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package com.salesforce.phoenix.filter;

import java.util.Iterator;

import com.salesforce.phoenix.expression.ArrayConstructorExpression;
import com.salesforce.phoenix.expression.CaseExpression;
import com.salesforce.phoenix.expression.Expression;
import com.salesforce.phoenix.expression.IsNullExpression;
import com.salesforce.phoenix.expression.RowKeyColumnExpression;
import com.salesforce.phoenix.expression.RowValueConstructorExpression;
import com.salesforce.phoenix.expression.visitor.TraverseAllExpressionVisitor;


/**
 * 
 * Implementation of ExpressionVisitor for the expression used by the
 * BooleanExpressionFilter that looks for expressions that need to be
 * evaluated upon completion. Examples include:
 * - CaseExpression with an else clause, since upon completion, the
 * else clause would apply if the when clauses could not be evaluated
 * due to the absense of a value.
 * - IsNullExpression that's not negated, since upon completion, we
 * know definitively that a column value was not found.
 * - row key columns are used, since we may never have encountered a
 * key value column of interest, but the expression may evaluate to true
 * just based on the row key columns.
 * @author jtaylor
 * @since 0.1
 */
public class EvaluateOnCompletionVisitor extends TraverseAllExpressionVisitor<Void> {
    private boolean evaluateOnCompletion = false;
    
    public boolean evaluateOnCompletion() {
        return evaluateOnCompletion;
    }
    
    @Override
    public Iterator<Expression> visitEnter(IsNullExpression node) {
        evaluateOnCompletion |= !node.isNegate();
        return null;
    }
    @Override
    public Iterator<Expression> visitEnter(CaseExpression node) {
        evaluateOnCompletion |= node.hasElse();
        return null;
    }
    @Override
    public Void visit(RowKeyColumnExpression node) {
        evaluateOnCompletion = true;
        return null;
    }
    @Override
    public Iterator<Expression> visitEnter(RowValueConstructorExpression node) {
        evaluateOnCompletion = true;
        return null;
    }
    
    @Override
    public Iterator<Expression> visitEnter(ArrayConstructorExpression node) {
        evaluateOnCompletion = true;
        return null;
    }

}
