discourse/app/controllers/highlight_js_controller.rb

# frozen_string_literal: true

class HighlightJsController < ApplicationController
  skip_before_action :preload_json,
                     :redirect_to_login_if_required,
                     :check_xhr,
                     :verify_authenticity_token,
                     only: [:show]

  before_action :apply_cdn_headers, only: [:show]

  def show
    no_cookies

    RailsMultisite::ConnectionManagement.with_hostname(params[:hostname]) do
      current_version = HighlightJs.version(SiteSetting.highlighted_languages)

      return redirect_to path(HighlightJs.path) if current_version != params[:version]

      # note, this can be slightly optimised by caching the bundled file, it cuts down on N reads
      # our nginx config caches this so in practical terms it does not really matter and keeps
      # code simpler
      languages = SiteSetting.highlighted_languages.split("|")

      highlight_js = HighlightJs.bundle(languages)

      response.headers["Last-Modified"] = 10.years.ago.httpdate
      response.headers["Content-Length"] = highlight_js.bytesize.to_s
      immutable_for 1.year

      render plain: highlight_js, disposition: nil, content_type: "application/javascript"
    end
  end
end