anchor.diff:      , callback         = CallbackOpt
       }
   ) ->
  -    % TODO: Encoding
       URI           = ?resource:get_uri(Resource),
       BaseStringURI = ?signature_base_string_uri:cons(URI),
       TokenPair =
  
positive.code:         ++ TokenPair
          ++ VerifierPair
          ++ CallbackPair,
      ParameterSortComparator =
          fun ({K , V1}, {K , V2}) -> V1 =< V2
          ;   ({K1,  _}, {K2,  _}) -> K1 =< K2
          end,
      ParameterPairsSorted = lists:sort(ParameterSortComparator, ParameterPairs),
      ParameterAppend =
          fun ({K, V}, Acc) ->
              <<Acc/binary, K/binary, "=", V/binary>>
  
negative.code:     , ?AMPERSAND
      ,  ParametersString/binary
      >>.
  
  
  -spec encode(binary()) ->
      binary().
  encode(<<String/binary>>) ->
      cow_qs:urlencode(String).
  
  
  %% 3.4.1.  Signature Base String
  