type auth_mechanism = PLAIN  [@@deriving show { with_path = false }]

type sasl_error =
  | NotAuthorized

let read_sasl_error = function
  | "not-authorized" -> NotAuthorized
  | _ -> failwith "Unsupported SASL error returned by the server."

let send_auth_stanza (stream, push) jid pass mechanism =
  let gen_auth = function
    | PLAIN -> Base64.encode_exn ("\x00" ^ jid ^ "\x00" ^ pass)
  in let xmlns = "urn:ietf:params:xml:ns:xmpp-sasl" in
     let stanza_list = [`Start_element
                          ((xmlns, "auth"),
                           [(("", "xmlns"), xmlns);
                            (("", "mechanism"), show_auth_mechanism mechanism)]);
                        `Text [gen_auth mechanism];
                        `End_element]
     in Markup.(stanza_list |> of_list |> write_xml |> to_string) |> Option.some |> push;
        (* TODO: use stream result for exceptions, etc. *)
        Lwt_stream.get stream