bundle.rake

# Put Google's javascript closure_compesser.jar in ./lib
namespace :bundle do
  desc "Bundle javascript"
  task :js do
    compression_method = "closure"

    require 'lib/js_minimizer' if compression_method != "closure"
    closure_path = File.join(Rails.root,'lib/closure_compresser.jar')

    paths = get_top_level_directories('/public/javascripts')

    targets = []
    paths.each do |bundle_directory|
      bundle_name = File.basename(bundle_directory)
      files = recursive_file_list(bundle_directory, ".js")
      next if files.empty? || bundle_name == 'dev'
      target = File.join(Rails.root, "/public/javascripts/bundle_#{bundle_name}.js")

      if compression_method == "closure"
        puts "java -jar #{closure_path} --js #{files.join(" --js ")} --js_output_file #{target}"
        `java -jar #{closure_path} --js #{files.join(" --js ")} --js_output_file #{target}`
      else
        File.open(target, 'w+') do |f|
          f.puts JSMinimizer.minimize_files(*files)
        end
      end
      targets << target
    end

    targets.each do |target|
      puts "=> bundled js at #{target}"
    end
  end

  def get_top_level_directories(base_path)
    Dir[File.join(Rails.root, base_path, "*")].map do |path|
      path if File.directory?(path)
    end.compact
  end

end

bundle_helper.rb

require 'find'

# A helper to manage which script tags to use in development vs production.
module BundleHelper

  # Use this to indicate the local name of a js lib, and a publicly hosted one. The local (unminimized) will be included in development mode, and the public one used for production
  #
  # Examples:
  #
  #     != javascript_dev ['jquery-1.4.1', 'http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js']
  #     != javascript_dev ['jquery-ui', 'http://ajax.googleapis.com/ajax/libs/jqueryui/1.7.2/jquery-ui.min.js']
  #
  def javascript_dev(*sources)
    output = ""
    sources = sources.to_a
    sources.each do |pair|
      output << javascript_src_tag(Rails.env == 'development' ? "dev/#{pair[0]}" : pair[1], {})
    end
    output
  end

  #  This will include every file under 'public/javascript/{source}/*'. In development mode, it will have one <script> tag per file. In production, it will have one script tag for 'public/javascript/{source}.js'
  #
  #  Example:
  #
  #     != javascript_bundle 'common'
  #
  def javascript_bundle(*sources)
    sources = sources.to_a
    bundle_files? ? javascript_include_bundles(sources) : javascript_include_files(sources)
  end

  # This method assumes you have manually bundled js using a rake command
  # or similar. So there better be bundle_* files.
  def javascript_include_bundles(bundles)
    output = ""
    bundles.each do |bundle|
      output << javascript_src_tag("bundle_#{bundle}", {}) + "\n"
    end
    output
  end

  def javascript_include_files(bundles)
    output = ""
    bundles.each do |bundle|
      files = recursive_file_list("public/javascripts/#{bundle}", ".js")
      files.each do |file|
        file = file.gsub('public/javascripts/', '')
        output << javascript_src_tag(file, {}) + "\n"
      end
    end
    output
  end

  def bundle_files?
    Rails.env == 'production' || Rails.env == 'staging' || params[:bundle] || cookies[:bundle] == "yes"
  end

  def recursive_file_list(basedir, extname)
    Dir["#{basedir}/**/*#{extname}"]
  end

end