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/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * 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 software.amazon.jdbc.dialect;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Arrays;
import java.util.EnumSet;
import java.util.List;
import java.util.Properties;
import org.checkerframework.checker.nullness.qual.NonNull;
import software.amazon.jdbc.HostSpec;
import software.amazon.jdbc.exceptions.ExceptionHandler;
import software.amazon.jdbc.exceptions.MySQLExceptionHandler;
import software.amazon.jdbc.hostlistprovider.ConnectionStringHostListProvider;
import software.amazon.jdbc.plugin.failover.FailoverRestriction;

public class MysqlDialect implements Dialect {

  private static final List dialectUpdateCandidates = Arrays.asList(
      DialectCodes.RDS_MULTI_AZ_MYSQL_CLUSTER,
      DialectCodes.AURORA_MYSQL,
      DialectCodes.RDS_MYSQL
  );
  private static MySQLExceptionHandler mySQLExceptionHandler;

  private static final EnumSet NO_RESTRICTIONS = EnumSet.noneOf(FailoverRestriction.class);

  @Override
  public int getDefaultPort() {
    return 3306;
  }

  @Override
  public ExceptionHandler getExceptionHandler() {
    if (mySQLExceptionHandler == null) {
      mySQLExceptionHandler = new MySQLExceptionHandler();
    }
    return mySQLExceptionHandler;
  }

  @Override
  public String getHostAliasQuery() {
    return "SELECT CONCAT(@@hostname, ':', @@port)";
  }

  @Override
  public String getServerVersionQuery() {
    return "SHOW VARIABLES LIKE 'version_comment'";
  }

  @Override
  public boolean isDialect(final Connection connection) {
    Statement stmt = null;
    ResultSet rs = null;
    try {
      stmt = connection.createStatement();
      rs = stmt.executeQuery(this.getServerVersionQuery());
      while (rs.next()) {
        final int columnCount = rs.getMetaData().getColumnCount();
        for (int i = 1; i <= columnCount; i++) {
          final String columnValue = rs.getString(i);
          if (columnValue != null && columnValue.toLowerCase().contains("mysql")) {
            return true;
          }
        }
      }
    } catch (final SQLException ex) {
      // ignore
    } finally {
      if (stmt != null) {
        try {
          stmt.close();
        } catch (SQLException ex) {
          // ignore
        }
      }
      if (rs != null) {
        try {
          rs.close();
        } catch (SQLException ex) {
          // ignore
        }
      }
    }
    return false;
  }

  @Override
  public List getDialectUpdateCandidates() {
    return dialectUpdateCandidates;
  }

  public HostListProviderSupplier getHostListProvider() {
    return (properties, initialUrl, hostListProviderService, pluginService) ->
        new ConnectionStringHostListProvider(properties, initialUrl, hostListProviderService);
  }

  @Override
  public void prepareConnectProperties(
      final @NonNull Properties connectProperties, final @NonNull String protocol, final @NonNull HostSpec hostSpec) {
    // do nothing
  }

  @Override
  public EnumSet getFailoverRestrictions() {
    return NO_RESTRICTIONS;
  }
}