package bjc.dicelang;

/**
 * Implements a class for combining two dice with an operator
 * 
 * @author ben
 *
 */
public class OperatorDiceExpression implements IDiceExpression {
	/*
	 * The operator to use for combining the dice
	 */
	private DiceExpressionType	type;

	/*
	 * The dice on the left side of the expression
	 */
	private IDiceExpression		left;

	/*
	 * The dice on the right side of the expression
	 */
	private IDiceExpression		right;

	/**
	 * Create a new compound expression using the specified parameters
	 * 
	 * @param rght
	 *            The die on the right side of the expression
	 * @param lft
	 *            The die on the left side of the expression
	 * @param type
	 *            The operator to use for combining the dices
	 */
	public OperatorDiceExpression(IDiceExpression rght,
			IDiceExpression lft, DiceExpressionType type) {
		this.right = rght;
		this.left = lft;
		this.type = type;
	}

	@Override
	public int roll() {
		/*
		 * Handle each operator
		 */
		switch (type) {
			case ADD:
				return right.roll() + left.roll();
			case SUBTRACT:
				return right.roll() - left.roll();
			case MULTIPLY:
				return right.roll() * left.roll();
			case DIVIDE:
				/*
				 * Round to keep results as integers. We don't really have
				 * any need for floating-point dice, and continuous
				 * probability is a pain
				 */
				try {
					return right.roll() / left.roll();
				} catch (ArithmeticException aex) {
					UnsupportedOperationException usex = new UnsupportedOperationException(
							"Attempted to divide by zero."
									+ " Problematic expression is "
									+ left);

					usex.initCause(aex);

					throw usex;
				}
			default:
				throw new IllegalArgumentException(
						"Got passed a invalid ScalarExpressionType ("
								+ type + "). WAT");

		}
	}

	@Override
	public String toString() {
		return "dice-exp[type=" + type + ", l="
				+ left.toString() + ", r="
				+ right.toString() + "]";
	}
}