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diff --git a/lib/pleroma/upload/filter.ex b/lib/pleroma/upload/filter.ex
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+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2022 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Upload.Filter do
+  @moduledoc """
+  Upload Filter behaviour
+
+  This behaviour allows to run filtering actions just before a file is uploaded. This allows to:
+
+  * morph in place the temporary file
+  * change any field of a `Pleroma.Upload` struct
+  * cancel/stop the upload
+  """
+
+  require Logger
+
+  @callback filter(upload :: struct()) ::
+              {:ok, :filtered}
+              | {:ok, :noop}
+              | {:ok, :filtered, upload :: struct()}
+              | {:error, any()}
+
+  @spec filter([module()], upload :: struct()) :: {:ok, upload :: struct()} | {:error, any()}
+
+  def filter([], upload) do
+    {:ok, upload}
+  end
+
+  def filter([filter | rest], upload) do
+    case filter.filter(upload) do
+      {:ok, :filtered} ->
+        filter(rest, upload)
+
+      {:ok, :filtered, upload} ->
+        filter(rest, upload)
+
+      {:ok, :noop} ->
+        filter(rest, upload)
+
+      error ->
+        Logger.error("#{__MODULE__}: Filter #{filter} failed: #{inspect(error)}")
+        error
+    end
+  end
+end