clacks/lib/clacks_web/controllers/activities_controller.ex

defmodule ClacksWeb.ActivitiesController do
  use ClacksWeb, :controller
  alias Clacks.{ActivityPub, Activity}
  alias ClacksWeb.Router.Helpers, as: Routes
  alias ClacksWeb.Endpoint

  def get(conn, _params) do
    ap_id = current_url(conn, %{})

    case Activity.get_by_ap_id(ap_id) do
      %Activity{local: true, id: id, data: data} ->
        case conn.assigns[:format] do
          "activity+json" ->
            json(conn, data)

          "html" ->
            redirect(conn, to: Routes.frontend_path(Endpoint, :status, id))
        end

      _ ->
        case conn.assigns[:format] do
          "activity+json" ->
            conn
            |> put_status(404)
            |> json(%{error: "Not Found"})

          "html" ->
            resp(conn, 404, "Not Found")
        end
    end
  end

  def get_status(conn, %{"id" => status_id}) do
    case Activity.get(status_id) do
      %Activity{local: true, data: data} ->
        json(conn, data)

      _ ->
        conn
        |> put_status(404)
        |> json(%{error: "Not Found"})
    end
  end
end