selfprivacy.org.app/lib/logic/api_maps/server.dart

import 'dart:convert';
import 'dart:io';

import 'package:dio/dio.dart';

import 'api_map.dart';

class ServerApi extends ApiMap {
  ServerApi(String domainName) {
    loggedClient.options = BaseOptions(
      baseUrl: 'https://api.$domainName',
    );
  }

  Future<bool> isHttpServerWorking() async {
    bool res;

    Response response;
    try {
      response = await loggedClient.get('/serviceStatus');
      res = response.statusCode == HttpStatus.ok;
    } catch (e) {
      res = false;
    }

    return res;
  }

  Future<String> getDkim(String domainName) async {
    var response = await loggedClient.get(
      '/getDKIM',
      options: Options(responseType: ResponseType.plain),
    );
    return _decodeAndCutData(response.data, domainName);
  }
}

String _decodeAndCutData(String text, String domainName) {
  var decodedTextString = text.substring(1, text.length - 1);
  var stringToBase64 = utf8.fuse(base64);

  return stringToBase64
      .decode(decodedTextString)
      .replaceAll("selector._domainkey	IN	TXT	( ", "")
      .replaceAll("\"\n	  \"", "")
      .replaceAll(' )  ; ----- DKIM key selector for $domainName\n', '');
}