/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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.apache.shardingsphere.infra.database.mysql.checker;
  
  import org.apache.shardingsphere.infra.database.core.checker.DialectDatabasePrivilegeChecker;
  import org.apache.shardingsphere.infra.database.core.checker.PrivilegeCheckType;
  import org.apache.shardingsphere.infra.database.core.exception.CheckDatabaseEnvironmentFailedException;
  import org.apache.shardingsphere.infra.database.core.exception.MissingRequiredPrivilegeException;
  
  import javax.sql.DataSource;
  import java.sql.Connection;
  import java.sql.PreparedStatement;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.EnumMap;
  import java.util.Map;
  
  /**
   * Database environment checker for MySQL.
   */
  public final class MySQLDatabasePrivilegeChecker implements DialectDatabasePrivilegeChecker {
      
      private static final String SHOW_GRANTS_SQL = "SHOW GRANTS";
      
      private static final int MYSQL_MAJOR_VERSION_8 = 8;
      
      // BINLOG MONITOR is a synonym for REPLICATION CLIENT for MariaDB
      private static final String[][] PIPELINE_REQUIRED_PRIVILEGES =
              {{"ALL PRIVILEGES", "ON *.*"}, {"REPLICATION SLAVE", "REPLICATION CLIENT", "ON *.*"}, {"REPLICATION SLAVE", "BINLOG MONITOR", "ON *.*"}};
      
      private static final String[][] XA_REQUIRED_PRIVILEGES = {{"ALL PRIVILEGES", "ON *.*"}, {"XA_RECOVER_ADMIN", "ON *.*"}};
      
      private static final Map<PrivilegeCheckType, Collection<String>> REQUIRED_PRIVILEGES_FOR_MESSAGE = new EnumMap<>(PrivilegeCheckType.class);
      
      static {
          REQUIRED_PRIVILEGES_FOR_MESSAGE.put(PrivilegeCheckType.PIPELINE, Arrays.asList("REPLICATION SLAVE", "REPLICATION CLIENT"));
          REQUIRED_PRIVILEGES_FOR_MESSAGE.put(PrivilegeCheckType.SELECT, Collections.singleton("SELECT ON DATABASE"));
          REQUIRED_PRIVILEGES_FOR_MESSAGE.put(PrivilegeCheckType.XA, Collections.singleton("XA_RECOVER_ADMIN"));
      }
      
      @Override
      public void check(final DataSource dataSource, final PrivilegeCheckType privilegeCheckType) {
          try (Connection connection = dataSource.getConnection()) {
              if (PrivilegeCheckType.XA == privilegeCheckType && MYSQL_MAJOR_VERSION_8 != connection.getMetaData().getDatabaseMajorVersion()) {
                  return;
              }
              checkPrivilege(connection, privilegeCheckType);
          } catch (final SQLException ex) {
              throw new CheckDatabaseEnvironmentFailedException(ex);
          }
      }
      
      private void checkPrivilege(final Connection connection, final PrivilegeCheckType privilegeCheckType) {
          try (
                  PreparedStatement preparedStatement = connection.prepareStatement(SHOW_GRANTS_SQL);
                  ResultSet resultSet = preparedStatement.executeQuery()) {
              while (resultSet.next()) {
                  String privilege = resultSet.getString(1).toUpperCase();
                  if (matchPrivileges(privilege, getRequiredPrivileges(connection, privilegeCheckType))) {
                      return;
                  }
              }
          } catch (final SQLException ex) {
              throw new CheckDatabaseEnvironmentFailedException(ex);
          }
          throw new MissingRequiredPrivilegeException(REQUIRED_PRIVILEGES_FOR_MESSAGE.get(privilegeCheckType));
      }
      
      private String[][] getRequiredPrivileges(final Connection connection, final PrivilegeCheckType privilegeCheckType) throws SQLException {
          switch (privilegeCheckType) {
              case PIPELINE:
                  return PIPELINE_REQUIRED_PRIVILEGES;
              case SELECT:
                  return getSelectRequiredPrivilege(connection);
              case XA:
                  return XA_REQUIRED_PRIVILEGES;
              default:
                  return new String[0][0];
          }
      }
      
     private String[][] getSelectRequiredPrivilege(final Connection connection) throws SQLException {
         String onCatalog = String.format("ON `%s`.*", connection.getCatalog().toUpperCase());
         return new String[][]{{"ALL PRIVILEGES", "ON *.*"}, {"SELECT", "ON *.*"}, {"ALL PRIVILEGES", onCatalog}, {"SELECT", onCatalog}};
     }
     
     private boolean matchPrivileges(final String grantedPrivileges, final String[][] requiredPrivileges) {
         return Arrays.stream(requiredPrivileges).anyMatch(each -> Arrays.stream(each).allMatch(grantedPrivileges::contains));
     }
     
     @Override
     public String getDatabaseType() {
         return "MySQL";
     }
 }