content: /*
   * Copyright (C) 2016-2023 ActionTech.
   * License: http://www.gnu.org/licenses/gpl.html GPL version 2 or higher.
   */
  
  package com.actiontech.dble.route.parser;
  
  import com.actiontech.dble.backend.mysql.VersionUtil;
  import com.actiontech.dble.route.parser.util.ParseUtil;
  
  
  public final class ManagerParseSelect {
      private ManagerParseSelect() {
      }
  
      public static final int OTHER = -1;
      public static final int VERSION_COMMENT = 1;
      public static final int SESSION_TX_READ_ONLY = 2;
      public static final int MAX_ALLOWED_PACKET = 3;
      public static final int TIMEDIFF = 4;
      public static final int SESSION_TRANSACTION_READ_ONLY = 5;
  
      private static final char[] STRING_VERSION_COMMENT = "VERSION_COMMENT".toCharArray();
      private static final char[] STRING_SESSION = "SESSION.".toCharArray();
      private static final char[] STRING_SESSION_TRANSACTION_READ_ONLY = VersionUtil.TRANSACTION_READ_ONLY.toUpperCase().toCharArray();
      private static final char[] STRING_SESSION_TX_READ_ONLY = VersionUtil.TX_READ_ONLY.toUpperCase().toCharArray();
      private static final char[] STRING_MAX_ALLOWED_PACKET = "MAX_ALLOWED_PACKET".toCharArray();
      private static final char[] STRING_TIMEDIFF = "TIMEDIFF(NOW(), UTC_TIMESTAMP())".toCharArray();
  
      public static int parse(String stmt, int offset) {
          int i = offset;
          for (; i < stmt.length(); i++) {
              switch (stmt.charAt(i)) {
                  case ' ':
                      continue;
                  case '/':
                  case '#':
                      i = ParseUtil.comment(stmt, i);
                      continue;
                  case 'T':
                  case 't':
                      return selectTCheck(stmt, i);
                  case '@':
                      return select2Check(stmt, i);
                  default:
                      return OTHER;
              }
          }
          return OTHER;
      }
  
      private static int selectTCheck(String stmt, int offset) {
          int length = offset + STRING_TIMEDIFF.length;
          if (stmt.length() >= length && ParseUtil.compare(stmt, offset, STRING_TIMEDIFF)) {
              if (stmt.length() > length && stmt.charAt(length) != ' ') {
                  return OTHER;
              }
              return (offset << 8) | TIMEDIFF;
          }
          return OTHER;
      }
  
      private static int select2Check(String stmt, int offset) {
          if (stmt.length() > ++offset && stmt.charAt(offset) == '@' && stmt.length() > ++offset) {
              switch (stmt.charAt(offset)) {
                  case 'S':
                  case 's':
                      return select2SCheck(stmt, offset);
                  case 'V':
                  case 'v':
                      return select2VCheck(stmt, offset);
                  case 'M':
                  case 'm':
                      return select2MCheck(stmt, offset);
                  default:
                      return OTHER;
              }
          }
          return OTHER;
      }
  
      private static int select2MCheck(String stmt, int offset) {
          int length = offset + STRING_MAX_ALLOWED_PACKET.length;
          if (stmt.length() >= length && ParseUtil.compare(stmt, offset, STRING_MAX_ALLOWED_PACKET)) {
              if (stmt.length() > length && stmt.charAt(length) != ' ') {
                  return OTHER;
              }
              return MAX_ALLOWED_PACKET;
          }
          return OTHER;
      }
  
      // VERSION_COMMENT
      private static int select2VCheck(String stmt, int offset) {
          int length = offset + STRING_VERSION_COMMENT.length;
          if (stmt.length() >= length && ParseUtil.compare(stmt, offset, STRING_VERSION_COMMENT)) {
              if (stmt.length() > length && stmt.charAt(length) != ' ') {
                  return OTHER;
              }
              return VERSION_COMMENT;
          }
          return OTHER;
      }
  
      // SESSION.
      private static int select2SCheck(String stmt, int offset) {
          int length = offset + STRING_SESSION.length;
          if (stmt.length() < length + 2) { //session.tx
              return OTHER;
          }
          if (ParseUtil.compare(stmt, offset, STRING_SESSION)) {
              if (ParseUtil.isEOF(stmt, length)) {
                  return OTHER;
              }
          } else {
              return OTHER;
          }
          offset = offset + STRING_SESSION.length;
          switch (stmt.charAt(offset)) {
              case 'T':
              case 't':
                  switch (stmt.charAt(offset + 1)) {
                      case 'X':
                      case 'x':
                          return select2TXCheck(stmt, offset);
                      case 'R':
                      case 'r':
                          return select2TRCheck(stmt, offset);
                      default:
                          return OTHER;
                  }
              default:
                  return OTHER;
          }
      }
  
      // SESSION.TX_READ_ONLY
      private static int select2TXCheck(String stmt, int offset) {
          int length = offset + STRING_SESSION_TX_READ_ONLY.length;
          if (stmt.length() >= length && ParseUtil.compare(stmt, offset, STRING_SESSION_TX_READ_ONLY)) {
              if (!ParseUtil.isEOF(stmt, length)) {
                  return OTHER;
              }
              return SESSION_TX_READ_ONLY;
          }
  
          return OTHER;
      }
  
      // SESSION.TRANSACTION_READ_ONLY
      private static int select2TRCheck(String stmt, int offset) {
          int length = offset + STRING_SESSION_TRANSACTION_READ_ONLY.length;
          if (stmt.length() >= length && ParseUtil.compare(stmt, offset, STRING_SESSION_TRANSACTION_READ_ONLY)) {
              if (!ParseUtil.isEOF(stmt, length)) {
                  return OTHER;
              }
              return SESSION_TRANSACTION_READ_ONLY;
          }
  
          return OTHER;
      }
  
  }
  