replace_map_values.ex

defmodule ReplaceMapValues do
  def call(obj, opts = [replace_fn: _]), do: iterate(obj, opts)

  defp iterate(maybe_struct = %{}, opts = [replace_fn: func]) do
    enumerable =
      case maybe_struct do
        struct = %_{} -> Map.from_struct(struct)
        map = %{} -> map
      end

    # Preserve the original structure, but must iterate over it as a map due to Enumerable
    new_value =
      Enum.reduce(enumerable, maybe_struct, fn {k, v}, acc ->
        Map.put(acc, k, iterate(v, opts))
      end)

    func.(new_value)
  end

  defp iterate([head | rest], opts) do
    [iterate(head, opts) | iterate(rest, opts)]
  end

  defp iterate(primitive, replace_fn: func) do
    func.(primitive)
  end
end