cipher.cpp

//
//  main.cpp
//  cipher
//
//  Created by Ryan Breaker on 3/14/16.
//  Copyright © 2016 Ryan Breaker. All rights reserved.
//
#include <fstream>
#include <iostream>
#include <string>
using namespace std;


const int NUM_LETTERS = 26;
const int CAESAR = (rand() % (NUM_LETTERS - 1)) + 1;


bool isUpperCase(char c) {
    return (c >= 'A' && c <= 'Z');
}

bool isAlphabetic(char c) {
    return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
}


void encrypt() {
    string line, encrypted = "";
    ifstream inFile("sample.txt");
    ofstream outFile("cipher.txt");

    for(int counter = 0; getline(inFile, line) && counter < 1500; counter++) {
        for(int i = 0; i < line.length(); i++) {
            unsigned char c = line[i];

            if(!isAlphabetic(c)) {
                encrypted += c;
                continue;
            }

            c += CAESAR;

            if(c > 'z' || (isUpperCase(c - CAESAR) && c > 'Z'))
                c -= NUM_LETTERS;

            encrypted += c;
        }

        encrypted += '\n';
    }

    cout << "The encrypted file is:\n";
    cout << encrypted;
    outFile << encrypted;

    outFile.close();
    inFile.close();
}

void decrypt() {
    string decrypted = "";
    ifstream inFile("cipher.txt");
    ofstream outFile("result.txt");

    for(string line; getline(inFile, line); ) {
        for(int i = 0; i < line.length(); i++) {
            unsigned char c = line[i];
            
            if(!isAlphabetic(c)) {
                decrypted += c;
                continue;
            }

            c -= CAESAR;

            if(c < 'A' || (!isUpperCase(c + CAESAR) && c < 'a'))
                c += NUM_LETTERS;

            decrypted += c;
        }

        decrypted += '\n';
    }

    cout << "The decrypted file is:\n";
    cout << decrypted;
    outFile << decrypted;

    outFile.close();
    inFile.close();
}


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

    short choice = 0;
    bool invalidChoice = true;

    //------------------------------
    cout << "STUDENT INFO HERE\n\n";
    //------------------------------


    while(invalidChoice) {
        cout << "Choose your option:\n";
        cout << "1. Encrypt a file\n";
        cout << "2. Decrypt a file\n";
        cout << "Your choice: ";
        cin >> choice;

        if((invalidChoice = (choice < 1 || choice > 2))) {
            cout << "\nInvalid input, please try again.\n";
        }
    }


    if(choice == 1) {
        cout << "You entered option 1 to encrypt file sample.txt\n";
        encrypt();
        return 0;
    }

    decrypt();
    return 0;
}