Revert "chore: remove route /css_config (#660)"

This reverts commit f91a3b3.

lib/beacon/router.ex

@@ -139,6 +139,9 @@ defmodule Beacon.Router do
         live_session session_name, session_opts do
           get "/__beacon_media__/:file_name", Beacon.Web.MediaLibraryController, :show, assigns: %{site: opts[:site]}
 
+          # TODO: css_config-:md5 caching
+          get "/__beacon_assets__/css_config", Beacon.Web.AssetsController, :css_config, assigns: %{site: opts[:site]}
+
           get "/__beacon_assets__/css-:md5", Beacon.Web.AssetsController, :css, assigns: %{site: opts[:site]}
           get "/__beacon_assets__/js-:md5", Beacon.Web.AssetsController, :js, assigns: %{site: opts[:site]}
 

lib/beacon/runtime_css.ex

@@ -26,6 +26,16 @@ defmodule Beacon.RuntimeCSS do
     Beacon.Config.fetch!(site).css_compiler.config(site)
   end
 
+  @doc """
+  Returns the URL to fetch the CSS config used to generate the site stylesheet.
+  """
+  @spec asset_url(Site.t()) :: String.t()
+  def asset_url(site) do
+    %{endpoint: endpoint, router: router} = Beacon.Config.fetch!(site)
+    prefix = router.__beacon_scoped_prefix_for_site__(site)
+    endpoint.url() <> Beacon.Router.sanitize_path("#{prefix}/__beacon_assets__/css_config")
+  end
+
   @doc false
   def compile(site) when is_atom(site) do
     Beacon.Config.fetch!(site).css_compiler.compile(site)

lib/beacon/web/controllers/assets_controller.ex

@@ -4,7 +4,7 @@ defmodule Beacon.Web.AssetsController do
 
   import Plug.Conn
 
-  def init(asset) when asset in [:css, :js], do: asset
+  def init(asset) when asset in [:css_config, :css, :js], do: asset
 
   def call(%{assigns: %{site: site}} = conn, asset) when asset in [:css, :js] do
     {content, content_type} = content_and_type(site, asset)
@@ -22,11 +22,31 @@ defmodule Beacon.Web.AssetsController do
     |> halt()
   end
 
+  # TODO: encoding (compress) and caching
+  def call(%{assigns: %{site: site}} = conn, :css_config) do
+    {content, content_type} = content_and_type(site, :css_config)
+
+    # The static files are served for sites,
+    # and we need to disable csrf protection because
+    # serving script files is forbidden by the CSRFProtection plug.
+    conn = put_private(conn, :plug_skip_csrf_protection, true)
+
+    conn
+    |> put_resp_header("content-type", content_type)
+    |> put_resp_header("access-control-allow-origin", "*")
+    |> send_resp(200, content)
+    |> halt()
+  end
+
   defp content_and_type(site, :css) do
     {Beacon.RuntimeCSS.fetch(site), "text/css"}
   end
 
   defp content_and_type(_site, :js) do
     {Beacon.RuntimeJS.fetch(), "text/javascript"}
   end
+
+  defp content_and_type(site, :css_config) do
+    {Beacon.RuntimeCSS.config(site), "text/javascript"}
+  end
 end