defmodule Zig.Typespec do
  @moduledoc """
  handles creating typespecs for zig Nif functions
  """

  alias Zig.Parser.Nif

  @type_for %{
    "void"         => nil,
    "u8"           => quote [context: Elixir] do 0..255 end,
    "u16"          => quote [context: Elixir] do 0..0xFFFF end,
    "u32"          => quote [context: Elixir] do 0..0xFFFF_FFFF end,
    "u64"          => quote [context: Elixir] do non_neg_integer end,
    "i32"          => quote [context: Elixir] do (-2_147_483_648)..2_147_483_647 end,
    "i64"          => quote [context: Elixir] do integer end,
    "c_uint"       => quote [context: Elixir] do non_neg_integer end,
    "c_int"        => quote [context: Elixir] do integer end,
    "c_ulong"      => quote [context: Elixir] do non_neg_integer end,
    "c_long"       => quote [context: Elixir] do integer end,
    "usize"        => quote [context: Elixir] do non_neg_integer end,
    "isize"        => quote [context: Elixir] do integer end,
    "f16"          => quote [context: Elixir] do float end,
    "f32"          => quote [context: Elixir] do float end,
    "f64"          => quote [context: Elixir] do float end,
    "bool"         => quote [context: Elixir] do boolean end,
    "beam.term"    => quote [context: Elixir] do term end,
    "e.ErlNifTerm" => quote [context: Elixir] do term end,
    "beam.pid"     => quote [context: Elixir] do pid end,
    "e.ErlNifPid"  => quote [context: Elixir] do pid end,
    "beam.atom"    => quote [context: Elixir] do atom end,
    "[]u8"         => quote [context: Elixir] do binary end
  }

  @doc false
  def from_nif(nif = %Nif{}) do
    {nif.name, nif.arity}
    argument_types = Enum.flat_map(nif.args, fn
      "beam.env" -> []
      "?*e.ErlNifEnv" -> []
      arg ->
        [type_for(arg)]
    end)

    return_type = type_for(nif.retval)

    {:@, [context: Elixir, import: Kernel],
      [{:spec, [context: Elixir],
        [{:"::", [],
          [
            {nif.name, [], argument_types},
            return_type
          ]}]}]}
  end

  defp type_for("[]u8"), do: @type_for["[]u8"]
  defp type_for("[]" <> type), do: [type_for(type)]
  defp type_for(type) do @type_for[type] end

end