ex_rlp

defmodule ExRLP.Decode.Result do
  @moduledoc false

  defstruct acc: nil, result: nil

  def add_item(result = %__MODULE__{acc: nil}, item) do
    new_acc = item

    %{result | acc: new_acc}
  end

  def add_item(result = %__MODULE__{acc: acc}, item) when is_list(acc) do
    new_acc = [item | result.acc]

    %{result | acc: new_acc}
  end

  def add_item(result = %__MODULE__{acc: acc}, item) do
    new_acc = [item, acc]

    %{result | acc: new_acc}
  end

  def add_result_item(result_struct = %__MODULE__{result: nil}, item) do
    new_result = item

    %{result_struct | result: new_result}
  end

  def add_result_item(result_struct = %__MODULE__{result: result}, item) when is_list(result) do
    new_result = [item | result]

    %{result_struct | result: new_result}
  end

  def add_result_item(result_struct = %__MODULE__{result: result}, item) do
    new_result = [item, result]

    %{result_struct | result: new_result}
  end

  def reverse(result = %__MODULE__{result: nil}) do
    new_result = reverse_acc(result.acc)

    %{result | acc: [], result: new_result}
  end

  def reverse(result) do
    reversed_acc = reverse_acc(result.acc)

    new_result =
      cond do
        is_nil(result.result) ->
          reversed_acc

        is_nil(reversed_acc) ->
          result.result

        is_list(result.result) && is_list(reversed_acc) ->
          result.result ++ reversed_acc

        is_list(result.result) ->
          result.result ++ [reversed_acc]

        is_list(reversed_acc) ->
          [result] ++ reversed_acc
      end

    %{result | acc: [], result: new_result}
  end

  defp reverse_acc(acc) when is_list(acc) do
    Enum.reverse(acc)
  end

  defp reverse_acc(acc), do: acc
end