JSON Serialization of Elixir 2-ples

extend_jsx_encoder.ex

defimpl JSX.Encoder, for: Tuple do
  def json({__t1, __t2}) when is_list(i1) do
    [:start_object, "__t1", __t1, "__t2", JSX.encode!(__t2), :end_object]
  end
  def json({__t1, __t2}) do
    [:start_object, "__t1", __t2, "tuple_list", __t2, :end_object]
  end
end

serialize_2ples.ex

# JSON does not allow tuples.
# We have 2-ples, so we encode them as maps
# with conventional keys: __t1 and __t2
defp tuples_to_maps([]) do
  []
end
defp tuples_to_maps([first | rest]) do
  [tuples_to_maps(first)] ++ tuples_to_maps(rest)
end
defp tuples_to_maps(%{} = map) do
  Enum.reduce(map, %{}, fn ({k, v}, acc) ->
    Map.put(acc, k, tuples_to_maps(v))
  end)
end
defp tuples_to_maps({i1, i2}) do
  %{"__t1" => i1, "__t2" => tuples_to_maps(i2)}
end
defp tuples_to_maps(e) do
  e
end

defp maps_to_tuples([]) do
  []
end
defp maps_to_tuples([first | rest]) do
  [maps_to_tuples(first)] ++ maps_to_tuples(rest)
end
defp maps_to_tuples(%{"__t1" => i1, "__t2" => i2}) do
  {i1, maps_to_tuples(i2)}
end
defp maps_to_tuples(%{} = map) do
  Enum.reduce(map, %{}, fn ({k, v}, acc) ->
    Map.put(acc, k, maps_to_tuples(v))
  end)
end
defp maps_to_tuples(e) do
  e
end