ACMEClient = object
  api: ACMEApi
  key*: KeyPair
  kid*: Kid

KeyAuthorization = string

proc close(self: ACMEClient): InternalRaisesFuture[void, (CancelledError,)] {.
    stackTrace: false, ...raises: [], gcsafe, raises: [], raises: [],
    tags: [RootEffect].}

proc genKeyAuthorization(self: ACMEClient; token: string): KeyAuthorization {.
    ...raises: [], tags: [].}

proc getCertificate(self: ACMEClient; domain: api.Domain;
                    challenge: ACMEChallengeResponseWrapper): InternalRaisesFuture[
    ACMECertificateResponse, (ACMEError, CancelledError)] {.stackTrace: false,
    ...raises: [], gcsafe, raises: [], raises: [], tags: [RootEffect].}

proc getChallenge(self: ACMEClient; domains: seq[api.Domain]): InternalRaisesFuture[
    ACMEChallengeResponseWrapper, (ACMEError, CancelledError)] {.
    stackTrace: false, ...raises: [], gcsafe, raises: [], raises: [],
    tags: [RootEffect].}

proc new(T: typedesc[ACMEClient]; api: Opt[ACMEApi] = Opt.none(ACMEApi);
         key: Opt[KeyPair] = Opt.none(KeyPair);
         rng: ref HmacDrbgContext = newRng();
         acmeServerURL: Uri = parseUri(LetsEncryptURL)): InternalRaisesFuture[T,
    (ACMEError, CancelledError)] {.stackTrace: false, ...raises: [], gcsafe,
                                   raises: [], raises: [].}