/*
 * Copyright (c) 2006, 2020 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;

import org.eclipse.persistence.jpa.jpql.WordParser;
import static org.eclipse.persistence.jpa.jpql.parser.Expression.*;

/**
 * This {@link IsExpressionFactory} creates a new expression when the portion of the query to parse
 * starts with <b>IS</b>.
 *
 * @see EmptyCollectionComparisonExpression
 * @see NullComparisonExpression
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public final class IsExpressionFactory extends ExpressionFactory {

    /**
     * The unique identifier of this {@link IsExpressionFactory}.
     */
    public static final String ID = IS;

    /**
     * Creates a new <code>IsExpressionFactory</code>.
     */
    public IsExpressionFactory() {
        super(ID, IS,
              IS_EMPTY,
              IS_NOT_EMPTY,
              IS_NOT_NULL,
              IS_NULL);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected AbstractExpression buildExpression(AbstractExpression parent,
                                                 WordParser wordParser,
                                                 String word,
                                                 JPQLQueryBNF queryBNF,
                                                 AbstractExpression expression,
                                                 boolean tolerant) {

        int position = wordParser.position();
        int index = position + 2;
        int count = wordParser.whitespaceCount(index);
        index += count;

        // IS NOT EMPTY or IS NOT NULL
        if (wordParser.startsWithIdentifier(NOT, index)) {
            index += 3;
            count = wordParser.whitespaceCount(index);
            index += count;

            // IS NOT EMPTY
            if (wordParser.startsWithIdentifier(EMPTY, index)) {
                expression = new EmptyCollectionComparisonExpression(parent, IS_NOT_EMPTY, expression);
            }
            // IS NOT NULL
            else if (wordParser.startsWithIdentifier(NULL, index)) {
                expression = new NullComparisonExpression(parent, IS_NOT_NULL, expression);
            }
            // IS NOT
            else {
                word = wordParser.substring(position, index - count);
                expression = new UnknownExpression(parent, word);
            }
        }
        // IS EMPTY
        else if (wordParser.startsWithIdentifier(EMPTY, index)) {
            expression = new EmptyCollectionComparisonExpression(parent, IS_EMPTY, expression);
        }
        // IS NULL
        else if (wordParser.startsWithIdentifier(NULL, index)) {
            expression = new NullComparisonExpression(parent, IS_NULL, expression);
        }
        // IS
        else {
            word = wordParser.substring(position, index - count);
            expression = new UnknownExpression(parent, word);
        }

        expression.parse(wordParser, tolerant);
        return expression;
    }
}