/*
 * Copyright 2002-2004 the original author or authors.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */ 

package org.springframework.jdbc.support;

import java.sql.DatabaseMetaData;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import javax.sql.DataSource;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

/**
 * Factory for creating SQLErrorCodes based on the
 * "databaseProductName" taken from the DatabaseMetaData.
 *
 * <p>Returns SQLErrorCodes populated with vendor codes
 * defined in a configuration file named "sql-error-codes.xml".
 * Reads the default file in this package if not overridden by a file in
 * the root of the class path (e.g. in the "/WEB-INF/classes" directory).
 *
 * @author Thomas Risberg
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @version $Id: SQLErrorCodesFactory.java,v 1.15 2004/05/30 15:14:26 jhoeller Exp $
 * @see java.sql.DatabaseMetaData#getDatabaseProductName
 */
public class SQLErrorCodesFactory {

	protected static final Log logger = LogFactory.getLog(SQLErrorCodesFactory.class);

	/**
	 * Name of custom SQL error codes file, loading from the root
	 * of the class path (e.g. in the WEB-INF/classes directory).
	 */
	public static final String SQL_ERROR_CODE_OVERRIDE_PATH = "sql-error-codes.xml";

	/**
	 * Name of default SQL error code files, loading from the class path.
	 */
	public static final String SQL_ERROR_CODE_DEFAULT_PATH = "org/springframework/jdbc/support/sql-error-codes.xml";

	/**
	 * Keep track of a single instance so we can return it to classes that request it.
	 */
	private static final SQLErrorCodesFactory instance = new SQLErrorCodesFactory();

	/**
	 * Return singleton instance.
	 */
	public static SQLErrorCodesFactory getInstance() {
		return instance;
	}


	/**
	 * Map to hold database product name retrieved from database metadata.
	 * Key is the DataSource, value is the database product name.
	 */
	private final Map dataSourceProductName = new HashMap(10);

	/**
	 * Map to hold error codes for all databases defined in the config file.
	 * Key is the database product name, value is the SQLErrorCodes instance.
	 */
	private final Map rdbmsErrorCodes;

	/**
	 * Not public to enforce Singleton design pattern.
	 * Would be private except to allow testing via overriding
	 * the loadResource method.
	 * <b>Do not subclass in application code.</b>
	 * @see #loadResource
	 */
	protected SQLErrorCodesFactory() {
		Map errorCodes = null;

		try {
			String path = SQL_ERROR_CODE_OVERRIDE_PATH;
			Resource resource = loadResource(path);
			if (resource == null || !resource.exists()) {
				path = SQL_ERROR_CODE_DEFAULT_PATH;
				resource = loadResource(path);
				if (resource == null || !resource.exists()) {
					throw new BeanDefinitionStoreException("Unable to locate file [" + SQL_ERROR_CODE_DEFAULT_PATH  + "]");
				}
			}
			ListableBeanFactory bf = new XmlBeanFactory(resource);
			String[] rdbmsNames = bf.getBeanDefinitionNames(SQLErrorCodes.class);
			errorCodes = new HashMap(rdbmsNames.length);

			for (int i = 0; i < rdbmsNames.length; i++) {
				SQLErrorCodes ec = (SQLErrorCodes) bf.getBean(rdbmsNames[i]);
				if (ec.getBadSqlGrammarCodes() == null) {
					ec.setBadSqlGrammarCodes(new String[0]);
				}
				else {
					Arrays.sort(ec.getBadSqlGrammarCodes());
				}
				if (ec.getDataIntegrityViolationCodes() == null) {
					ec.setDataIntegrityViolationCodes(new String[0]);
				}
				else {
					Arrays.sort(ec.getDataIntegrityViolationCodes());
				}
				if (ec.getDatabaseProductName() == null) {
					errorCodes.put(rdbmsNames[i], ec);
				}
				else {
					errorCodes.put(ec.getDatabaseProductName(), ec);
				}
			}
			logger.info("SQLErrorCodes loaded: " + errorCodes.keySet());
		}
		catch (BeanDefinitionStoreException ex) {
			logger.warn("Error loading error codes from config file. Message: " + ex.getMessage());
			errorCodes = new HashMap(0);
		}

		this.rdbmsErrorCodes = errorCodes;
	}
	
	/**
	 * Protected for testability. Load the given resource from the class path.
	 * @param path resource path. SQL_ERROR_CODE_DEFAULT_PATH or
	 * SQL_ERROR_CODE_OVERRIDE_PATH.
	 * <b>Not to be overriden by application developers, who should obtain instances
	 * of this class from the static getInstance() method.</b>
	 * @return the input stream or null if the resource wasn't found
	 * @see #getInstance
	 */
	protected Resource loadResource(String path) {
		return new ClassPathResource(path);
	}

	/**
	 * Return SQLErrorCodes for the given DataSource,
	 * evaluating databaseProductName from DatabaseMetaData,
	 * or an empty error codes instance if no SQLErrorCodes were found.
	 * @see java.sql.DatabaseMetaData#getDatabaseProductName
	 */
	public SQLErrorCodes getErrorCodes(DataSource ds) {
		logger.info("Looking up default SQLErrorCodes for DataSource");
		
		// Let's avoid looking up database product info if we can.
		String dataSourceDbName = (String) this.dataSourceProductName.get(ds);
		if (dataSourceDbName != null) {
			logger.info("Database product name found in cache for DataSource [" +
			            ds + "]. Name is '" + dataSourceDbName + "'.");
			return getErrorCodes(dataSourceDbName);
		}

		// We could not find it - got to look it up.
		try {
			Map dbmdInfo = (Map) JdbcUtils.extractDatabaseMetaData(ds, new DatabaseMetaDataCallback() {
				public Object processMetaData(DatabaseMetaData dbmd) throws SQLException {
					Map info = new HashMap(2);
					if (dbmd != null) {
						info.put("DatabaseProductName", dbmd.getDatabaseProductName());
						info.put("DriverVersion", dbmd.getDriverVersion());
					}
					return info;
				}
			});
			if (dbmdInfo != null) {
				// should always be the case outside of test environments
				String dbName = (String) dbmdInfo.get("DatabaseProductName");
				String driverVersion = (String) dbmdInfo.get("DriverVersion");
				// special check for DB2
				if (dbName != null && dbName.startsWith("DB2/")) {
					dbName = "DB2";
				}
				if (dbName != null) {
					this.dataSourceProductName.put(ds, dbName);
					logger.info("Database Product Name is " + dbName);
					logger.info("Driver Version is " + driverVersion);
					SQLErrorCodes sec = (SQLErrorCodes) this.rdbmsErrorCodes.get(dbName);
					if (sec != null) {
						return sec;
					}
					logger.info("Error Codes for " + dbName + " not found");
				}
			}
		}
		catch (MetaDataAccessException ex) {
			logger.warn("Error while getting database metadata", ex);
		}

		// fallback is to return an empty ErrorCodes instance
		return new SQLErrorCodes();
	}

	/**
	 * Return SQLErrorCodes instance for the given database.
	 * No need for a  database metadata lookup.
	 */
	public SQLErrorCodes getErrorCodes(String dbName) {
		SQLErrorCodes sec = (SQLErrorCodes) this.rdbmsErrorCodes.get(dbName);
		if (sec == null) {
			// could not find the database among the defined ones
			sec = new SQLErrorCodes();
		}
		return sec;
	}

}