/*!
* Copyright 2010 - 2013 Pentaho Corporation.  All rights reserved.
*
* 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 org.apache.hadoop.hive.ql.parse;


/**
 * Library of utility functions used in the parse code.
 *
 */
public final class ParseUtils {

  /**
   * Tests whether the parse tree node is a join token.
   *
   * @param node
   *          The parse tree node
   * @return boolean
   */
  public static boolean isJoinToken(ASTNode node) {
    switch (node.getToken().getType()) {
    case HiveParser.TOK_JOIN:
    case HiveParser.TOK_LEFTOUTERJOIN:
    case HiveParser.TOK_RIGHTOUTERJOIN:
    case HiveParser.TOK_FULLOUTERJOIN:
      return true;
    default:
      return false;
    }
  }

  /**
   * Performs a descent of the leftmost branch of a tree, stopping when either a
   * node with a non-null token is found or the leaf level is encountered.
   *
   * @param tree
   *          candidate node from which to start searching
   *
   * @return node at which descent stopped
   */
  public static ASTNode findRootNonNullToken(ASTNode tree) {
    while ((tree.getToken() == null) && (tree.getChildCount() > 0)) {
      tree = (ASTNode) tree.getChild(0);
    }
    return tree;
  }

  private ParseUtils() {
    // prevent instantiation
  }
}