haml_js.rb

module HamlJs
  class Filter
    def initialize(app)
      @app = app
    end

    def call(env)
      dup._call(env)
    end

    def _call(env)

      template_root = Rails.root.join("app/js/templates")
      output_root = Rails.root.join("public/javascripts/templates")

      (Dir["#{template_root}/*.haml"] + Dir["#{template_root}/**/*.haml"]).each do |file|

        file = File.expand_path(file)
        basename = File.basename(file, ".haml")

        var_name = basename
        output_file = "#{var_name}.js"

        dir = File.dirname(file.gsub("#{template_root}/", ""))
        dir = "" if dir == "."
        if dir != ""
          output_file = "#{dir}/#{output_file}"
          var_name = "#{dir.gsub("/", "_")}_#{var_name}"
        end

        output_file = File.join(output_root, output_file)

        FileUtils.mkdir_p(File.dirname(output_file))
        next unless dirty?(file, output_file)

        File.open(output_file, "w") do |f|
          f.puts "template_#{var_name} = #{compile(File.read(file)).to_json};"
        end
      end

      @app.call env
    end

    private

    def dirty?(from, to)
      File.exist?(from) && (!File.exist?(to) || File.mtime(to) < File.mtime(from))
    end

    def compile(script)
      command = "/System/Library/Frameworks/JavaScriptCore.framework/Versions/A/Resources/jsc"
      f = Tempfile.open("hamljs.js")
      f.puts "load('resources/haml.js');"
      f.puts compile_js(script)
      f.close

      execute("#{command} #{f.path}")
    ensure
      f.close! if f
    end

    def compile_js(script)
      <<-JS
        try {
          print('+' + Haml.optimize(Haml.compile(#{script.to_json})));
        } catch (e) {
          print('-' + e);
        }
      JS
    end

    def execute(command)
      out = `#{command}`.chomp
      if $?.success?
        status, result = out[0, 1], out[1..-1]
        if status == "+"
          result
        else
          raise result[/^(?:Error: )?(.*)/, 1]
        end
      else
        raise out
      end
    end
  end
end