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 2011-1-19)
   */
  package com.alibaba.cobar.parser.ast.expression.primary;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import com.alibaba.cobar.parser.ast.expression.Expression;
  import com.alibaba.cobar.parser.util.Pair;
  import com.alibaba.cobar.parser.visitor.SQLASTVisitor;
  
  /**
   * <code>'CASE' value? ('WHEN' condition 'THEN' result)+ ('ELSE' result)? 'END' </code>
   * 
   * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
   */
  public class CaseWhenOperatorExpression extends PrimaryExpression {
      private final Expression comparee;
      private final List<Pair<Expression, Expression>> whenList;
      private final Expression elseResult;
  
      /**
       * @param whenList never null or empry; no pair contains null key or value
       * @param comparee null for format of <code>CASE WHEN ...</code>, otherwise,
       *            <code>CASE comparee WHEN ...</code>
       */
      public CaseWhenOperatorExpression(Expression comparee, List<Pair<Expression, Expression>> whenList,
                                        Expression elseResult) {
          super();
          this.comparee = comparee;
          if (whenList instanceof ArrayList) {
              this.whenList = whenList;
          } else {
              this.whenList = new ArrayList<Pair<Expression, Expression>>(whenList);
          }
          this.elseResult = elseResult;
      }
  
      public Expression getComparee() {
          return comparee;
      }
  
      /**
       * @return never null or empty; no pair contains null key or value
       */
      public List<Pair<Expression, Expression>> getWhenList() {
          return whenList;
      }
  
      public Expression getElseResult() {
          return elseResult;
      }
  
      @Override
      public void accept(SQLASTVisitor visitor) {
          visitor.visit(this);
      }
  }
  