/*
    BaseConverter.java
    Dave Klick
    CIS 160
    2014-09-11
 
    Converts a number between bases using command line arguments.
*/ 

import java.util.Scanner;
import java.util.HashMap;

public class BaseConverter {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int baseFrom = 10, baseTo = 10, number = 0;
        HashMap<Character, String> map = new HashMap<Character, String>() {{
            put('0', "0000"); put('1', "0001"); put('2', "0010"); put('3', "0011"); 
            put('4', "0100"); put('5', "0101"); put('6', "0110"); put('7', "0111"); 
            put('8', "1000"); put('9', "1001"); put('A', "1010"); put('B', "1011"); 
            put('C', "1100"); put('D', "1101"); put('E', "1110"); put('F', "1111"); }};
        
        if (args.length != 3) {
            System.err.println("Usage: java BaseConverter number baseFrom baseTo");
            System.exit(1);
        }
        
        try {
            baseFrom = Integer.parseInt(args[1], 10);
            if (baseFrom < 2 || baseFrom > 16) throw new NumberFormatException("Base out of Range");
        } catch (NumberFormatException e) {
            System.err.println("Invalid base to convert from: " + args[1]);
            System.exit(2);
        }
        
        try {
            baseTo = Integer.parseInt(args[2], 10);
            if (baseTo != 2 && baseTo != 8 && baseTo != 10 && baseTo != 16) throw new NumberFormatException("Base out of Range");
        } catch (NumberFormatException e) {
            System.err.println("Invalid base to convert to: " + args[2]);
            System.exit(3);
        }
        
        try {
            number = Integer.parseInt(args[0], baseFrom);
        } catch (NumberFormatException e) {
            System.err.println("Invalid number to convert: " + args[0]);
            System.exit(4);
        }
        
        String strNumOut = "";
        switch (baseTo) {
            case 2:
                String temp = String.format("%X", number);
                for (int i=0; i<temp.length(); i++) strNumOut += map.get(temp.charAt(i));
                break;
            case 8:
                strNumOut = String.format("%o", number);
                break;
            case 10:
                strNumOut = String.format("%d", number);
                break;
            case 16:
                strNumOut = String.format("%X", number);
                break;
        }
        
        System.out.printf("%s in base %d is %s in base %d\n", args[0], baseFrom, strNumOut, baseTo);
    }
}