clacks/lib/clacks_web/controllers/outbox_controller.ex

defmodule ClacksWeb.OutboxController do
  use ClacksWeb, :controller
  alias Clacks.{Actor, Timeline}

  @context "https://www.w3.org/ns/activitystreams"

  plug :get_actor

  defp get_actor(%Plug.Conn{path_params: %{"username" => username}} = conn, _opts) do
    case Actor.get_by_nickname(username) do
      %Actor{local: true} = actor ->
        assign(conn, :actor, actor)

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

  def outbox(conn, %{} = params) do
    actor = conn.assigns[:actor]

    activities = Timeline.actor_timeline(actor, params, true)

    data = %{
      "@context" => @context,
      "type" => "OrderedCollection",
      "id" => current_url(conn, %{}),
      "first" => outbox_page(conn, params, activities)
    }

    conn
    |> put_resp_header("content-type", "application/activity+json")
    |> json(data)
  end

  def outbox(conn, params) do
    actor = conn.assigns[:actor]

    activities = Timeline.actor_timeline(actor, params, true)

    data =
      outbox_page(conn, params, activities)
      |> Map.put("@context", @context)

    conn
    |> put_resp_header("content-type", "application/activity+json")
    |> json(data)
  end

  defp outbox_page(conn, pagination_params, activities) do
    last_id = List.last(activities).id

    %{
      "type" => "OrderedColletionPage",
      "partOf" => current_url(conn, %{}),
      "id" => current_url(conn, pagination_params),
      "next" => current_url(conn, %{max_id: last_id}),
      "orderedItems" => Enum.map(activities, & &1.data)
    }
  end
end