#include <cstdlib>
#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int shift(0);
    char c, shifted_c;
    string text;
    ifstream inputfile("shift-cipher-encoded.txt");
    ofstream outputfile("OUTPUT");
    if (!inputfile) {
        cout << "Could not open input file.\n";
        system("PAUSE");
        exit(1);
    }
    
    if(!getline(inputfile, text, char(0))) exit(1);

    cout << "Hello, enter a shift amount: ";
    cin >> shift;

    for (int i = 0; i < text.length(); i++) {
        c = text[i];    
        if( c >= '0' && c <= '9' ) {
            shifted_c = c - '0';     
            shifted_c += 10 + shift; 
            shifted_c %= 10; 
            shifted_c += '0';        
        } else if (c >= 'a' && c <= 'z') {
            shifted_c = c - 'a';
            shifted_c += 26 + shift;
            shifted_c %= 26; 
            shifted_c += 'a';
        } else if (c >= 'A' && c <= 'Z') {
            shifted_c = c - 'A';
            shifted_c += 26 + shift;
            shifted_c %= 26; 
            shifted_c += 'A';
        } else {
            shifted_c = c;
        }
        outputfile << shifted_c;
    }
    inputfile.close();
    outputfile.close();
    
    cout << "I'm done encrypting your love note. See file OUTPUT. Adios!\n\n";
    
    system("PAUSE");
    return 0;
}