//Problem 7. One system to any other

//Write a program to convert from any numeral system of given base s to any other numeral system of base d (2 ≤ s, d ≤ 16).

using System;
using System.Text;

class OneSystemToAny
{
    static void Main()
    {
        string task = "Problem 7. One system to any other\n\nWrite a program to convert from any numeral system of given base s to any\nother numeral system of base d (2 ≤ s, d ≤ 16).\n";

        string separator = new string('*', Console.WindowWidth);

        Console.WriteLine(task);
        Console.WriteLine(separator);

        Console.Write("Enter base to convert from: ");
        uint fromBase = uint.Parse(Console.ReadLine());

        Console.Write("Enter base to convert to: ");
        uint toBase = uint.Parse(Console.ReadLine());

        Console.WriteLine("Enter positive number: ");
        string number = Console.ReadLine();

        Console.WriteLine("\nNumber in {0} base: {1}",toBase, ConvertAnyToAny(number,fromBase,toBase));
    }

    private static string ConvertAnyToAny(string number, uint fromBase, uint toBase)
    {
        return DecimalToAny(AnyToDecimal(number, fromBase), toBase);
    }

    private static ulong AnyToDecimal(string number, uint baseSystem)
    {
        ulong result = 0;

        for (int i = number.Length - 1; i >= 0; i--)
        {
            uint CurrentNumber = (uint)(char.IsDigit(number[i]) ? number[i] - '0': number[i] - 'A' + 10);
            int pow = number.Length - i - 1;
            result += CurrentNumber * (ulong)Math.Pow(baseSystem, pow);
        }

        return result;
    }

    private static string DecimalToAny(ulong number, uint baseSystem)
    {
        StringBuilder result = new StringBuilder();

        do
        {
            int numberToAdd = (int)(number % baseSystem);
            result.Insert(0, (char)(numberToAdd <= 9 ? numberToAdd + '0': 'A' + numberToAdd - 10));
            number /= baseSystem;
        } while (number > 0);

        return result.ToString();
    }
}