/**
 * 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.hadoop.hive.ql.lib;

import java.util.Stack;

import org.apache.hadoop.hive.ql.parse.SemanticException;

/**
 * Rule that matches a particular type of node.
 */
public class TypeRule implements Rule {

  private Class<?> nodeClass;

  public TypeRule(Class<?> nodeClass) {
    this.nodeClass = nodeClass;
  }

  @Override
  public int cost(Stack<Node> stack) throws SemanticException {
    if (stack == null) {
      return -1;
    }
    if (nodeClass.isInstance(stack.peek())) {
      return 1;
    }
    return -1;
  }

  @Override
  public String getName() {
    return nodeClass.getName();
  }
}