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package org.apache.cayenne.exp.parser;

import org.apache.commons.collections.Transformer;
import org.apache.cayenne.exp.ExpressionException;

/**
 * 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
 * @author Andrei Adamchik
 */
public abstract class AggregateConditionNode extends SimpleNode {
    AggregateConditionNode(int i) {
        super(i);
    }

    protected boolean pruneNodeForPrunedChild(Object prunedChild) {
        return false;
    }

    protected Object transformExpression(Transformer 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 :
                return condition.getOperand(0);
            case 0 :
                return PRUNED_NODE;
            default :
                return condition;
        }
    }

    public void jjtSetParent(Node n) {
        // this is a check that we can't handle properly
        // in the grammar... do it here...

        // disallow non-aggregated condition parents...
        if (!(n instanceof AggregateConditionNode)) {
            String label =
                (n instanceof SimpleNode)
                    ? ((SimpleNode) n).expName()
                    : String.valueOf(n);
            throw new ExpressionException(expName() + ": invalid parent - " + label);
        }

        super.jjtSetParent(n);
    }

    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);
    }
}