/** Devin Ashcraft
* Base conversions
* OCCC Fall 2106
* Adv Java
* */

import java.math.BigInteger;
import java.util.Scanner;


public class BaseConvMain {
	public static void main(String[] args){
		Scanner s = new Scanner(System.in); //int scanner
		String originalBase, finalBase;
		int originalNum = 10, finalNum = 0; // for javac
		int i=0;

		//Welcome message
		System.out.println("Welcome to the Base Conversion machine.");

		//Recieves the first Base
		System.out.println("Please enter a string of numbers or letters.");
		originalBase = s.nextLine();

		//removes all spaces from string
		while(i < originalBase.length()){
			char ch = originalBase.charAt(i);
			if( ch == ' '){
				String before = originalBase.substring(0, i);
				String after = originalBase.substring(i + 1);
				originalBase = before + after;
			}
			else {
				i++;
			}
		}

		// Makes sure string is Uppercase
		originalBase = originalBase.toUpperCase();

		// displays base with no spaces
		System.out.println("You entered: " + originalBase + ".");

		// Recieves first base number
		System.out.println("Please enter the value of the initial base.");
		System.out.println("The base is the highest value you entered 0-9, or if using letters highest A-Z");
		originalNum = s.nextInt();
		// Displays num
		System.out.println("The base you entered was: " + originalNum);

		// validate that base and num work together
		ValidateBase(originalNum);
		isValidInteger(originalBase, originalNum);

		// Gets base that we are converting to
		System.out.println("Please enter the base we are converting to (1-36)");
		finalNum = s.nextInt();

		// do conversion
		 finalBase = convertInteger(originalBase, originalNum, finalNum);

		//print finalBase
		System.out.println("The base after conversion is:" + finalBase);
		s.close();
	}

	//Checks that the base entered by user is between 2-36
	private static void ValidateBase(int num){
		if (num < 2 || num > 36){
			System.out.println("Invalid base. Please retry the program.");


			System.exit(0);
		}
	}

	// Checks that the user base works with the given string
	public static boolean isValidInteger(String base, int num){

		char digit;

		for(int i =0; i < base.length(); i++){
			digit = base.charAt(i);
			//Checks if highest digit is not greater than base
			if (Character.isDigit(digit) && (digit - '0') >= num){
				System.out.print("Digit: " +digit + " and Base: " + num + " cannot work together.");
				System.exit(0);
			}

			//checks if highest letter is not greater than base
			else if(Character.isLetter(digit) && (digit - 'A')>= num){
				System.out.print(digit + " and " + num + " cannot work together.");
				System.exit(0);
			}
			//Discards if input isnt 0-9 or A-Z
			else if(!Character.isLetter(digit) && !Character.isDigit(digit)){
				System.out.print("Input is not 0-9, A-Z. Bad input: " + digit);
				System.exit(0);
			}
		}

		return true;
	}

	//Converts original string into user entered base
	// origNum, origBase, newBase
	public static String convertInteger(String base, int num, int finalNum){

		BigInteger decDigit = BigInteger.valueOf(0); // for javac
		BigInteger value = BigInteger.valueOf(0); // for javac
		BigInteger numBI = BigInteger.valueOf(num);
		BigInteger finalNumBI = BigInteger.valueOf(finalNum);
		BigInteger power;

		char digit;



		for (int j = 0; j <base.length(); j++){
			digit = base.charAt(base.length() - 1 - j);

			if(Character.isLetter(digit)){
				decDigit = BigInteger.valueOf(digit - 'A' +10);
			}
			else if(Character.isDigit(digit)){
				decDigit = BigInteger.valueOf(digit - '0');
			}

			value = value.add(decDigit.multiply(numBI.pow(j)));
			//value += decDigit * BigInteger.valueOf(Math.pow((double)num, j));
		}

		int n = 1;

		//for( ; Math.pow(finalNum, n) <= value; n++) {}
		int res = finalNumBI.pow(n).compareTo(value);
		for( ; res >= 0; n++) {}
		char[] result = new char[n];




		for(int k = n-1; k >= 0; k--){


			//power = Math.pow(finalNum, k);
			power = finalNumBI.pow(k);
			//decDigit = Math.floor(value / power);
			decDigit = value.divide(power);
			//value -= decDigit*power;
			value = value.subtract(decDigit.multiply(power));

			int res2 = decDigit.compareTo(BigInteger.valueOf(9));
			if(res2 <= 0){
				result[n-1-k] =(char)('0' + decDigit.intValue());
			}
			else{
				result[n-1-k] =(char)('A' + decDigit.intValue()-10);

			}
			}

		return String.valueOf(result); // returns char array as as string




	}



}