Revamp of the jit_builder.rb to support Fast Refresh in Bridgetown 2.0

[jaredcwhite]

I spent a bit of time on a new site running the latest Bridgetown 2.0 beta and Tailwind 4.0 beta 1. In order to support the new fast refresh feature, we need a way to hook into a site's post_write event and, if on the fast refresh path, trigger the Tailwind JIT refresh.

This is best I could get it for now. Maybe folks can play around with the concept some more. Basically fast refresh happens first and you get a browser reload right away, which is good for normal content updates, and then there's a full refresh shortly thereafter. It does mean there can be a "flash of not yet Tailwind-generated styling" as you're playing around with element classes though. I'm not really sure how to make it smoother, but at least it works. I also thought of the idea of having a --skip-tw-jit CLI option, so when you know you're just working on content and not styling per se, you can skip the extra refresh entirely.

class Builders::TailwindJit < SiteBuilder
  def build
    return if ARGV.include?("--skip-tw-jit")

    fast_refreshing = false

    hook :site, :fast_refresh do
      fast_refreshing = true
    end

    hook :site, :post_write do
      if fast_refreshing
        fast_refreshing = false
        Thread.new do
          sleep 0.75
          refresh_file = site.in_root_dir("frontend", "styles", "jit-refresh.css")
          File.write refresh_file, "/* #{Time.now.to_i} */"
        end
      end
    end
  end
end