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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Web.ActivityPub.MRF.AntiLinkSpamPolicy do
   6   alias Pleroma.User
   7
   8   @behaviour Pleroma.Web.ActivityPub.MRF.Policy
   9
  10   require Logger
  11
  12   @impl true
  13   def history_awareness, do: :auto
  14
  15   # has the user successfully posted before?
  16   defp old_user?(%User{} = u) do
  17     u.note_count > 0 || u.follower_count > 0
  18   end
  19
  20   # does the post contain links?
  21   defp contains_links?(%{"content" => content} = _object) do
  22     content
  23     |> Floki.parse_fragment!()
  24     |> Floki.filter_out("a.mention,a.hashtag,a[rel~=\"tag\"],a.zrl")
  25     |> Floki.attribute("a", "href")
  26     |> length() > 0
  27   end
  28
  29   defp contains_links?(_), do: false
  30
  31   @impl true
  32   def filter(%{"type" => "Create", "actor" => actor, "object" => object} = message) do
  33     with {:ok, %User{local: false} = u} <- User.get_or_fetch_by_ap_id(actor),
  34          {:contains_links, true} <- {:contains_links, contains_links?(object)},
  35          {:old_user, true} <- {:old_user, old_user?(u)} do
  36       {:ok, message}
  37     else
  38       {:ok, %User{local: true}} ->
  39         {:ok, message}
  40
  41       {:contains_links, false} ->
  42         {:ok, message}
  43
  44       {:old_user, false} ->
  45         {:reject, "[AntiLinkSpamPolicy] User has no posts nor followers"}
  46
  47       {:error, _} ->
  48         {:reject, "[AntiLinkSpamPolicy] Failed to get or fetch user by ap_id"}
  49
  50       e ->
  51         {:reject, "[AntiLinkSpamPolicy] Unhandled error #{inspect(e)}"}
  52     end
  53   end
  54
  55   # in all other cases, pass through
  56   def filter(message), do: {:ok, message}
  57
  58   @impl true
  59   def describe, do: {:ok, %{}}
  60 end