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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, threshold) when threshold > 0 do
  10     follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
  11
  12     follower_collection? = Enum.member?(message["to"] ++ message["cc"], follower_collection)
  13
  14     message =
  15       case get_recipient_count(message) do
  16         {:public, recipients}
  17         when follower_collection? and recipients > threshold ->
  18           message
  19           |> Map.put("to", [follower_collection])
  20           |> Map.put("cc", ["https://www.w3.org/ns/activitystreams#Public"])
  21
  22         {:public, recipients} when recipients > threshold ->
  23           message
  24           |> Map.put("to", [])
  25           |> Map.put("cc", ["https://www.w3.org/ns/activitystreams#Public"])
  26
  27         _ ->
  28           message
  29       end
  30
  31     {:ok, message}
  32   end
  33
  34   defp delist_message(message, _threshold), do: {:ok, message}
  35
  36   defp reject_message(message, threshold) when threshold > 0 do
  37     with {_, recipients} <- get_recipient_count(message) do
  38       if recipients > threshold do
  39         {:reject, nil}
  40       else
  41         {:ok, message}
  42       end
  43     end
  44   end
  45
  46   defp reject_message(message, _threshold), do: {:ok, message}
  47
  48   defp get_recipient_count(message) do
  49     recipients = (message["to"] || []) ++ (message["cc"] || [])
  50     follower_collection = User.get_cached_by_ap_id(message["actor"]).follower_address
  51
  52     if Enum.member?(recipients, "https://www.w3.org/ns/activitystreams#Public") do
  53       recipients =
  54         recipients
  55         |> List.delete("https://www.w3.org/ns/activitystreams#Public")
  56         |> List.delete(follower_collection)
  57
  58       {:public, length(recipients)}
  59     else
  60       recipients =
  61         recipients
  62         |> List.delete(follower_collection)
  63
  64       {:not_public, length(recipients)}
  65     end
  66   end
  67
  68   @impl true
  69   def filter(%{"type" => "Create"} = message) do
  70     reject_threshold =
  71       Pleroma.Config.get(
  72         [:mrf_hellthread, :reject_threshold],
  73         Pleroma.Config.get([:mrf_hellthread, :threshold])
  74       )
  75
  76     delist_threshold = Pleroma.Config.get([:mrf_hellthread, :delist_threshold])
  77
  78     with {:ok, message} <- reject_message(message, reject_threshold),
  79          {:ok, message} <- delist_message(message, delist_threshold) do
  80       {:ok, message}
  81     else
  82       _e -> {:reject, nil}
  83     end
  84   end
  85
  86   @impl true
  87   def filter(message), do: {:ok, message}
  88 end