/*
    * 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.opengauss.command.query.simple;
  
  import lombok.Getter;
  import org.apache.shardingsphere.db.protocol.packet.DatabasePacket;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.PostgreSQLPacket;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.command.query.PostgreSQLColumnDescription;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.command.query.PostgreSQLDataRowPacket;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.command.query.PostgreSQLEmptyQueryResponsePacket;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.command.query.PostgreSQLRowDescriptionPacket;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.command.query.simple.PostgreSQLComQueryPacket;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.generic.PostgreSQLCommandCompletePacket;
  import org.apache.shardingsphere.db.protocol.postgresql.packet.handshake.PostgreSQLParameterStatusPacket;
  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.QueryHeader;
  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.postgresql.command.PortalContext;
  import org.apache.shardingsphere.proxy.frontend.postgresql.command.query.PostgreSQLCommand;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.dal.VariableAssignSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.SQLStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dal.EmptyStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dal.SetStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.tcl.CommitStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.tcl.RollbackStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.value.identifier.IdentifierValue;
  
  import java.sql.SQLException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedList;
  
  /**
   * Command query executor for openGauss.
   */
  public final class OpenGaussComQueryExecutor implements QueryCommandExecutor {
      
      private final PortalContext portalContext;
      
      private final ProxyBackendHandler proxyBackendHandler;
      
      @Getter
      private volatile ResponseType responseType;
      
      public OpenGaussComQueryExecutor(final PortalContext portalContext, final PostgreSQLComQueryPacket packet, final ConnectionSession connectionSession) throws SQLException {
          this.portalContext = portalContext;
          DatabaseType databaseType = TypedSPILoader.getService(DatabaseType.class, "openGauss");
          SQLStatement sqlStatement = ProxySQLComQueryParser.parse(packet.getSQL(), databaseType, connectionSession);
          proxyBackendHandler = ProxyBackendHandlerFactory.newInstance(databaseType, packet.getSQL(), sqlStatement, connectionSession, packet.getHintValueContext());
      }
      
      @Override
      public Collection<DatabasePacket> execute() throws SQLException {
          ResponseHeader responseHeader = proxyBackendHandler.execute();
          if (responseHeader instanceof QueryResponseHeader) {
              return Collections.singleton(createRowDescriptionPacket((QueryResponseHeader) responseHeader));
          }
          responseType = ResponseType.UPDATE;
          return createUpdatePacket((UpdateResponseHeader) responseHeader);
      }
      
      private PostgreSQLRowDescriptionPacket createRowDescriptionPacket(final QueryResponseHeader queryResponseHeader) {
          responseType = ResponseType.QUERY;
          return new PostgreSQLRowDescriptionPacket(createColumnDescriptions(queryResponseHeader));
      }
      
      private Collection<PostgreSQLColumnDescription> createColumnDescriptions(final QueryResponseHeader queryResponseHeader) {
          Collection<PostgreSQLColumnDescription> result = new LinkedList<>();
          int columnIndex = 0;
          for (QueryHeader each : queryResponseHeader.getQueryHeaders()) {
              result.add(new PostgreSQLColumnDescription(each.getColumnLabel(), ++columnIndex, each.getColumnType(), each.getColumnLength(), each.getColumnTypeName()));
          }
          return result;
      }
     
     private Collection<DatabasePacket> createUpdatePacket(final UpdateResponseHeader updateResponseHeader) throws SQLException {
         SQLStatement sqlStatement = updateResponseHeader.getSqlStatement();
         if (sqlStatement instanceof CommitStatement || sqlStatement instanceof RollbackStatement) {
             portalContext.closeAll();
         }
         if (sqlStatement instanceof SetStatement) {
             return createParameterStatusResponse((SetStatement) sqlStatement);
         }
         return Collections.singletonList(sqlStatement instanceof EmptyStatement ? new PostgreSQLEmptyQueryResponsePacket()
                 : new PostgreSQLCommandCompletePacket(PostgreSQLCommand.valueOf(sqlStatement.getClass()).map(PostgreSQLCommand::getTag).orElse(""), updateResponseHeader.getUpdateCount()));
     }
     
     private Collection<DatabasePacket> createParameterStatusResponse(final SetStatement sqlStatement) {
         Collection<DatabasePacket> result = new ArrayList<>(2);
         result.add(new PostgreSQLCommandCompletePacket("SET", 0));
         for (VariableAssignSegment each : sqlStatement.getVariableAssigns()) {
             result.add(new PostgreSQLParameterStatusPacket(each.getVariable().getVariable(), IdentifierValue.getQuotedContent(each.getAssignValue())));
         }
         return result;
     }
     
     @Override
     public boolean next() throws SQLException {
         return proxyBackendHandler.next();
     }
     
     @Override
     public PostgreSQLPacket getQueryRowPacket() throws SQLException {
         return new PostgreSQLDataRowPacket(proxyBackendHandler.getRowData().getData());
     }
     
     @Override
     public void close() throws SQLException {
         proxyBackendHandler.close();
     }
 }