using System;

public class Core
{

    public static string ConvertTo(int value, int newBase)
    {
        string Chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        string result = "";
        int remainder = 0;      //the rest from dividing

        if (value == 0)
            return "0";

        while (value > 0)
        {
            result = Chars[value % newBase] + result;
            Console.WriteLine("\t\t"+value + "\t/\t" + newBase + " | " + result[remainder]);
            value /= newBase;
        }
        return result;
    }

    public static int ConvertFrom(string number, int oldBase)
    {
        const int ASCII_LETTER_TO_VALUE = 55;
        const int ASCII_DIGIT_TO_VALUE = 48;
        int power = 0;
        int sum = 0;

        foreach (char digit in number)
        {
            if (!(char.IsUpper(digit) || char.IsDigit(digit)))
                throw new Exception($"Character {digit} is out of conversion range! Use digits or upper letters.");

            int digitValue = char.IsDigit(digit) ? digit - ASCII_DIGIT_TO_VALUE : digit - ASCII_LETTER_TO_VALUE;

            if (digitValue > (oldBase - 1))
                throw new Exception($"Digit value: {digitValue} is greater than numeric base!");

            sum = sum + ((int)Math.Pow(oldBase, power) * digitValue);

            Console.WriteLine($"\t\t | {oldBase} ^ {power} * {digit} = {Math.Pow(oldBase, power) * digitValue} \t||{sum}");

            power = power + 1;
        }
        Console.WriteLine("\t\n\nWynik pośredni, dziesiętnie: {0}\n\n",sum);

        return sum;
    }
    public static void Input(int firstBase, int secondBase)
    {
        Console.Clear();
        Console.WriteLine("\n\nPodaj liczbę w systemie "+ firstBase +"-owym do przeliczenia: ");
        String nvalue = Console.ReadLine();
        int jeden = ConvertFrom(nvalue, firstBase);
        string dwa = ConvertTo(jeden, secondBase);
        Console.WriteLine();
        Console.WriteLine();
        Console.WriteLine(dwa);
    }
    public static void Main()
    {

        bool status = false;
        while (!status)
        {
            Console.WriteLine("\nPrzelicznik systemów liczbowych obejmujący system trójkowy i siódemkowy");
            Console.WriteLine("\n\n\t1 - Z trójkowego na siódemkowy.\n\t2 - Z siódemkowego na trójkowy.\n\t3 - Koniec programu.");
            ConsoleKeyInfo button = Console.ReadKey();
            switch (button.Key)
            {
                case ConsoleKey.D1:
                    Input(3, 7);
                    break;
                case ConsoleKey.D2:
                    Input(7, 3);
                    break;
                case ConsoleKey.D3:
                    status = true;
                    break;
                default:
                    Console.WriteLine("\nNieprawidłowy wybór");
                    break;
            }
        }
    }
}