std::fstream::out );

if( !ciphertext_file.is_open() )

{

std::cerr << "couldn't open file for writing: " << argv[3] << std::endl;

return 1;

}

int rotation = std::stoi( argv[2] );

if( rotation < 1 || rotation > 25 )

{

std::cerr << "provide a rotation from 1 to 25" << std::endl;

return 1;

}

std::string ciphertext = "";

std::string line = "";

while( getline( cleartext_file, line ) )

{

ciphertext_file << encode( line, rotation ) << std::endl;

}

std::cout << ciphertext << std::endl;

return 0;

}