postland/lib/postland/follows.ex

defmodule Postland.Follows do
  use Phoenix.VerifiedRoutes, endpoint: PostlandWeb.Endpoint, router: PostlandWeb.Router

  import Ecto.Query, warn: false

  alias Postland.Accounts
  alias Postland.Activity
  alias Postland.Follow
  alias Postland.Repo
  alias ActivityPub.Headers

  alias Ecto.Multi

  def all_following() do
    my_actor_id = Postland.my_actor_id()

    from(f in Follow, where: f.follower == ^my_actor_id, where: not is_nil(f.confirmed_at))
    |> Repo.all()
  end

  def all_followers() do
    my_actor_id = Postland.my_actor_id()

    from(f in Follow, where: f.followee == ^my_actor_id, where: not is_nil(f.confirmed_at))
    |> Repo.all()
  end

  def record_and_send_acceptance(request) do
    Multi.new()
    |> Multi.run(:confirm_timestamp, fn _data, _repo -> confirm_request(request) end)
    |> Multi.run(:send_acceptance, fn _data, _repo ->
      send_acceptance(request)
    end)
    |> Repo.transaction()
  end

  def send_acceptance(request) do
    {:ok, actor} = ActivityPub.fetch_actor(request.follower)
    inbox = Map.get(actor, "inbox")

    case get_follow_activity(request.follower) do
      nil ->
        {:error, "could not find Follow activity to Accept"}

      follow_activity ->
        body =
          %{
            "@context" => "https://www.w3.org/ns/activitystreams",
            "type" => "Accept",
            "actor" => Postland.my_actor_id(),
            "object" => %{
              "actor" => request.follower,
              "id" => Map.get(follow_activity.data, "id"),
              "object" => Postland.my_actor_id(),
              "type" => "Follow"
            }
          }
          |> Jason.encode!()

        headers =
          Headers.signing_headers(
            "POST",
            inbox,
            body,
            Postland.my_actor_id(),
            Accounts.solo_user().private_key
          )

        Req.post(inbox, headers: headers, body: body)
    end
  end

  def get_follow_activity(follower) do
    from(a in Activity,
      where: a.type == "Follow",
      where: a.actor_id == ^follower,
      limit: 1,
      order_by: [desc: :inserted_at]
    )
    |> Repo.one()
  end

  def record_and_send_follow_request(to_actor_id) do
    Multi.new()
    |> Multi.run(:follow_record, fn _data, _repo -> record_outbound_request(to_actor_id) end)
    |> Multi.run(:send_request, fn _data, _repo ->
      send_follow_request(to_actor_id)
    end)
    |> Repo.transaction()
    |> case do
      {:ok, %{follow_record: follow_record}} = result ->
        Phoenix.PubSub.broadcast(
          Postland.PubSub,
          "follows:#{to_actor_id}",
          {:update, follow_record}
        )

        result

      other ->
        other
    end
  end

  def send_follow_request(to_actor_id) do
    encoded_followee = Base.url_encode64(to_actor_id, padding: false)
    encoded_follower = Base.url_encode64(Postland.my_actor_id(), padding: false)

    {:ok, actor} = ActivityPub.fetch_actor(to_actor_id)
    inbox = Map.get(actor, "inbox")

    follow_request =
      %{
        "@context" => "https://www.w3.org/ns/activitystreams",
        "id" => url(~p"/follows/#{encoded_followee}/#{encoded_follower}"),
        "type" => "Follow",
        "actor" => Postland.my_actor_id(),
        "object" => to_actor_id
      }
      |> Jason.encode!()

    headers =
      Headers.signing_headers(
        "POST",
        inbox,
        follow_request,
        Postland.my_actor_id(),
        Accounts.solo_user().private_key
      )

    Req.post(inbox, headers: headers, body: follow_request)
  end

  def get(follower, followee) do
    from(f in Follow, where: f.followee == ^followee, where: f.follower == ^follower)
    |> Repo.one()
  end

  def pending_inbound_requests() do
    my_actor_id = Postland.my_actor_id()

    from(f in Follow, where: f.followee == ^my_actor_id, where: is_nil(f.confirmed_at))
    |> Repo.all()
  end

  def record_outbound_request(to_actor_id) do
    Postland.my_actor_id()
    |> Follow.changeset(to_actor_id)
    |> Repo.insert(conflict_target: [:followee, :follower], on_conflict: :nothing)
  end

  def record_inbound_request(from_actor_id) do
    from_actor_id
    |> Follow.changeset(Postland.my_actor_id())
    |> Repo.insert(conflict_target: [:followee, :follower], on_conflict: :nothing)
  end

  def confirm_request(request) do
    request
    |> Follow.confirm_changeset()
    |> Repo.update()
    |> case do
      {:ok, follow} ->
        Phoenix.PubSub.broadcast(Postland.PubSub, "follows:#{follow.followee}", {:update, follow})
    end
  end
end