package expression;

import java.math.BigDecimal;
import java.math.BigInteger;

/**
 * @author Doschennikov Nikita (me@fymio.us)
 */
public class Log extends AbstractBinaryOperation {
    public Log(AbstractExpression l, AbstractExpression r) { super(l, r); }

    @Override protected String  getOperator()  { return "//"; }
    @Override protected int     getPriority()  { return 3; }
    @Override protected boolean isRightAssoc() { return true; }

    @Override
    protected int applyInt(int a, int b) {
        if (a <= 0) throw new ArithmeticException("logarithm of non-positive number");
        if (b <= 1) throw new ArithmeticException("logarithm base must be > 1");
        int result = 0;
        int power = 1;
        while (power <= a / b) {
            power *= b;
            result++;
        }
        return result;
    }

    @Override
    protected BigInteger applyBi(BigInteger a, BigInteger b) {
        if (a.signum() <= 0) throw new ArithmeticException("logarithm of non-positive number");
        if (b.compareTo(BigInteger.TWO) < 0) throw new ArithmeticException("logarithm base must be > 1");
        int result = 0;
        BigInteger power = BigInteger.ONE;
        while (power.multiply(b).compareTo(a) <= 0) {
            power = power.multiply(b);
            result++;
        }
        return BigInteger.valueOf(result);
    }

    @Override
    protected BigDecimal applyBd(BigDecimal a, BigDecimal b) {
        throw new UnsupportedOperationException("log not supported for BigDecimal");
    }
}