exalign

defmodule Example.CaseArms do
  def classify(result) do
    case result do
      {:ok, value}     -> value
      {:error, reason} -> {:error, reason}
      _                -> nil
    end
  end

  def classify_tuple({a, b}) do
    case {a, b} do
      {nil, nil}                    -> :both_nil
      {x,   nil} when is_integer(x) -> {:left, x}
      {nil, y}                      -> {:right, y}
      {x,   y}                      -> {x, y}
    end
  end

  def pipe_case(list) do
    list
    |> Enum.filter(&is_integer/1)
    |> case do
      []       -> :empty
      int_list -> int_list
    end
  end

  def more_complex_case(text, components) do
    components
    |> Enum.reduce_while(%{}, fn component, acc ->
      component_text = maybe_preprocess(text, component.__preprocess__())

      case component.__fields__()
        |> Enum.map(fn {name, field} -> {name, Field.extract(field, component_text)} end)
        |> Enum.reject(fn {_k, v}    -> is_nil(v) end)
        |> Enum.into(%{})
        |> maybe_postprocess(component)
      do
        {:error, _} = err -> {:halt, err}
        fields            -> {:cont, Map.merge(acc, fields)}
      end
    end)
  end
end