defmodule Pleroma.Workers.PurgeExpiredActivity do
  @moduledoc """
  Worker which purges expired activity.
  """

  use Oban.Worker, queue: :activity_expiration, max_attempts: 1

  import Ecto.Query

  def enqueue(args) do
    with true <- enabled?(),
         args when is_map(args) <- validate_expires_at(args) do
      {scheduled_at, args} = Map.pop(args, :expires_at)

      args
      |> __MODULE__.new(scheduled_at: scheduled_at)
      |> Oban.insert()
    end
  end

  @impl true
  def perform(%Oban.Job{args: %{"activity_id" => id}}) do
    with %Pleroma.Activity{} = activity <- find_activity(id),
         %Pleroma.User{} = user <- find_user(activity.object.data["actor"]),
         false <- pinned_by_actor?(activity, user) do
      Pleroma.Web.CommonAPI.delete(activity.id, user)
    else
      :pinned_by_actor ->
        # if activity is pinned, schedule deletion on next day
        enqueue(%{activity_id: id, expires_at: DateTime.add(DateTime.utc_now(), 24 * 3600)})

        :ok

      error ->
        error
    end
  end

  defp enabled? do
    with false <- Pleroma.Config.get([__MODULE__, :enabled], false) do
      {:error, :expired_activities_disabled}
    end
  end

  defp validate_expires_at(%{validate: false} = args), do: Map.delete(args, :validate)

  defp validate_expires_at(args) do
    if expires_late_enough?(args[:expires_at]) do
      args
    else
      {:error, :expiration_too_close}
    end
  end

  defp find_activity(id) do
    with nil <- Pleroma.Activity.get_by_id_with_object(id) do
      {:error, :activity_not_found}
    end
  end

  defp find_user(ap_id) do
    with nil <- Pleroma.User.get_by_ap_id(ap_id) do
      {:error, :user_not_found}
    end
  end

  defp pinned_by_actor?(activity, user) do
    with true <- Pleroma.Activity.pinned_by_actor?(activity, user) do
      :pinned_by_actor
    end
  end

  def get_expiration(id) do
    from(j in Oban.Job,
      where: j.state == "scheduled",
      where: j.queue == "activity_expiration",
      where: fragment("?->>'activity_id' = ?", j.args, ^id)
    )
    |> Pleroma.Repo.one()
  end

  @spec expires_late_enough?(DateTime.t()) :: boolean()
  def expires_late_enough?(scheduled_at) do
    now = DateTime.utc_now()
    diff = DateTime.diff(scheduled_at, now, :millisecond)
    diff > :timer.hours(1)
  end
end