/*
    * 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.proxy.frontend.mysql.command.query.text.query;
  
  import lombok.Getter;
  import org.apache.shardingsphere.db.protocol.mysql.constant.MySQLConstants;
  import org.apache.shardingsphere.db.protocol.mysql.packet.MySQLPacket;
  import org.apache.shardingsphere.db.protocol.mysql.packet.command.admin.MySQLComSetOptionPacket;
  import org.apache.shardingsphere.db.protocol.mysql.packet.command.query.text.MySQLTextResultSetRowPacket;
  import org.apache.shardingsphere.db.protocol.mysql.packet.command.query.text.query.MySQLComQueryPacket;
  import org.apache.shardingsphere.db.protocol.packet.DatabasePacket;
  import org.apache.shardingsphere.infra.database.core.type.DatabaseType;
  import org.apache.shardingsphere.infra.spi.type.typed.TypedSPILoader;
  import org.apache.shardingsphere.proxy.backend.handler.ProxyBackendHandler;
  import org.apache.shardingsphere.proxy.backend.handler.ProxyBackendHandlerFactory;
  import org.apache.shardingsphere.proxy.backend.handler.ProxySQLComQueryParser;
  import org.apache.shardingsphere.proxy.backend.response.header.ResponseHeader;
  import org.apache.shardingsphere.proxy.backend.response.header.query.QueryResponseHeader;
  import org.apache.shardingsphere.proxy.backend.response.header.update.UpdateResponseHeader;
  import org.apache.shardingsphere.proxy.backend.session.ConnectionSession;
  import org.apache.shardingsphere.proxy.frontend.command.executor.QueryCommandExecutor;
  import org.apache.shardingsphere.proxy.frontend.command.executor.ResponseType;
  import org.apache.shardingsphere.proxy.frontend.mysql.command.ServerStatusFlagCalculator;
  import org.apache.shardingsphere.proxy.frontend.mysql.command.query.builder.ResponsePacketBuilder;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.SQLStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.DeleteStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.UpdateStatement;
  
  import java.sql.SQLException;
  import java.util.Collection;
  
  /**
   * COM_QUERY command packet executor for MySQL.
   */
  public final class MySQLComQueryPacketExecutor implements QueryCommandExecutor {
      
      private final ConnectionSession connectionSession;
      
      private final ProxyBackendHandler proxyBackendHandler;
      
      private final int characterSet;
      
      @Getter
      private volatile ResponseType responseType;
      
      public MySQLComQueryPacketExecutor(final MySQLComQueryPacket packet, final ConnectionSession connectionSession) throws SQLException {
          this.connectionSession = connectionSession;
          DatabaseType databaseType = TypedSPILoader.getService(DatabaseType.class, "MySQL");
          SQLStatement sqlStatement = ProxySQLComQueryParser.parse(packet.getSQL(), databaseType, connectionSession);
          proxyBackendHandler = areMultiStatements(connectionSession, sqlStatement, packet.getSQL()) ? new MySQLMultiStatementsHandler(connectionSession, sqlStatement, packet.getSQL())
                  : ProxyBackendHandlerFactory.newInstance(databaseType, packet.getSQL(), sqlStatement, connectionSession, packet.getHintValueContext());
          characterSet = connectionSession.getAttributeMap().attr(MySQLConstants.MYSQL_CHARACTER_SET_ATTRIBUTE_KEY).get().getId();
      }
      
      private boolean areMultiStatements(final ConnectionSession connectionSession, final SQLStatement sqlStatement, final String sql) {
          // TODO Multi statements should be identified by SQL Parser instead of checking if sql contains ";".
          return isMultiStatementsEnabled(connectionSession) && isSuitableMultiStatementsSQLStatement(sqlStatement) && sql.contains(";");
      }
      
      private boolean isMultiStatementsEnabled(final ConnectionSession connectionSession) {
          return connectionSession.getAttributeMap().hasAttr(MySQLConstants.MYSQL_OPTION_MULTI_STATEMENTS)
                  && MySQLComSetOptionPacket.MYSQL_OPTION_MULTI_STATEMENTS_ON == connectionSession.getAttributeMap().attr(MySQLConstants.MYSQL_OPTION_MULTI_STATEMENTS).get();
      }
      
      private boolean isSuitableMultiStatementsSQLStatement(final SQLStatement sqlStatement) {
          return sqlStatement instanceof UpdateStatement || sqlStatement instanceof DeleteStatement;
      }
      
      @Override
      public Collection<DatabasePacket> execute() throws SQLException {
          ResponseHeader responseHeader = proxyBackendHandler.execute();
          if (responseHeader instanceof QueryResponseHeader) {
              return processQuery((QueryResponseHeader) responseHeader);
          }
          responseType = ResponseType.UPDATE;
          return processUpdate((UpdateResponseHeader) responseHeader);
      }
      
      private Collection<DatabasePacket> processQuery(final QueryResponseHeader queryResponseHeader) {
          responseType = ResponseType.QUERY;
          return ResponsePacketBuilder.buildQueryResponsePackets(queryResponseHeader, characterSet, ServerStatusFlagCalculator.calculateFor(connectionSession));
      }
      
      private Collection<DatabasePacket> processUpdate(final UpdateResponseHeader updateResponseHeader) {
         return ResponsePacketBuilder.buildUpdateResponsePackets(updateResponseHeader, ServerStatusFlagCalculator.calculateFor(connectionSession));
     }
     
     @Override
     public boolean next() throws SQLException {
         return proxyBackendHandler.next();
     }
     
     @Override
     public MySQLPacket getQueryRowPacket() throws SQLException {
         return new MySQLTextResultSetRowPacket(proxyBackendHandler.getRowData().getData());
     }
     
     @Override
     public void close() throws SQLException {
         proxyBackendHandler.close();
     }
 }