defmodule ToweropsWeb.RemoteIp do
  @moduledoc """
  Shared helpers for extracting and formatting remote IP addresses.
  """

  import Plug.Conn, only: [get_req_header: 2]

  @spec from_conn(Plug.Conn.t()) :: String.t() | nil
  def from_conn(conn) do
    case get_req_header(conn, "x-forwarded-for") do
      [forwarded | _] ->
        forwarded
        |> String.split(",")
        |> List.first()
        |> String.trim()

      [] ->
        from_x_real_ip_or_tuple(conn)
    end
  end

  @spec from_socket(Phoenix.Socket.t()) :: String.t() | nil
  def from_socket(socket) do
    case socket.transport_pid do
      nil ->
        nil

      pid when is_pid(pid) ->
        case :ranch.get_addr(pid) do
          {ip, _port} when is_tuple(ip) -> format(ip)
          _ -> nil
        end
    end
  rescue
    _ -> nil
  end

  @spec format(tuple() | nil) :: String.t() | nil
  def format({a, b, c, d}), do: "#{a}.#{b}.#{c}.#{d}"

  def format({a, b, c, d, e, f, g, h}) do
    Enum.map_join([a, b, c, d, e, f, g, h], ":", &(&1 |> Integer.to_string(16) |> String.upcase()))
  end

  def format(_), do: nil

  defp from_x_real_ip_or_tuple(conn) do
    case get_req_header(conn, "x-real-ip") do
      [real_ip | _] -> real_ip
      [] -> format(conn.remote_ip)
    end
  end
end