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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.EnsureRePrepended do
   6   alias Pleroma.Object
   7
   8   @moduledoc "Ensure a re: is prepended on replies to a post with a Subject"
   9   @behaviour Pleroma.Web.ActivityPub.MRF.Policy
  10
  11   @reply_prefix Regex.compile!("^re:[[:space:]]*", [:caseless])
  12
  13   def history_awareness, do: :auto
  14
  15   def filter_by_summary(
  16         %{data: %{"summary" => parent_summary}} = _in_reply_to,
  17         %{"summary" => child_summary} = child
  18       )
  19       when not is_nil(child_summary) and byte_size(child_summary) > 0 and
  20              not is_nil(parent_summary) and byte_size(parent_summary) > 0 do
  21     if (child_summary == parent_summary and not Regex.match?(@reply_prefix, child_summary)) or
  22          (Regex.match?(@reply_prefix, parent_summary) &&
  23             Regex.replace(@reply_prefix, parent_summary, "") == child_summary) do
  24       Map.put(child, "summary", "re: " <> child_summary)
  25     else
  26       child
  27     end
  28   end
  29
  30   def filter_by_summary(_in_reply_to, child), do: child
  31
  32   def filter(%{"type" => type, "object" => child_object} = object)
  33       when type in ["Create", "Update"] and is_map(child_object) do
  34     child =
  35       child_object["inReplyTo"]
  36       |> Object.normalize(fetch: false)
  37       |> filter_by_summary(child_object)
  38
  39     object = Map.put(object, "object", child)
  40
  41     {:ok, object}
  42   end
  43
  44   def filter(object), do: {:ok, object}
  45
  46   def describe, do: {:ok, %{}}
  47 end