content: /*
   * Copyright 1999-2012 Alibaba Group.
   *  
   * 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.
   */
  /**
   * (created at 2011-1-25)
   */
  package com.alibaba.cobar.parser.ast.fragment;
  
  import java.util.ArrayList;
  import java.util.LinkedList;
  import java.util.List;
  
  import com.alibaba.cobar.parser.ast.ASTNode;
  import com.alibaba.cobar.parser.ast.expression.Expression;
  import com.alibaba.cobar.parser.util.Pair;
  import com.alibaba.cobar.parser.visitor.SQLASTVisitor;
  
  /**
   * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
   */
  public class OrderBy implements ASTNode {
      /** might be {@link LinkedList} */
      private final List<Pair<Expression, SortOrder>> orderByList;
  
      public List<Pair<Expression, SortOrder>> getOrderByList() {
          return orderByList;
      }
  
      /**
       * performance tip: linked list is used
       */
      public OrderBy() {
          this.orderByList = new LinkedList<Pair<Expression, SortOrder>>();
      }
  
      /**
       * performance tip: expect to have only 1 order item
       */
      public OrderBy(Expression expr, SortOrder order) {
          this.orderByList = new ArrayList<Pair<Expression, SortOrder>>(1);
          this.orderByList.add(new Pair<Expression, SortOrder>(expr, order));
      }
  
      public OrderBy(List<Pair<Expression, SortOrder>> orderByList) {
          if (orderByList == null)
              throw new IllegalArgumentException("order list is null");
          this.orderByList = orderByList;
      }
  
      public OrderBy addOrderByItem(Expression expr, SortOrder order) {
          orderByList.add(new Pair<Expression, SortOrder>(expr, order));
          return this;
      }
  
      @Override
      public void accept(SQLASTVisitor visitor) {
          visitor.visit(this);
      }
  }
  