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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Upload.Filter.AnonymizeFilename do
   6   @moduledoc """
   7   Replaces the original filename with a pre-defined text or randomly generated string.
   8
   9   Should be used after `Pleroma.Upload.Filter.Dedupe`.
  10   """
  11   @behaviour Pleroma.Upload.Filter
  12
  13   alias Pleroma.Config
  14   alias Pleroma.Upload
  15
  16   def filter(%Upload{name: name} = upload) do
  17     extension = List.last(String.split(name, "."))
  18     name = predefined_name(extension) || random(extension)
  19     {:ok, :filtered, %Upload{upload | name: name}}
  20   end
  21
  22   def filter(_), do: {:ok, :noop}
  23
  24   @spec predefined_name(String.t()) :: String.t() | nil
  25   defp predefined_name(extension) do
  26     with name when not is_nil(name) <- Config.get([__MODULE__, :text]),
  27          do: String.replace(name, "{extension}", extension)
  28   end
  29
  30   defp random(extension) do
  31     string =
  32       10
  33       |> :crypto.strong_rand_bytes()
  34       |> Base.url_encode64(padding: false)
  35
  36     string <> "." <> extension
  37   end
  38 end