// Copyright 2011 Google Inc.
//
// 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 com.google.enterprise.connector.database;

import com.google.common.base.Strings;

import java.util.logging.Logger;

import javax.sql.DataSource;

/**
 * Factory used to construct JDBC {@link DataSource} instances based upon
 * property values and reflection.  This class is specifically used to
 * overcome the lack of conditional bean creation in the Spring Framework.
 */
public class JdbcDataSourceFactory {
  private static final Logger LOGGER =
      Logger.getLogger(JdbcDataSourceFactory.class.getName());

  /**
   * This factory method makes an attempt to conditionally create a
   * {@link DataSource} instance based upon a property value and the
   * name of the {@link DataSource} implementation class.  If the property
   * value is non-null and non-empty, and the implementation class can be
   * found on the classpath, then an instance of that {@link DataSource}
   * implementation is created and returned; otherwise a fake (stub)
   * {@link DataSource} implementation is returned.
   *
   * @param description descriptive name of the DataSource driver to be
   *                    used in log messages.
   * @param className the name for {@link DataSource} implementation class
   * @param propertyValue the value of a configured Property
   */
  public static DataSource newJdbcDataSource(String description,
      String className, String propertyValue)
      throws InstantiationException, IllegalAccessException {

    // If the property (typically a datasource URL) is not specified,
    // then consider the DataSource to be unconfigured.  Create a stub
    // in its place.
    if (Strings.isNullOrEmpty(propertyValue)) {
      LOGGER.fine(description + " JDBC DataSource has not been configured."
                  + " Creating a disabled stub in its place.");
      return new FakeDataSource(description);
    }

    // If the DataSource implementation class can not be found on the
    // classpath, then return a disabled stub in its place.
    DataSource dataSource;
    try {
      dataSource = (DataSource) Class.forName(className).newInstance();
    } catch (ClassCastException cce) {
      LOGGER.warning(description + " JDBC DataSource implementation not a valid"
                     + " DataSource? Creating a disabled stub in its place.");
      return new FakeDataSource(description);
    } catch (ClassNotFoundException cnfe) {
      LOGGER.warning(description + " JDBC DataSource implementation not found."
                     + " Creating a disabled stub in its place.");
      return new FakeDataSource(description);
    } catch (NoClassDefFoundError ncdfe) {
      LOGGER.warning(description + " JDBC DataSource implementation not found."
                     + " Creating a disabled stub in its place.");
      return new FakeDataSource(description);
    }

    LOGGER.config(description + " JDBC DataSource created: " + dataSource);
    return dataSource;
  }
}