content: /*
   * Copyright (C) 2016-2023 ActionTech.
   * License: http://www.gnu.org/licenses/gpl.html GPL version 2 or higher.
   */
  package com.actiontech.dble.services.manager.response;
  
  import com.actiontech.dble.backend.mysql.PacketUtil;
  import com.actiontech.dble.config.Fields;
  import com.actiontech.dble.meta.ColumnMeta;
  import com.actiontech.dble.net.mysql.*;
  import com.actiontech.dble.route.parser.util.DruidUtil;
  import com.actiontech.dble.server.util.SchemaUtil;
  import com.actiontech.dble.services.manager.ManagerService;
  import com.actiontech.dble.services.manager.information.ManagerBaseTable;
  import com.actiontech.dble.services.manager.information.ManagerBaseView;
  import com.actiontech.dble.services.manager.information.ManagerSchemaInfo;
  import com.actiontech.dble.util.StringUtil;
  import com.alibaba.druid.sql.ast.SQLStatement;
  import com.alibaba.druid.sql.dialect.mysql.ast.statement.MySqlExplainStatement;
  
  import java.nio.ByteBuffer;
  import java.sql.SQLException;
  import java.util.Collection;
  
  /**
   * ShowDatabase
   *
   * @author mycat
   * @author mycat
   */
  public final class Describe {
      private Describe() {
      }
  
      private static final int FIELD_COUNT = 6;
      private static final ResultSetHeaderPacket HEADER = PacketUtil.getHeader(FIELD_COUNT);
      private static final FieldPacket[] FIELDS = new FieldPacket[FIELD_COUNT];
      private static final EOFPacket EOF = new EOFPacket();
  
      static {
          int i = 0;
          byte packetId = 0;
          HEADER.setPacketId(++packetId);
  
          FIELDS[i] = PacketUtil.getField("Field", Fields.FIELD_TYPE_VAR_STRING);
          FIELDS[i++].setPacketId(++packetId);
          FIELDS[i] = PacketUtil.getField("Type", Fields.FIELD_TYPE_VAR_STRING);
          FIELDS[i++].setPacketId(++packetId);
          FIELDS[i] = PacketUtil.getField("Null", Fields.FIELD_TYPE_VAR_STRING);
          FIELDS[i++].setPacketId(++packetId);
          FIELDS[i] = PacketUtil.getField("Key", Fields.FIELD_TYPE_VAR_STRING);
          FIELDS[i++].setPacketId(++packetId);
          FIELDS[i] = PacketUtil.getField("Default", Fields.FIELD_TYPE_VAR_STRING);
          FIELDS[i++].setPacketId(++packetId);
          FIELDS[i] = PacketUtil.getField("Extra", Fields.FIELD_TYPE_VAR_STRING);
          FIELDS[i].setPacketId(++packetId);
  
          EOF.setPacketId(++packetId);
      }
  
      public static void execute(String stmt, ManagerService service) {
          String tableName;
          try {
              SQLStatement statement = DruidUtil.parseMultiSQL(stmt);
              MySqlExplainStatement describeStatement = (MySqlExplainStatement) statement;
              SchemaUtil.SchemaInfo schemaInfo = SchemaUtil.getSchemaInfo(service.getUser(), service.getSchema(), describeStatement.getTableName(), null);
              // schemaName = schemaInfo.getSchema().toLowerCase();
              tableName = schemaInfo.getTable().toLowerCase();
          } catch (SQLException e) {
              service.writeErrMessage(e.getSQLState(), e.getMessage(), e.getErrorCode());
              return;
          }
  
          ByteBuffer buffer = service.allocate();
  
          // write header
          buffer = HEADER.write(buffer, service, true);
  
          // write fields
          for (FieldPacket field : FIELDS) {
              buffer = field.write(buffer, service, true);
          }
  
          // write eof
          buffer = EOF.write(buffer, service, true);
  
          // write rows
          byte packetId = EOF.getPacketId();
  
          ManagerBaseTable table = ManagerSchemaInfo.getInstance().getTables().get(tableName);
          Collection<ColumnMeta> columns;
          if (table != null) {
              columns = table.getColumnsMeta();
          } else {
              ManagerBaseView view = ManagerSchemaInfo.getInstance().getView(tableName);
              columns = view.getColumnsMeta();
          }
  
          for (ColumnMeta column : columns) {
              RowDataPacket row = new RowDataPacket(FIELD_COUNT);
              row.add(StringUtil.encode(column.getName(), service.getCharset().getResults()));
              row.add(StringUtil.encode(column.getDataType(), service.getCharset().getResults()));
              row.add(StringUtil.encode(column.isCanNull() ? "YES" : "NO", service.getCharset().getResults()));
              row.add(StringUtil.encode(column.isPrimaryKey() ? "PRI" : "", service.getCharset().getResults()));
              row.add(StringUtil.encode(column.getDefaultVal(), service.getCharset().getResults()));
              row.add(StringUtil.encode("", service.getCharset().getResults()));
              row.setPacketId(++packetId);
              buffer = row.write(buffer, service, true);
          }
  
          // write lastEof
          EOFRowPacket lastEof = new EOFRowPacket();
          lastEof.setPacketId(++packetId);
          // write buffer
          lastEof.write(buffer, service);
      }
  
  }
  