defmodule WaspVM.Decoder.FunctionSectionParser do
  alias WaspVM.LEB128

  @moduledoc false

  def parse(section) do
    indexes = if section !== nil, do: parse_type_entry(section), else: []

    {:function_types, Enum.reverse(indexes)}
  end

  @spec parse_type_entry(Binary) :: List
  defp parse_type_entry(entry) do
    {count, entry} = LEB128.decode_unsigned(entry)
    parse_type_entry(:indexing, [], count, entry)
  end

  defp parse_type_entry(:indexing, v, _n, ""), do: v
  defp parse_type_entry(:indexing, v, n, entry) do
    {id, rem} = LEB128.decode_unsigned(entry)
  	parse_type_entry(:indexing, [id | v], n - 1, rem)
  end
end