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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Web.ActivityPub.MRF.HellthreadPolicy do
   6   alias Pleroma.User
   7   @behaviour Pleroma.Web.ActivityPub.MRF
   8
   9   defp delist_message(message) do
  10     delist_threshold = Pleroma.Config.get([:mrf_hellthread, :delist_threshold])
  11     follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
  12
  13     message =
  14       with {:public, recipients} <- get_recipient_count(message) do
  15         if recipients > delist_threshold and delist_threshold > 0 do
  16           message
  17           |> Map.put("to", [follower_collection])
  18           |> Map.put("cc", ["https://www.w3.org/ns/activitystreams#Public"])
  19         else
  20           message
  21         end
  22       else
  23         _ -> message
  24       end
  25
  26     {:ok, message}
  27   end
  28
  29   defp reject_message(message) do
  30     reject_threshold =
  31       Pleroma.Config.get(
  32         [:mrf_hellthread, :reject_threshold],
  33         Pleroma.Config.get([:mrf_hellthread, :threshold])
  34       )
  35
  36     with {_, recipients} <- get_recipient_count(message) do
  37       if recipients > reject_threshold and reject_threshold > 0 do
  38         {:reject, nil}
  39       else
  40         {:ok, message}
  41       end
  42     end
  43   end
  44
  45   defp get_recipient_count(message) do
  46     recipients = (message["to"] || []) ++ (message["cc"] || [])
  47     follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
  48
  49     if Enum.member?(recipients, "https://www.w3.org/ns/activitystreams#Public") do
  50       recipients
  51       |> List.delete("https://www.w3.org/ns/activitystreams#Public")
  52       |> List.delete(follower_collection)
  53
  54       {:public, length(recipients)}
  55     else
  56       recipients
  57       |> List.delete(follower_collection)
  58
  59       {:not_public, length(recipients)}
  60     end
  61   end
  62
  63   @impl true
  64   def filter(%{"type" => "Create"} = message) do
  65     with {:ok, message} <- reject_message(message),
  66          {:ok, message} <- delist_message(message) do
  67       {:ok, message}
  68     else
  69       _e -> {:reject, nil}
  70     end
  71   end
  72
  73   @impl true
  74   def filter(message), do: {:ok, message}
  75 end