akkoma/lib/pleroma/plugs/instance_static.ex

defmodule Pleroma.Plugs.InstanceStatic do
  @moduledoc """
  This is a shim to call `Plug.Static` but with runtime `from` configuration.

  Mountpoints are defined directly in the module to avoid calling the configuration for every request including non-static ones.
  """
  @behaviour Plug

  def file_path(path) do
    instance_path =
      Path.join(Pleroma.Config.get([:instance, :static_dir], "instance/static/"), path)

    if File.exists?(instance_path) do
      instance_path
    else
      Path.join(Application.app_dir(:pleroma, "priv/static/"), path)
    end
  end

  @only ~w(index.html static emoji packs sounds images instance favicon.png)

  def init(opts) do
    opts
    |> Keyword.put(:from, "__unconfigured_instance_static_plug")
    |> Keyword.put(:at, "/__unconfigured_instance_static_plug")
    |> Plug.Static.init()
  end

  for only <- @only do
    at = Plug.Router.Utils.split("/")

    def call(conn = %{request_path: "/" <> unquote(only) <> _}, opts) do
      call_static(
        conn,
        opts,
        unquote(at),
        Pleroma.Config.get([:instance, :static_dir], "instance/static")
      )
    end
  end

  def call(conn, _) do
    conn
  end

  defp call_static(conn, opts, at, from) do
    opts =
      opts
      |> Map.put(:from, from)
      |> Map.put(:at, at)

    Plug.Static.call(conn, opts)
  end
end