anchor.diff:  init(Req, State) ->
       City   = city_to_module(cowboy_req:binding(city, Req)),
       Method = cowboy_req:binding(method, Req),
  -    Params = case cowboy_req:qs(Req) of
  -        <<>> -> undefined;
  -        Val  -> qsp:decode(Val)
  +    Params = case params(Req) of
  +        undefined -> undefined;
  +        Val       -> qsp:decode(Val)
       end,
   
       {Status, Data} = handle(City, Method, Params),
  
positive.code: %% Helpers
  %%
  
  json_error(Msg) ->
      [{<<"error">>, Msg}].
  
  
negative.code:     {404, json_error(<<"city_not_found">>)};
  handle(City, undefined, _) ->
      {200, transee_worker:transports(City)};
  handle(City, <<"positions">>, #{<<"type">> := T, <<"numbers">> := N}) when is_list(T), is_map(N) ->
      Result = lists:foldl(fun(Type, Acc) ->
          case maps:get(Type, N, undefined) of
              undefined -> Acc;
              Numbers   -> [transee_worker:positions(City, Type, Numbers)|Acc]
          end
      end, [], T),
      {200, Result};
  handle(City, <<"positions">>, #{<<"type">> := T}) when is_list(T) ->
      Result = lists:map(fun(Type) ->
          transee_worker:positions(City, Type)
      end, T),
      {200, Result};
  handle(City, <<"positions">>, #{<<"type">> := T, <<"numbers">> := N}) when is_list(N) ->
      {200, transee_worker:positions(City, T, N)};
  handle(City, <<"positions">>, #{<<"type">> := T}) ->
  