import java.util.*;

public class roman_calculator {

    Scanner scan = new Scanner(System.in);

    boolean doCalculation()
    {
        char operator;
        int operand1, operand2, answer;
        operator = getOperator();
        if (operator == 'q')
            return false;
        do {
        operand1 = getOperand(1);
        } while (operand1 == -1);

        do {
        operand2 = getOperand(2);
        } while (operand2 == -1);
        //System.out.println(operand1 + operator + operand2);

        answer = doArtithmetic(operand1, operand2, operator);

        System.out.print("Answer= " + convert_to_Roman(answer, operator));

        return true;
    }

    char getOperator()
    {
        char operator = 'q';
        //user operator
        boolean operator_is_good=false;

        do {
            System.out.print("Enter an Operator: + - * / q for quit: ");
            String strOperator = scan.nextLine();
            strOperator = strOperator.trim();
            if (strOperator.length() == 0)
                continue;
            operator = strOperator.charAt(0);
            operator_is_good=false;

            switch (operator) {
            case 'q':
            case '+':
            case '-':
            case '*':
            case '/':
                operator_is_good = true;
                break;
            default:
                System.out.println("Your operator is bad ... try again:");
                break;
            }
        } while (!operator_is_good);
        return operator;
    }
    // This routine prompts the user for either operand1 or operand2
    // depending on the value of which.  This routine uppercases the
    // input and calls convert_from_Roman to create an integer.
    // If the input is invalid ( negative return from convert_from_Roman)
    // then complain and prompt the user again.
    int getOperand(int which)
    {
        System.out.print("Enter Operand "+which + ":");

        String input;


        input = scan.nextLine();
        input = input.toUpperCase();
        int value = convert_from_Roman(input);

        return value;

    }

    // Routine to convert an integer to a Roman Numeral String.
    // When you do this routine, you might find it handy to
    // create a utility routine that looks like:
    //  String addRomanDigit(String starting, int num, char digit)
    String convert_to_Roman(int value, char operator)
    {
        String roman ="";

        while (value != 0) {
            if (value >= 1000) {
                roman = roman + 'M';
                value = value - 1000;
            }
            else if (value >= 500) {
                roman = roman + 'D';
                value = value - 500;
            }
            else if (value >= 100) {
                roman = roman + 'C';
                value = value - 100;
            }
            else if (value >= 50) {
                roman = roman + 'L';
                value = value - 50;
            }
            else if (value >= 10) {
                roman = roman + 'X';
                value = value - 10;
            }
            else if (value >=5) {
                roman = roman + 'V';
                value = value - 5;
            }
            else if (value >= 1) {
                roman = roman + 'I';
                value = value - 1;
            }
        }

        return roman;

    }

    // Convert Roman Numeral String to an integer.  If the
    // Roman Numeral String is invalid, return -1
    int convert_from_Roman(String value)
    {
        int numValue = 0;
        value = value.trim(); //value = IV
        int len = value.length(); //len = 2

        for (int i=0; i<len; i++)
        {
            char location = value.charAt(i);
            //System.out.println(value.charAt(i));
            if (location == 'I')
                numValue = numValue + 1;
            else if (location == 'V')
                numValue = numValue + 5;
            else if (location == 'X')
                numValue = numValue + 10;
            else if (location == 'L')
                numValue = numValue + 50;
            else if (location == 'C')
                numValue = numValue + 100;
            else if (location == 'D')
                numValue = numValue + 500;
            else if (location == 'M')
                numValue = numValue + 1000;
            else {
                numValue = -1;
                System.out.println(value + " has a bad character at position: " + i);
                return numValue;

            }

        }
        //System.out.println(numValue);

        return numValue;

    }

    int doArtithmetic(int operand1, int operand2, char operator)
    {
        int answer = 0;
        //logic to compute answer
        switch (operator) {
        case '+':
            answer = operand1 + operand2;
            break;
        case '-':
            answer = operand1 - operand2;
            break;
        case '/':
            answer = operand1 / operand2;
            break;
        case '*':
            answer = operand1 * operand2;
            break;

        }

        return answer;
    }

    public static void main(String[] args) {
        roman_calculator rc = new roman_calculator();
        while (rc.doCalculation())
        {
            System.out.println();
        }
        System.out.println("Finished Roman Computations");

    }
}