defmodule Pathex.Builder.MatchableViewer do
  # Viewer-builder which creates function which matches with one big case
  @moduledoc false

  alias Pathex.Common
  import Pathex.Builder.Viewer
  @behaviour Pathex.Builder

  @structure_variable {:x, [], Elixir}
  @function_variable {:function, [], Elixir}

  def build(combination) do
    getters =
      combination
      |> Pathex.Combination.to_paths()
      |> Enum.flat_map(&path_to_getter(&1))

    (getters ++ fallback())
    |> Common.to_case()
    |> Pathex.Builder.Code.new_arg_pipe([@structure_variable, @function_variable])
  end

  defp path_to_getter(path) do
    x = {:x, [], Elixir}
    {:ok, match} = match_from_path(path, x)

    quote do
      unquote(match) -> unquote(@function_variable).(unquote(x))
    end
  end
end