/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.id;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.dialect.DB2Dialect;
import org.hibernate.dialect.DerbyDialect;
import org.hibernate.dialect.Dialect;
import org.hibernate.dialect.HSQLDialect;
import org.hibernate.dialect.Oracle8iDialect;
import org.hibernate.dialect.SQLServer2012Dialect;
import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.exception.GenericJDBCException;
import org.hibernate.jdbc.Work;

/**
 * @author Andrea Boriero
 */
public class SequenceValueExtractor {

	private final Dialect dialect;
	private final String queryString;

	public SequenceValueExtractor(Dialect dialect, String sequenceName) {
		this.dialect = dialect;
		if ( dialect instanceof DerbyDialect ) {
			queryString = "VALUES SYSCS_UTIL.SYSCS_PEEK_AT_SEQUENCE('HIBERNATE_ORM_TEST', '" + sequenceName.toUpperCase() + "')";
		}
		else if ( dialect instanceof DB2Dialect ) {
			queryString = "values PREVIOUS value for " + sequenceName;
		}
		else if ( dialect instanceof Oracle8iDialect ) {
			queryString = "select " + sequenceName + ".currval from dual";
		}
		else if ( dialect instanceof SQLServer2012Dialect ) {
			queryString = "SELECT CONVERT(varchar(200), Current_value) FROM sys.sequences WHERE name = '" + sequenceName + "'";
		}
		else if ( dialect instanceof HSQLDialect ) {

			queryString = "call current value for " + sequenceName;
		}
		else {
			queryString = "select currval('" + sequenceName + "');";
		}
	}

	public long extractSequenceValue(final SessionImplementor sessionImpl) {
		class WorkImpl implements Work {
			private long value;

			public void execute(Connection connection) throws SQLException {
				Session session = (Session) sessionImpl;
				Transaction transaction = session.beginTransaction();
				try {
					final PreparedStatement query = sessionImpl.getJdbcCoordinator()
							.getStatementPreparer()
							.prepareStatement( queryString );
					ResultSet resultSet = sessionImpl.getJdbcCoordinator().getResultSetReturn().extract( query );
					resultSet.next();
					value = resultSet.getLong( 1 );

					resultSet.close();
					transaction.commit();
				}catch (GenericJDBCException e){
					transaction.rollback();
					throw e;
				}
				if ( dialect instanceof DerbyDialect ) {
					value--;
				}
			}
		}
		WorkImpl work = new WorkImpl();
		((Session) sessionImpl).doWork( work );
		return work.value;
	}
}