#include "pch.h"
#include <iostream>
#include <string>

using std::string;
using std::endl;
using std::cout;
using std::cin;

// Uppercase letters only
string DecimalToBase(int number, int base) {
    string pattern = "0123456789ABCDEFGHIJKLMOPQRSTUVWXYZ";
    string result = "";

    while (number) {
        result = pattern[number % base] + result;
        number /= base;
    }
    return result;
}

int handleHelp(char c) {
    if (c >= 'A' & c <= 'Z')
        return c - 55;
    else if (c >= '0' && c <= '9')
        return  c - 48; // '0';
    else return -1;
}

// Using Horner's method
// returns - 1 when error occurs
int BaseToDecimal(string number,  int size, int curr_base) {
    int result = handleHelp(number[0]);
    if(handleHelp(number[0]) < 0) return -1;
    for (int i = 1; i < size; i++) {
        if(handleHelp(number[i]) < 0) return -1;
        result = result * curr_base + handleHelp(number[i]);
    }
    return result;
}

int main()
{
    cout << "Program do zamiany systemow pozycyjnych.\n";
    int number, base;
    cout << "Podaj liczbe do zamiany: ";
    cin >> number;
    cout << "Podaj podstawe nowego systemu: ";
    cin >> base;

    string res = DecimalToBase(number, base);

    cout << "Liczba - " << number << " - w systemie o podstawie - " << base << " - wynosi: ";
    cout << res << endl;

    cout << "Twoja liczba to w systemie dziesietnym - " << BaseToDecimal(res, res.size(), base) << endl;
}