/*
 * JEF - Copyright 2009-2010 Jiyi (mr.jiyi@gmail.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package jef.database.jsqlparser.expression;

import java.math.BigDecimal;

import jef.database.jsqlparser.visitor.Expression;
import jef.database.jsqlparser.visitor.ExpressionType;
import jef.database.jsqlparser.visitor.ExpressionVisitor;
import jef.database.jsqlparser.visitor.SqlValue;

/**
 * It represents a "-" before an expression
 */
public class InverseExpression implements Expression, SqlValue {

	private Expression expression;

	public InverseExpression() {
	}

	public InverseExpression(Expression expression) {
		setExpression(expression);
	}

	public Expression getExpression() {
		return expression;
	}

	public void setExpression(Expression expression) {
		this.expression = expression;
	}

	public void accept(ExpressionVisitor expressionVisitor) {
		expressionVisitor.visit(this);
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		appendTo(sb);
		return sb.toString();
	}

	/**
	 * 取相反的值
	 * 
	 * @param ex
	 * @return
	 */
	public static Expression getInverse(Expression ex) {
		if (ex instanceof InverseExpression) {
			return ((InverseExpression) ex).getExpression();
		} else {
			if (ex instanceof BinaryExpression) {
				ex = new Parenthesis(ex);
			}
			return new InverseExpression(ex);
		}
	}

	public void appendTo(StringBuilder sb) {
		expression.appendTo(sb.append('-'));
	}

	public ExpressionType getType() {
		if (expression == null) {
			return ExpressionType.arithmetic;
		}
		return expression.getType();
	}

	public Object getValue() {
		if (expression instanceof SqlValue) {
			SqlValue sv = (SqlValue) expression;
			Object obj = sv.getValue();
			if (obj == null)
				return obj;

			BigDecimal num;
			if ((obj instanceof BigDecimal)) {
				num = (BigDecimal) obj;
			} else {
				num = new BigDecimal(String.valueOf(obj));
			}
			return sv.formatNumber(num.negate());
		}
		return null;
	}

	public Object formatNumber(BigDecimal negate) {
		return ((SqlValue)expression).formatNumber(negate);
	}
}