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/*
 * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation
//
package org.eclipse.persistence.jpa.jpql.parser;

/**
 * The second and third arguments of the SUBSTRING function denote the starting position and
 * length of the substring to be returned. These arguments are integers. The first position of a
 * string is denoted by 1. The SUBSTRING function returns a string.
 * 
 * JPA 1.0:
 * 
BNF ::= SUBSTRING(string_primary, simple_arithmetic_expression, simple_arithmetic_expression)
 * 
 * JPA 2.0:
 * 
BNF ::= SUBSTRING(string_primary, simple_arithmetic_expression [, simple_arithmetic_expression])
 * 
 * JPA 2.1:
 * 
BNF ::= SUBSTRING(string_expression, arithmetic_expression [, arithmetic_expression])
 *
 * Example: UPDATE Employee e SET e.firstName = SUBSTRING('TopLink Workbench', 1, 8)
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public final class SubstringExpression extends AbstractTripleEncapsulatedExpression {

    /**
     * Creates a new SubstringExpression.
     *
     * @param parent The parent of this expression
     */
    public SubstringExpression(AbstractExpression parent) {
        super(parent, SUBSTRING);
    }

    /**
     * {@inheritDoc}
     */
    public void accept(ExpressionVisitor visitor) {
        visitor.visit(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getParameterQueryBNFId(int index) {
        switch (index) {
            case 0:  return InternalSubstringStringExpressionBNF.ID;
            default: return InternalSubstringPositionExpressionBNF.ID;
        }
    }

    /**
     * {@inheritDoc}
     */
    public JPQLQueryBNF getQueryBNF() {
        return getQueryBNF(FunctionsReturningStringsBNF.ID);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected boolean isThirdExpressionOptional() {
        return true;
    }
}