/** This class provides a method to evaluate fully parenthesized mathematical
 *  expressions.
 *
 *  @author Adam Blank
 */
public class Evaluator {
    /** Evaluates fully parenthesized mathematical expressions that use addition
     *  and multiplication. */
    public static int evaluate(String exp) throws NotImplementedException {
        if(EvaluatorUtilities.isNumber(exp)) {
            return Integer.parseInt(exp);
        }
        
        exp = exp.substring(1,  exp.length() - 1);
        
        char op = EvaluatorUtilities.nextOperator(exp);
        int opIndex = EvaluatorUtilities.nextOperatorIndex(exp);
        
        String left = exp.substring(0, opIndex);
        String right = exp.substring(opIndex + 1);
        
        // Find answer for left, find answer for right, op them together
        if (op == '+') {
            return evaluate(left) + evaluate(right);
        }
        else if (op == '*') {
            return evaluate(left) * evaluate(right);
        }
        else {
            throw new NotImplementedException();
        }
    }

    public static void main(String[] args) throws NotImplementedException {
        String[] exps = {"(1+(2*4))", "((1+1)*(2*(3+3)))"};
        for (int i = 0; i < exps.length; i++) {
            System.out.println(exps[i] + " = " + evaluate(exps[i].replaceAll(" ", "")));
        }
    }
}