# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.Workers.AttachmentsCleanupWorker do
  import Ecto.Query

  alias Pleroma.Object
  alias Pleroma.Repo

  use Pleroma.Workers.WorkerHelper, queue: "attachments_cleanup"

  @impl Oban.Worker
  def perform(
        %{
          "op" => "cleanup_attachments",
          "object" => %{"data" => %{"attachment" => [_ | _] = attachments, "actor" => actor}}
        },
        _job
      ) do
    hrefs =
      Enum.flat_map(attachments, fn attachment ->
        Enum.map(attachment["url"], & &1["href"])
      end)

    names = Enum.map(attachments, & &1["name"])

    uploader = Pleroma.Config.get([Pleroma.Upload, :uploader])

    prefix =
      case Pleroma.Config.get([Pleroma.Upload, :base_url]) do
        nil -> "media"
        _ -> ""
      end

    base_url =
      String.trim_trailing(
        Pleroma.Config.get([Pleroma.Upload, :base_url], Pleroma.Web.base_url()),
        "/"
      )

    # find all objects for copies of the attachments, name and actor doesn't matter here
    object_ids_and_hrefs =
      from(o in Object,
        where:
          fragment(
            "to_jsonb(array(select jsonb_array_elements((?)#>'{url}') ->> 'href' where jsonb_typeof((?)#>'{url}') = 'array'))::jsonb \\?| (?)",
            o.data,
            o.data,
            ^hrefs
          )
      )
      # The query above can be time consumptive on large instances until we
      # refactor how uploads are stored
      |> Repo.all(timeout: :infinity)
      # we should delete 1 object for any given attachment, but don't delete
      # files if there are more than 1 object for it
      |> Enum.reduce(%{}, fn %{
                               id: id,
                               data: %{
                                 "url" => [%{"href" => href}],
                                 "actor" => obj_actor,
                                 "name" => name
                               }
                             },
                             acc ->
        Map.update(acc, href, %{id: id, count: 1}, fn val ->
          case obj_actor == actor and name in names do
            true ->
              # set id of the actor's object that will be deleted
              %{val | id: id, count: val.count + 1}

            false ->
              # another actor's object, just increase count to not delete file
              %{val | count: val.count + 1}
          end
        end)
      end)
      |> Enum.map(fn {href, %{id: id, count: count}} ->
        # only delete files that have single instance
        with 1 <- count do
          href
          |> String.trim_leading("#{base_url}/#{prefix}")
          |> uploader.delete_file()

          {id, href}
        else
          _ -> {id, nil}
        end
      end)

    object_ids = Enum.map(object_ids_and_hrefs, fn {id, _} -> id end)

    from(o in Object, where: o.id in ^object_ids)
    |> Repo.delete_all()

    object_ids_and_hrefs
    |> Enum.filter(fn {_, href} -> not is_nil(href) end)
    |> Enum.map(&elem(&1, 1))
    |> Pleroma.Web.MediaProxy.Invalidation.purge()

    {:ok, :success}
  end

  def perform(%{"op" => "cleanup_attachments", "object" => _object}, _job), do: {:ok, :skip}
end