/*******************************************************************************
 * Copyright (c) 2006, 2013 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;

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

/**
 * This {@link ComparisonExpressionFactory} creates a new {@link ComparisonExpression} when the
 * portion of the query to parse starts with <b>&lt;</b>, <b>&gt;</b>, <b>{@literal <>}</b>, <b>&lt;=</b>,
 * <b>&gt;=</b> or <b>=</b>.
 *
 * @see ComparisonExpression
 *
 * @version 2.4
 * @since 2.3
 * @author Pascal Filion
 */
@SuppressWarnings("nls")
public final class ComparisonExpressionFactory extends ExpressionFactory {

	/**
	 * The unique identifier of this {@link ComparisonExpressionFactory}.
	 */
	public static final String ID = "comparison";

	/**
	 * Creates a new <code>ComparisonExpressionFactory</code>.
	 */
	public ComparisonExpressionFactory() {
		super(ID, DIFFERENT,
		          EQUAL,
		          GREATER_THAN,
		          GREATER_THAN_OR_EQUAL,
		          LOWER_THAN,
		          LOWER_THAN_OR_EQUAL);
	}

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

		String operator = null;

		// First look for known operator (<, <=, =, =>, <>)
		switch (wordParser.character()) {

			// <, <=, <>
			case '<': {
				switch (wordParser.character(wordParser.position() + 1)) {
					case '=': {
						operator = LOWER_THAN_OR_EQUAL;
						break;
					}
					case '>': {
						operator = DIFFERENT;
						break;
					}
					default: {
						operator = LOWER_THAN;
						break;
					}
				}
				break;
			}

			// >, >=
			case '>': {
				switch (wordParser.character(wordParser.position() + 1)) {
					case '=': {
						operator = GREATER_THAN_OR_EQUAL;
						break;
					}
					default: {
						operator = GREATER_THAN;
						break;
					}
				}
				break;
			}

			// =
			case '=': {
				operator = EQUAL;
				break;
			}
		}

		// Now look for additional identifiers
		if (operator == null) {
			for (String identifier : identifiers()) {
				if (wordParser.startsWith(identifier)) {
					operator = identifier;
					break;
				}
			}
		}

		// The operator was found, create the expression
		if (operator != null) {

			ComparisonExpression comparisonExpression = new ComparisonExpression(parent, operator);
			comparisonExpression.parse(wordParser, tolerant);

			if (expression != null) {
				comparisonExpression.setLeftExpression(expression);
			}

			return comparisonExpression;
		}

		return null;
	}
}