/**
    * Copyright 2005-2016 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.rice.krad.data.platform;
  
  import org.springframework.dao.DataAccessException;
  import org.springframework.jdbc.core.ConnectionCallback;
  import org.springframework.jdbc.core.JdbcTemplate;
  
  import javax.sql.DataSource;
  import java.sql.Connection;
  import java.sql.DatabaseMetaData;
  import java.sql.SQLException;
  import java.util.Collections;
  import java.util.IdentityHashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * Contains constants and utilities related to the supported database platforms.
   *
   * <p>
   * We use a String to represent the platform name as opposed to an Enum because this allows for the potential to
   * configure and use custom platforms at runtime without requiring internal code modification to support a new platform.
   * </p>
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public final class DatabasePlatforms {
  
      /**
       * The name of the Oracle platform.
       */
      public static final String ORACLE = "Oracle";
  
      /**
       * The name of the MySQL platform.
       */
      public static final String MYSQL = "MySQL";
  
      private static final Map<DataSource, DatabasePlatformInfo> platformCache
              = Collections.synchronizedMap(new IdentityHashMap<DataSource, DatabasePlatformInfo>(8));
  
      /**
       * Gets the platform information from the {@link DataSource}.
       *
       * @param dataSource the {@link DataSource} to consult.
       * @return the platform information from the {@link DataSource}.
       */
      public static DatabasePlatformInfo detectPlatform(DataSource dataSource) {
          if (dataSource == null) {
              throw new IllegalArgumentException("DataSource must not be null.");
          }
          DatabasePlatformInfo platformInfo = platformCache.get(dataSource);
          if (platformInfo == null) {
              JdbcTemplate template = new JdbcTemplate(dataSource);
                  platformCache.put(dataSource, template.execute(new ConnectionCallback<DatabasePlatformInfo>() {
                              @Override
                              public DatabasePlatformInfo doInConnection(
                                      Connection connection) throws SQLException, DataAccessException {
                                  DatabaseMetaData metadata = connection.getMetaData();
                                  String vendorName = metadata.getDatabaseProductName();
                                  int version = metadata.getDatabaseMajorVersion();
                                  return new DatabasePlatformInfo(vendorName, version);
                              }
                      }));
              if (platformInfo == null) {
                  platformInfo = platformCache.get(dataSource);
              }
          }
          return platformInfo;
      }
  
      /**
       * No-op constructor for final class.
       */
      private DatabasePlatforms() {}
  
  }