auth.h

//
// Created by Arne Gockeln on 30.07.17.
// Modified by CosminPerRam on 25.04.19.
//

#ifndef AUTH_H
#define AUTH_H

#include <iostream>
#include <libcppotp/otp.h>
#include <ctime>
#include <algorithm>
#include <regex>

namespace auth
{
    uint32_t generateToken(const std::string& t_secret, const int& t_interval = 30) {
        const CppTotp::Bytes::ByteString key = CppTotp::Bytes::fromBase32(t_secret);
        uint32_t token = CppTotp::totp(key, time(nullptr), 0, t_interval, 6);

        return token;
    }

    std::string base32_decode(const std::string& t_base32str) {
        std::string base32_string = t_base32str;
        std::transform(base32_string.begin(), base32_string.end(), base32_string.begin(), ::toupper);
        std::string allowedChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";

        // check for invalid characters
        std::regex regEx("^[ABCDEFGHIJKLMNOPQRSTUVWXYZ234567]+$");
        
        if(!std::regex_match(base32_string, regEx)){
            return "no match";
        }

        const int strLen = base32_string.length();
        int j = 0, n = 0;
        std::string binary;
        for(int i = 0; i < strLen; i++){
            n = n << 5;
            n = n + std::distance(allowedChars.begin(), std::find(allowedChars.begin(), allowedChars.end(), base32_string[i]));
            j += 5;

            if(j >= 8){
                j -= 8;
                char c = (n & ( 0xFF << j ) ) >> j;
                binary += c;
            }
        }

        return binary;
    }
}

#endif