package com.sbs.wceeconvert.migrate;

import java.util.HashMap;
import java.util.Map;

import com.sbs.wceeconvert.Converter;
import com.sbs.wceeconvert.WCEEConvertVersion;

/**
 * The migration class contains information from converting
 * one <code>WCEEConvertVersion<code> to another, all the way up to
 * <code>WCEEConvertVersion.CURRENT_VERSION</code>.
 */
public final class Migration
{
	protected WCEEConvertVersion oldVersion;
	protected Map migrationPatterns;

	/**
	 * Formal constructor to initialize what version we are currently on
	 * so we know how to upgrade to <code>CURRENT_VERSION</code>.
	 * 
	 * @param oldVersion The version contained in the database.
	 */
	public Migration(WCEEConvertVersion oldVersion)
	{
		this.oldVersion = oldVersion;
		this.initVersionUpgrades();
	}

	/**
	 * Register the classes, versions, and upgrade advisors.
	 */
	private void initVersionUpgrades()
	{
		migrationPatterns = new HashMap();
		migrationPatterns.put("0.0.0", "com.sbs.wceeconvert.migrate.MigrationPattern_0_0_0");
		migrationPatterns.put("1.0.0", "com.sbs.wceeconvert.migrate.MigrationPattern_1_0_0");
	}

	/**
	 * Migrate the database versions.
	 * 
	 * @param converter The converter that is converting the database.
	 */
	public void migrate(Converter converter)
	throws MigrationException
	{
		String patternClassName = (String)migrationPatterns.get(oldVersion.toString());
		while (patternClassName != null)
		{
			try
			{
				MigrationPattern migration = (MigrationPattern)Class.forName(patternClassName).newInstance();
				migration.migrate(converter);

				//
				// get the next migration pattern
				//
				patternClassName = (String)migrationPatterns.get(migration.toVersion());
			}
			catch (ClassNotFoundException e)
			{
				throw new MigrationException();
			}
			catch (InstantiationException e)
			{
				throw new MigrationException(e);
			}
			catch (IllegalAccessException e)
			{
				throw new MigrationException(e);
			}
		}
	}
}