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  package org.apache.cayenne.exp.parser;
  
  import org.apache.cayenne.exp.Expression;
  import org.apache.cayenne.util.ConversionUtil;
  
  import java.io.IOException;
  import java.util.List;
  
  /**
   * "CASE-WHEN" expression root node.
   *
   * @see org.apache.cayenne.exp.ExpressionFactory#caseWhen(List, List, Expression)
   * @since 5.0
   */
  public class ASTCaseWhen extends SimpleNode {
  
      private boolean hasDefault;
  
      public ASTCaseWhen(boolean hasDefault, Expression... nodes) {
          super(0);
          for (int i = 0; i < nodes.length; i++) {
              jjtAddChild((Node) nodes[i], i);
          }
          connectChildren();
          this.hasDefault = hasDefault;
      }
  
      public ASTCaseWhen(int id) {
          super(id);
      }
  
      /**
       * Creates a copy of this expression node, without copying children.
       */
      @Override
      public Expression shallowCopy() {
          return new ASTCaseWhen(id);
      }
  
      @Override
      protected String getExpressionOperator(int index) {
          return "case";
      }
  
      @Override
      protected Object evaluateNode(Object o) throws Exception {
          int numChildren = jjtGetNumChildren();
          if (numChildren == 0) {
              return null;
          }
          for (int i = 0; i < numChildren - 1; i = i + 2) {
              Object evaluatedWhen = evaluateChild(i, o);
              if (ConversionUtil.toBoolean(evaluatedWhen)) {
                  return evaluateChild(i + 1, o);
              }
          }
          if (hasDefault) {
              return evaluateChild(numChildren - 1, o);
          }
          return null;
      }
  
      @Override
      public int getType() {
          return Expression.CASE_WHEN;
      }
  
      @Override
      public void appendAsEJBQL(List<Object> parameterAccumulator, Appendable out, String rootId) throws IOException {
          throw new UnsupportedOperationException("EJBQL 'case when' is not supported");
      }
  }
  