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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.Upload.Filter do
   6   @moduledoc """
   7   Upload Filter behaviour
   8
   9   This behaviour allows to run filtering actions just before a file is uploaded. This allows to:
  10
  11   * morph in place the temporary file
  12   * change any field of a `Pleroma.Upload` struct
  13   * cancel/stop the upload
  14   """
  15
  16   require Logger
  17
  18   @callback filter(upload :: struct()) ::
  19               {:ok, :filtered}
  20               | {:ok, :noop}
  21               | {:ok, :filtered, upload :: struct()}
  22               | {:error, any()}
  23
  24   @spec filter([module()], upload :: struct()) :: {:ok, upload :: struct()} | {:error, any()}
  25
  26   def filter([], upload) do
  27     {:ok, upload}
  28   end
  29
  30   def filter([filter | rest], upload) do
  31     case filter.filter(upload) do
  32       {:ok, :filtered} ->
  33         filter(rest, upload)
  34
  35       {:ok, :filtered, upload} ->
  36         filter(rest, upload)
  37
  38       {:ok, :noop} ->
  39         filter(rest, upload)
  40
  41       error ->
  42         Logger.error("#{__MODULE__}: Filter #{filter} failed: #{inspect(error)}")
  43         error
  44     end
  45   end
  46 end