// This Source Code is in the Public Domain per: http://litesoft.org/License.txt
package org.litesoft.sql;

import java.util.*;

import org.litesoft.core.typeutils.*;
import org.litesoft.db.*;
import org.litesoft.logger.*;

public class SQLProductSpecificHelperManager
{
    public static final Logger LOGGER = LoggerFactory.getLogger( SQLProductSpecificHelperManager.class );

    private SQLProductSpecificHelperManager()
    {
    }

    public static synchronized SQLProductSpecificHelper getVendorSpecificHelperFor( DBinfo pDBinfo )
            throws DBException
    {
        SQLProductSpecificHelper specificHelper = HELPERS.get( pDBinfo.toString() );
        if ( specificHelper == null )
        {
            if ( null == (specificHelper = HELPERS.get( pDBinfo.getProductName() )) )
            {
                String nomName = className( pDBinfo.toString() );
                if ( null == (specificHelper = load( nomName )) )
                {
                    if ( null == (specificHelper = load( nomName = className( pDBinfo.getProductName() ) )) )
                    {
                        throw new DisplayableDBException( "UnableLoadSQLProductSpecificHelper", pDBinfo.getProductName(), pDBinfo.getProductVersion() );
                    }
                }
                HELPERS.put( nomName, specificHelper );
            }
        }
        return specificHelper;
    }

    private static final Map<String, SQLProductSpecificHelper> HELPERS = new HashMap<String, SQLProductSpecificHelper>();

    private static String className( String pString )
    {
        StringBuilder sb = new StringBuilder( pString );
        for ( int i = 0; i < sb.length(); i++ )
        {
            char c = sb.charAt( i );
            if ( !Characters.isAlphaNumeric( c ) )
            {
                sb.setCharAt( i, '_' );
            }
        }
        return sb.toString();
    }

    private static SQLProductSpecificHelper load( String pNomName )
    {
        Class<SQLProductSpecificHelper> zClass = SQLProductSpecificHelper.class;
        String classNameToLoad = zClass.getName();
        String toLoad = classNameToLoad + pNomName;
        try
        {
            Class targetClass = zClass.getClassLoader().loadClass( toLoad );
            if ( SQLProductSpecificHelper.class.isAssignableFrom( targetClass ) )
            {
                return (SQLProductSpecificHelper) targetClass.newInstance();
            }
            LOGGER.error.log( toLoad, " does NOT implement ", classNameToLoad );
        }
        catch ( ClassNotFoundException e )
        {
            return null; // Normal Behavior
        }
        catch ( IllegalAccessException e )
        {
            LOGGER.error.log( e, "Unable To Load ", toLoad );
        }
        catch ( InstantiationException e )
        {
            LOGGER.error.log( e, "Unable To Load ", toLoad );
        }
        return null;
    }
}