EDIT

// $Id$

/**

* Copyright (C) 2007 EDIT

* European Distributed Institute of Taxonomy 

* http://www.e-taxonomy.eu

* 

* The contents of this file are subject to the Mozilla Public License Version 1.1

* See LICENSE.TXT at the top of this package for the full license terms.

*/

package eu.etaxonomy.cdm.database.update.v25_30;

import java.sql.DatabaseMetaData;

import java.sql.ResultSet;

import java.sql.SQLException;

import org.apache.log4j.Logger;

import com.mysql.jdbc.exceptions.MySQLSyntaxErrorException;

import eu.etaxonomy.cdm.common.monitor.IProgressMonitor;

import eu.etaxonomy.cdm.database.DatabaseTypeEnum;

import eu.etaxonomy.cdm.database.ICdmDataSource;

import eu.etaxonomy.cdm.database.update.SchemaUpdaterStepBase;

/**

 * Creates the table needed by the {@link org.hibernate.id.enhanced.TableGenerator}

 * We expect the generator to be configured with <code>prefer_entity_table_as_segment_value</code> 

 * set to <code>true</code> (the generator does not make lots of sense without this option)

 * 

 * We also create sequences for all tables that are not empty. Otherwise we would run into 

 * id conflicts, because the generator expects the database to be empty and creates sequences,

 * if they do not exist, as needed.

 * 

 * @author n.hoffmann

 * @created Oct 27, 2010

 * @version 1.0

 */

public class SequenceTableCreator extends SchemaUpdaterStepBase {

	@SuppressWarnings("unused")

	private static final Logger logger = Logger.getLogger(SequenceTableCreator.class);

	// TODO These values are configurable in the enhanced.TableGenerator

	// can we retrieve these values from the identity generator directly?

	private static final String TABLE_NAME = "hibernate_sequences";

	private static final String SEGMENT_COLUMN_NAME = "sequence_name";

	private static final String VALUE_COLUMN_NAME = "next_val";

	private static final int INCREMENT_SIZE = 10;

	/**

	 * @param stepName

	 */

	protected SequenceTableCreator(String stepName) {

		super(stepName);

	}

	public static SequenceTableCreator NewInstance(String stepName){

		return new SequenceTableCreator(stepName);

	}

	/* (non-Javadoc)

	 * @see eu.etaxonomy.cdm.database.update.SchemaUpdaterStepBase#invoke(eu.etaxonomy.cdm.database.ICdmDataSource, eu.etaxonomy.cdm.common.IProgressMonitor)

	 */

	@Override

	public Integer invoke(ICdmDataSource datasource, IProgressMonitor monitor){

		boolean result = true;

		try {

			createSequenceTable(datasource, monitor);

			makeEntriesForEntityTables(datasource, monitor);

		} catch (SQLException e) {

			monitor.warning(e.getMessage(), e);

			result = false;

		}

		return (result == true ) ? 0 : null;

	}

	/**

	 * @param monitor 

	 * @param datasource 

	 * @return

	 * @throws SQLException 

	 */

	private boolean createSequenceTable(ICdmDataSource datasource, IProgressMonitor monitor) throws SQLException {

		boolean result = true;

		String createTableQuery = null;

		// TODO add create table statements for other supported databases

		if(datasource.getDatabaseType().equals(DatabaseTypeEnum.MySQL)){

			createTableQuery = "CREATE TABLE `" + TABLE_NAME + "` (" +

				"  `" + SEGMENT_COLUMN_NAME + "` varchar(255) NOT NULL," +

				"  `" + VALUE_COLUMN_NAME + "` bigint(20) default NULL," +

				"  PRIMARY KEY  (`" + SEGMENT_COLUMN_NAME + "`)" +

				");";

		}else{

			throw new RuntimeException("Database type " + datasource.getDatabaseType() + " is currently not supported by the updater");

		}

		datasource.executeUpdate(createTableQuery);

		return result;

	}

	/**

	 * @param monitor 

	 * @param datasource 

	 * @return

	 * @throws SQLException 

	 */

	private void makeEntriesForEntityTables(ICdmDataSource datasource, IProgressMonitor monitor) throws SQLException {

		DatabaseMetaData metaData = datasource.getMetaData();

		ResultSet resultSet = metaData.getTables(datasource.getDatabase(), null, null, null);

		String maxIdQuery = "SELECT MAX(ID) FROM @tableName";

		String insertQuery = "INSERT INTO " + TABLE_NAME + " ( " + SEGMENT_COLUMN_NAME + ", " + VALUE_COLUMN_NAME + ")" +

				" VALUES ('@tableName', (@maxId + " + INCREMENT_SIZE + "))";

		Object maxId = null;

		while(resultSet.next()){

			// through debugging we found out that the table name is in column 3. 

			// TODO improve this if you know that this will not always be the case for all database types 

			// and/or if you know of a good way to do it in more generic way

			String tableName = resultSet.getString(3);

			// this way we simply filter out all relation tables, could have done this with a tableNamePattern passed to getTables(...)

			// but this was faster. 

			if(tableName.contains("_")){

				continue;

			}

			try{

				String query = maxIdQuery.replace("@tableName", tableName);

				maxId = datasource.getSingleValue(query);

			}catch(MySQLSyntaxErrorException e){

				// table does not have a column id, so it is not an entity table

				maxId = null;

			}

			// empty tables will not set the maxId. 

			// Empty tables will also not need to be updated, because the identity generator creates sequences for tables it did not have before

			if(maxId != null){

				monitor.subTask("Inserting sequence for table: " + tableName + " with maxId: " + maxId);

				String query = insertQuery.replace("@tableName", tableName);

				query = query.replace("@maxId", maxId.toString());

				datasource.executeUpdate(query);

			}

		}

	}

}