/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2005-2008, Open Source Geospatial Foundation (OSGeo)
 * 
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 */
package org.geotools.referencing.factory.epsg;

// J2SE dependencies
import java.sql.Statement;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

// Geotools dependencies
import org.geotools.factory.Hints;


/**
 * Adapts SQL statements for HSQL. The HSQL database engine doesn't understand
 * the parenthesis in (INNER JOIN ... ON) statements for the "BursaWolfParameters"
 * query. Unfortunately, those parenthesis are required by MS-Access. We need to
 * removes them programmatically here.
 *
 * @since 2.2
 * @source $URL$
 * @version $Id$
 * @author Martin Desruisseaux
 */
final class HsqlDialectEpsgFactory extends AnsiDialectEpsgFactory {
    /**
     * The regular expression pattern for searching the "FROM (" clause.
     * This is the pattern for the opening parenthesis.
     */
    private static final Pattern OPENING_PATTERN =
            Pattern.compile("\\s+FROM\\s*\\(",
            Pattern.CASE_INSENSITIVE);

    /**
     * Constructs the factory for the given connection to the HSQL database.
     * @throws SQLException 
     */
    public HsqlDialectEpsgFactory(final Hints hints) throws SQLException {
        super(hints, HsqlEpsgDatabase.createDataSource());
    }
    
    /**
     * Constructs the factory for the given connection to the HSQL database.
     */
    public HsqlDialectEpsgFactory(final Hints hints, final javax.sql.DataSource dataSource) {
        super(hints, dataSource);
    }

    /**
     * If the query contains a "FROM (" expression, remove the parenthesis.
     */
    public String adaptSQL(String query) {
        query = super.adaptSQL(query);
        final Matcher matcher = OPENING_PATTERN.matcher(query);
        if (matcher.find()) {
            final int opening = matcher.end()-1;
            final int length  = query.length();
            int closing = opening;
            for (int count=0; ; closing++) {
                if (closing >= length) {
                    // Should never happen with well formed SQL statement.
                    // If it happen anyway, don't change anything and let
                    // the HSQL driver produces a "syntax error" message.
                    return query;
                }
                switch (query.charAt(closing)) {
                    case '(': count++; break;
                    case ')': count--; break;
                    default : continue;
                }
                if (count == 0) {
                    break;
                }
            }
            query = query.substring(0,         opening) +
                    query.substring(opening+1, closing) +
                    query.substring(closing+1);
        }
        return query;
    }

    /**
     * Shutdown the HSQL database engine. This method is invoked automatically at JVM
     * shutdown time just before to close the connection.
     */
    protected void shutdown(final boolean active) throws SQLException {
        if (active) {
            final Statement statement = getConnection().createStatement();
            statement.execute("SHUTDOWN");
            statement.close();
        }
        super.shutdown(active);
    }
}