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.comparison;
  
  import java.util.Map;
  
  import com.alibaba.cobar.parser.ast.expression.AbstractExpression;
  import com.alibaba.cobar.parser.ast.expression.Expression;
  import com.alibaba.cobar.parser.ast.expression.ReplacableExpression;
  import com.alibaba.cobar.parser.visitor.SQLASTVisitor;
  
  /**
   * @author <a href="mailto:shuo.qius@alibaba-inc.com">QIU Shuo</a>
   */
  public class ComparisionIsExpression extends AbstractExpression implements ReplacableExpression {
      public static final int IS_NULL = 1;
      public static final int IS_TRUE = 2;
      public static final int IS_FALSE = 3;
      public static final int IS_UNKNOWN = 4;
      public static final int IS_NOT_NULL = 5;
      public static final int IS_NOT_TRUE = 6;
      public static final int IS_NOT_FALSE = 7;
      public static final int IS_NOT_UNKNOWN = 8;
  
      private final int mode;
      private final Expression operand;
  
      /**
       * @param mode {@link #IS_NULL} or {@link #IS_TRUE} or {@link #IS_FALSE} or
       *            {@link #IS_UNKNOWN} or {@link #IS_NOT_NULL} or
       *            {@link #IS_NOT_TRUE} or {@link #IS_NOT_FALSE} or
       *            {@link #IS_NOT_UNKNOWN}
       */
      public ComparisionIsExpression(Expression operand, int mode) {
          this.operand = operand;
          this.mode = mode;
      }
  
      public int getMode() {
          return mode;
      }
  
      public Expression getOperand() {
          return operand;
      }
  
      @Override
      public int getPrecedence() {
          return PRECEDENCE_COMPARISION;
      }
  
      @Override
      public Object evaluationInternal(Map<? extends Object, ? extends Object> parameters) {
          return UNEVALUATABLE;
      }
  
      private Expression replaceExpr;
  
      @Override
      public void setReplaceExpr(Expression replaceExpr) {
          this.replaceExpr = replaceExpr;
      }
  
      @Override
      public void clearReplaceExpr() {
          this.replaceExpr = null;
      }
  
      @Override
      public void accept(SQLASTVisitor visitor) {
          if (replaceExpr == null)
              visitor.visit(this);
          else
              replaceExpr.accept(visitor);
      }
  }
  