defmodule PhoenixKitWeb.Users.QrLoginComplete do
  @moduledoc """
  Completion endpoint for QR device-handoff login.

  The desktop LiveView navigates here once its request is approved on the
  phone, carrying the one-time login token. This controller exchanges that
  token for the approved user's uuid (exactly once, via
  `PhoenixKit.Users.QrLogin.consume/1`) and establishes the session with
  PhoenixKit's own login machinery.

  Keyfob's login token is single-use and short-lived, so a replayed or
  stale URL lands on the login page rather than signing anyone in.
  """
  use PhoenixKitWeb, :controller

  alias PhoenixKit.Users.Auth, as: Users
  alias PhoenixKit.Users.QrLogin, as: QrLoginContext
  alias PhoenixKit.Utils.Routes
  alias PhoenixKitWeb.Users.Auth, as: UserAuth

  def complete(conn, %{"token" => token}) do
    with true <- QrLoginContext.enabled?(),
         {:ok, user_uuid} <- QrLoginContext.consume(token),
         %{} = user <- Users.get_user(user_uuid) do
      conn
      |> put_flash(:info, gettext("Signed in with QR code."))
      |> UserAuth.log_in_user(user)
    else
      _ ->
        conn
        |> put_flash(:error, gettext("This QR sign-in link is invalid or has expired."))
        |> redirect(to: Routes.path("/users/log-in"))
    end
  end

  def complete(conn, _params) do
    conn
    |> put_flash(:error, gettext("This QR sign-in link is invalid or has expired."))
    |> redirect(to: Routes.path("/users/log-in"))
  end
end