init.rb

Merb::BootLoader.after_app_loads do 
  require 'red'
  require 'merb_red'
  # Update on every request in development mode
  # But only on app load for production
  Red::MerbPlugin.ensure_installation!
      
  if Merb.env == 'development'
    Merb.logger.info "Hooking Red Into Request"
# I'm looking at how the sass/plugin does re-generating on every request
# I'll work something up tonight
    DmGraph::Main.use_red_dev_filter!
  else
    Red.update_javascripts
  end
end

red-merb.rb

module Red
  def self.update_javascripts
    Merb.logger.info "Updating JavaScripts"
    red_dir = "#{Merb.root}/public/javascripts/red/"
    (Dir.glob("%s/*.red" % red_dir) + Dir.glob("%s/*.rb" % red_dir)).each do |filepath|
      Merb.logger.info("Updating JavaScript: #{filepath}")
      basename = File.basename(filepath).gsub(/\.(rb|red)/,'')
      if self.update?(basename)
        Red.init(filepath)
        js_output = File.read(filepath).translate_to_sexp_array.red!
        ruby_js = compile_ruby_js_source
        pre = Red.debug ? "try{" : ""
        post = Red.debug ? "}catch(e){if(e.__class__){m$raise(e);};$ee=e;var m=e.message.match(/([^\\$]+)\\.m\\$(\\w+)\\sis\\snot\\sa\\sfunction/);if(m){m$raise(c$NoMethodError,$q('undefined method \"'+m[2]+'\" for '+m[1]));};var c=e.message.match(/([\\s\\S]+)\\sis\\sundefined/);if(c){c=c[1].replace(/\\./g,'::').replace(/c\\$/g,'');m$raise(c$NameError,$q('uninitialized constant '+c));};}" : ""
        File.open("public/javascripts/%s.js" % basename, 'w') {|f| f.write(pre + ruby_js + js_output + post)}
      end
    end
  end
  
  def self.update?(basename)
    return true unless File.exists?('public/javascripts/%s.js' % basename)
    return (File.mtime('public/javascripts/red/%s.red' % basename) rescue File.mtime('public/javascripts/red/%s.rb' % basename)) > File.mtime('public/javascripts/%s.js' % basename)
  end
  
  module MerbPlugin
    def self.root
      @root||= Pathname.new(Merb.root/'public'/'javascripts'/'red')
    end
    
    def self.ensure_installation!
      installed = root.instance_eval { mkdir unless exist? }
      Merb.logger.info "Installed Red::Merb" unless installed.nil?
    end
  end
end