httparrot

defmodule HTTParrot.IPHandler do
  @moduledoc """
  Returns Origin IP
  """
  use HTTParrot.Cowboy, methods: ~w(GET HEAD OPTIONS)

  def content_types_provided(req, state) do
    {[{{"application", "json", []}, :get_json}], req, state}
  end

  def get_json(req, state) do
    {ip, _port} = :cowboy_req.peer(req)
    forwarded_for = :cowboy_req.parse_header("x-forwarded-for", req)

    case forwarded_for do
      :undefined ->
        {response(ip), req, state}

      _ ->
        {response(to_tuple(forwarded_for)), req, state}
    end
  end

  defp to_tuple(client_ip) do
    client_ip
    |> hd
    |> String.split(".")
    |> Enum.map(fn x -> String.to_integer(x) end)
    |> List.to_tuple()
  end

  defp response({127, 0, 0, 1}) do
    [origin: ""] |> JSX.encode!()
  end

  defp response(ip) do
    ip = :inet_parse.ntoa(ip) |> to_string
    [origin: ip] |> JSX.encode!()
  end
end