content: /*
   * Copyright (C) 2016-2023 ActionTech.
   * based on code by MyCATCopyrightHolder Copyright (c) 2013, OpenCloudDB/MyCAT.
   * License: http://www.gnu.org/licenses/gpl.html GPL version 2 or higher.
   */
  package com.actiontech.dble.server.response;
  
  import com.actiontech.dble.backend.mysql.PacketUtil;
  import com.actiontech.dble.backend.mysql.VersionUtil;
  import com.actiontech.dble.config.Fields;
  import com.actiontech.dble.config.model.SystemConfig;
  import com.actiontech.dble.config.model.user.UserConfig;
  import com.actiontech.dble.net.mysql.*;
  import com.actiontech.dble.services.FrontendService;
  import com.actiontech.dble.services.mysqlsharding.ShardingService;
  import com.google.common.base.Splitter;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.nio.ByteBuffer;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  /**
   * @author mycat
   */
  public final class SelectVariables {
      private SelectVariables() {
      }
  
      private static final Logger LOGGER = LoggerFactory.getLogger(SelectVariables.class);
  
  
      public static <T extends UserConfig> void execute(FrontendService<T> service, String sql) {
          String subSql = sql.substring(sql.indexOf("SELECT") + 6);
          List<String> splitVar = Splitter.on(",").omitEmptyStrings().trimResults().splitToList(subSql);
          splitVar = convert(splitVar);
          int fieldCount = splitVar.size();
          ResultSetHeaderPacket header = PacketUtil.getHeader(fieldCount);
          FieldPacket[] fields = new FieldPacket[fieldCount];
  
          int i = 0;
          header.setPacketId(service.nextPacketId());
          for (String s : splitVar) {
              fields[i] = PacketUtil.getField(s, Fields.FIELD_TYPE_VAR_STRING);
              fields[i++].setPacketId(service.nextPacketId());
          }
  
  
          ByteBuffer buffer = service.allocate();
  
          // writeDirectly header
          buffer = header.write(buffer, service, true);
  
          // writeDirectly fields
          for (FieldPacket field : fields) {
              buffer = field.write(buffer, service, true);
          }
  
  
          EOFPacket eof = new EOFPacket();
          eof.setPacketId(service.nextPacketId());
          // writeDirectly eof
          buffer = eof.write(buffer, service, true);
  
          // writeDirectly rows
          //byte packetId = eof.packetId;
  
          RowDataPacket row = new RowDataPacket(fieldCount);
          for (String s : splitVar) {
              switch (s.toLowerCase()) {
                  case "character_set_client":
                      row.add(service.getCharset().getClient() != null ? service.getCharset().getClient().getBytes() : null);
                      break;
                  case "character_set_results":
                      row.add(service.getCharset().getResults() != null ? service.getCharset().getResults().getBytes() : null);
                      break;
                  case "collation_connection":
                      row.add(service.getCharset().getCollation() != null ? service.getCharset().getCollation().getBytes() : null);
                      break;
                  case "max_allowed_packet":
                  case "@@max_allowed_packet":
                      row.add(String.valueOf(SystemConfig.getInstance().getMaxPacketSize()).getBytes());
                      break;
                  default:
                      String value = VARIABLES.get(s) == null ? "" : VARIABLES.get(s);
                      row.add(value.getBytes());
              }
  
          }
  
          row.setPacketId(service.nextPacketId());
          buffer = row.write(buffer, service, true);
  
  
          // writeDirectly lastEof
          EOFRowPacket lastEof = new EOFRowPacket();
          lastEof.setPacketId(service.nextPacketId());
          lastEof.write(buffer, service);
      }
  
      private static List<String> convert(List<String> in) {
          List<String> out = new ArrayList<>();
          for (String s : in) {
              int asIndex = s.toUpperCase().indexOf(" AS ");
              if (asIndex != -1) {
                  out.add(s.substring(asIndex + 4));
              }
          }
          if (out.isEmpty()) {
              return in;
          } else {
              return out;
          }
  
  
      }
  
  
      private static final Map<String, String> VARIABLES = new HashMap<>();
  
      static {
          VARIABLES.put("@@character_set_client", "utf8mb4");
          VARIABLES.put("@@character_set_connection", "utf8mb4");
          VARIABLES.put("@@character_set_results", "utf8mb4");
          VARIABLES.put("@@character_set_server", "utf8mb4");
          VARIABLES.put("@@init_connect", "");
          VARIABLES.put("@@interactive_timeout", "172800");
          VARIABLES.put("@@license", "GPL");
          VARIABLES.put("@@lower_case_table_names", "1");
          VARIABLES.put("@@net_buffer_length", "16384");
          VARIABLES.put("@@net_write_timeout", "60");
          VARIABLES.put("@@query_cache_size", "0");
          VARIABLES.put("@@query_cache_type", "OFF");
          VARIABLES.put("@@sql_mode", "STRICT_TRANS_TABLES");
          VARIABLES.put("@@system_time_zone", "CST");
          VARIABLES.put("@@time_zone", "SYSTEM");
          VARIABLES.put("@@" + VersionUtil.TRANSACTION_ISOLATION, "REPEATABLE-READ");
          VARIABLES.put("@@" + VersionUtil.TX_ISOLATION, "REPEATABLE-READ");
          VARIABLES.put("@@wait_timeout", "172800");
          VARIABLES.put("@@session.auto_increment_increment", "1");
  
          VARIABLES.put("character_set_client", "utf8mb4");
          VARIABLES.put("character_set_connection", "utf8mb4");
          VARIABLES.put("character_set_results", "utf8mb4");
          VARIABLES.put("character_set_server", "utf8mb4");
          VARIABLES.put("init_connect", "");
          VARIABLES.put("interactive_timeout", "172800");
          VARIABLES.put("license", "GPL");
          VARIABLES.put("lower_case_table_names", "1");
          VARIABLES.put("net_buffer_length", "16384");
          VARIABLES.put("net_write_timeout", "60");
          VARIABLES.put("query_cache_size", "0");
          VARIABLES.put("query_cache_type", "OFF");
          VARIABLES.put("sql_mode", "STRICT_TRANS_TABLES");
          VARIABLES.put("system_time_zone", "CST");
          VARIABLES.put("time_zone", "SYSTEM");
          VARIABLES.put(VersionUtil.TRANSACTION_ISOLATION, "REPEATABLE-READ");
          VARIABLES.put(VersionUtil.TX_ISOLATION, "REPEATABLE-READ");
          VARIABLES.put("wait_timeout", "172800");
          VARIABLES.put("auto_increment_increment", "1");
      }
  
  
      public static byte setCurrentPacket(ShardingService service) {
          byte packetId = (byte) service.getSession2().getPacketId().get();
          return packetId;
      }
  
  
  }
  