private string ParseConnectionString()

in MySQL.Data/src/X/XDevAPI/BaseSession.cs [695:753]
46 lines of code
21 McCabe index (conditional complexity)

    private string ParseConnectionString(string connectionString)
    {
      var updatedConnectionString = string.Empty;
      bool portProvided = false;
      bool isDnsSrv = false;
      var connectionOptionsDictionary = connectionString.Split(CONNECTION_DATA_KEY_SEPARATOR)
                .Select(item => item.Split(new char[] { CONNECTION_DATA_VALUE_SEPARATOR }, 2))
                .Where(item => item.Length == 2)
                .ToDictionary(item => item[0], item => item[1]);
      var serverOption = MySqlXConnectionStringBuilder.Options.Options.First(item => item.Keyword == SERVER_CONNECTION_OPTION_KEYWORD);
      var connecttimeoutOption = MySqlXConnectionStringBuilder.Options.Options.First(item => item.Keyword == CONNECT_TIMEOUT_CONNECTION_OPTION_KEYWORD);
      foreach (KeyValuePair<string, string> keyValuePair in connectionOptionsDictionary)
      {
        // Value is an equal or a semicolon
        if (keyValuePair.Value == "=" || keyValuePair.Value == "\"")
          throw new MySqlException(string.Format(Resources.InvalidConnectionStringValue, (keyValuePair.Value == "\"" ? ";" : "="), keyValuePair.Key));

        // Key is not server or any of its synonyms.
        if (keyValuePair.Key != serverOption.Keyword && !serverOption.Synonyms.Contains(keyValuePair.Key))
        {
          if ((connecttimeoutOption.Keyword == keyValuePair.Key || connecttimeoutOption.Synonyms.Contains(keyValuePair.Key)) &&
            String.IsNullOrWhiteSpace(keyValuePair.Value))
            throw new FormatException(ResourcesX.InvalidConnectionTimeoutValue);
          if (keyValuePair.Key == PORT_CONNECTION_OPTION_KEYWORD)
            portProvided = true;
          if (keyValuePair.Key == DNS_SRV_CONNECTION_OPTION_KEYWORD)
            isDnsSrv = Convert.ToBoolean(keyValuePair.Value);

          updatedConnectionString += $"{keyValuePair.Key}{CONNECTION_DATA_VALUE_SEPARATOR}{keyValuePair.Value}{CONNECTION_DATA_KEY_SEPARATOR}";
          continue;
        }

        // Key is server or one of its synonyms.
        var updatedValue = keyValuePair.Value;
        if (IsUnixSocket(keyValuePair.Value))
          updatedValue = NormalizeUnixSocket(keyValuePair.Value);

        // The value for the server connection option doesn't have a server list format.
        if (FailoverManager.ParseHostList(updatedValue, true, false) == 1 && FailoverManager.FailoverGroup == null)
          updatedConnectionString = $"{SERVER_CONNECTION_OPTION_KEYWORD}{CONNECTION_DATA_VALUE_SEPARATOR}{updatedValue}{CONNECTION_DATA_KEY_SEPARATOR}{updatedConnectionString}";
      }

      // DNS SRV Validation - Port cannot be provided by the user and multihost is not allowed if dns-srv is true
      if (isDnsSrv)
      {
        if (portProvided)
          throw new ArgumentException(Resources.DnsSrvInvalidConnOptionPort);
        if (FailoverManager.FailoverGroup != null)
          throw new ArgumentException(Resources.DnsSrvInvalidConnOptionMultihost);
      }

      // Default port must be added if not provided by the user.
      if (FailoverManager.FailoverGroup == null)
        return portProvided ? updatedConnectionString : $"{updatedConnectionString}{CONNECTION_DATA_KEY_SEPARATOR}{PORT_CONNECTION_OPTION_KEYWORD}{CONNECTION_DATA_VALUE_SEPARATOR}{X_PROTOCOL_DEFAULT_PORT}";

      return $"{SERVER_CONNECTION_OPTION_KEYWORD}{CONNECTION_DATA_VALUE_SEPARATOR}{FailoverManager.FailoverGroup.ActiveHost.Host}{CONNECTION_DATA_KEY_SEPARATOR}" +
        (!portProvided ? $"{PORT_CONNECTION_OPTION_KEYWORD}{CONNECTION_DATA_VALUE_SEPARATOR}{X_PROTOCOL_DEFAULT_PORT}{CONNECTION_DATA_KEY_SEPARATOR}" : string.Empty) +
        updatedConnectionString;
    }