//Base translator
//Author: Sam Barba
//Created 12/11/2017

package baseConverter;
import java.util.Scanner;

public class BaseConverter {
    public static String baseConvert(int baseFrom, String number, int baseTo) {
        //converting <number> first to decimal from base <baseFrom>
        double decNum = 0; //doubles are used so big numbers can be processed
        int actualBit = 0;

        for (int i = 0; i < number.length(); i++) {
            char bit = number.charAt(i);

            if ((char) bit >= 65) //if bit is A, B, C etc.
                actualBit = ((int) bit) - 65 + 10; //convert bit to numeric value (A = 10, B = 11...)
            else if (bit > 0)
                actualBit = Character.getNumericValue(bit);

            decNum += Math.pow(baseFrom, (number.length() - i - 1)) * actualBit;
        }

        //converting decimal version to base <baseTo>
        String reverseRemaindersStr = "";

        while (decNum > 0) {
            double remainder = decNum % baseTo;

            if (remainder >= 10)
                reverseRemaindersStr += (char) (65 + (remainder - 10)); //converts remainder to A, B or C etc. if >= 10 (A = 65 in ASCII)
            else
                reverseRemaindersStr += Integer.toString((int) remainder);

            decNum = Math.floor(decNum / baseTo);
        }

        //the remainders string needs to be reversed
        if (reverseRemaindersStr.length() > 0) {
            String remaindersStr = "";
            if (baseTo != 10)
                for (int i = reverseRemaindersStr.length() - 1; i >= 0; i--)
                    remaindersStr += reverseRemaindersStr.charAt(i);
            else { //add commas to separate it into groups of 3 digits (only in base 10)
                for (int i = reverseRemaindersStr.length() - 1; i >= 0; i--) {
                    remaindersStr += reverseRemaindersStr.charAt(i);
                    if (i % 3 == 0 && i > 0)
                        remaindersStr += ",";
                }
            }

            return remaindersStr;
        }

        return "0";
    }

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        char repeat = 'C';

        while (repeat == 'C') {
            System.out.print("Enter the base you're converting from (2 - 36): ");
            int baseFrom = input.nextInt();
            System.out.print("Enter the number in base " + baseFrom + ": ");
            String number = input.next().toUpperCase();
            System.out.print("Enter the base you're converting to (2 - 36): ");
            int baseTo = input.nextInt();

            System.out.println();
            System.out.println(number + " in base " + baseFrom + " = " + baseConvert(baseFrom, number, baseTo) + " in base " + baseTo);

            System.out.println();
            System.out.print("Enter C to continue or another char to exit: ");
            repeat = input.next().toUpperCase().charAt(0);
            System.out.println();
        }
    }
}