/* Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.qpid.filter;

/**
 * An expression which performs an operation on two expression values.
 */
public abstract class BinaryExpression implements Expression
{
    protected Expression left;
    protected Expression right;

    public BinaryExpression(Expression left, Expression right)
    {
        this.left = left;
        this.right = right;
    }

    public Expression getLeft()
    {
        return left;
    }

    public Expression getRight()
    {
        return right;
    }

    /**
     * @see Object#toString()
     */
    public String toString()
    {
        return "(" + left.toString() + " " + getExpressionSymbol() + " " + right.toString() + ")";
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see Object#hashCode()
     */
    public int hashCode()
    {
        return toString().hashCode();
    }

    /**
     * TODO: more efficient hashCode()
     *
     * @see Object#equals(Object)
     */
    public boolean equals(Object o)
    {

        if ((o == null) || !this.getClass().equals(o.getClass()))
        {
            return false;
        }

        return toString().equals(o.toString());

    }

    /**
     * Returns the symbol that represents this binary expression.  For example, addition is
     * represented by "+"
     *
     * @return
     */
    public abstract String getExpressionSymbol();

    /**
     * @param expression
     */
    public void setRight(Expression expression)
    {
        right = expression;
    }

    /**
     * @param expression
     */
    public void setLeft(Expression expression)
    {
        left = expression;
    }

}
