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  package org.apache.cayenne.exp.parser;
  
  import java.util.function.Function;
  
  import org.apache.cayenne.exp.Expression;
  import org.apache.cayenne.exp.ExpressionException;
  import org.apache.cayenne.exp.ExpressionFactory;
  
  /**
   * Superclass of aggregated conditional nodes such as NOT, AND, OR. Performs
   * extra checks on parent and child expressions to validate conditions that are
   * not addressed in the Cayenne expressions grammar.
   * 
   * @since 1.1
   */
  public abstract class AggregateConditionNode extends SimpleNode {
  
  	private static final long serialVersionUID = -636699350691988809L;
  
  	AggregateConditionNode(int i) {
  		super(i);
  	}
  
  	@Override
  	protected boolean pruneNodeForPrunedChild(Object prunedChild) {
  		return false;
  	}
  
  	@Override
  	protected Object transformExpression(Function<Object, Object> transformer) {
  		Object transformed = super.transformExpression(transformer);
  
  		if (!(transformed instanceof AggregateConditionNode)) {
  			return transformed;
  		}
  
  		AggregateConditionNode condition = (AggregateConditionNode) transformed;
  
  		// prune itself if the transformation resulted in
  		// no children or a single child
  		switch (condition.getOperandCount()) {
  		case 1:
  			if (condition instanceof ASTNot || condition instanceof ASTWhen) {
  				return condition;
  			} else {
  				return condition.getOperand(0);
  			}
  		case 0:
  			return PRUNED_NODE;
  		default:
  			return condition;
  		}
  	}
  
  	@Override
  	protected boolean isValidParent(Node n) {
  		return n instanceof AggregateConditionNode
  				|| n instanceof ASTExists
  				|| n instanceof ASTNotExists;
  	}
  
  	@Override
  	public void jjtAddChild(Node n, int i) {
  		// this is a check that we can't handle properly
  		// in the grammar... do it here...
  
  		// only allow conditional nodes...no scalars
  		if (!(n instanceof ConditionNode) && !(n instanceof AggregateConditionNode)) {
  			String label = (n instanceof SimpleNode) ? ((SimpleNode) n).expName() : String.valueOf(n);
  			throw new ExpressionException(expName() + ": invalid child - " + label);
  		}
  
  		super.jjtAddChild(n, i);
  	}
  
  	/**
  	 * @inheritDoc
  	 * @since 5.0
  	 */
  	@Override
  	public Expression exists() {
  		return ExpressionFactory.exists(this);
  	}
  
  	/**
  	 * @inheritDoc
  	 * @since 5.0
  	 */
  	@Override
  	public Expression notExists() {
  		return ExpressionFactory.notExists(this);
  	}
  }
  