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/*******************************************************************************
 * Copyright (c) 2006, 2014 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 v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * 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;
	}
}