Sprockets compilation of assets

Gemfile

source 'http://rubygems.org'

gem 'sass'
gem 'coffee-script'
gem 'yui-compressor'
gem 'handlebars_assets'
gem 'sprockets'
gem 'rb-fsevent'

Rakefile

# Asset tasks

require 'rubygems'
require 'bundler'
require 'pathname'
require 'logger'
require 'fileutils'
require 'rb-fsevent'

# Require gems from Gemfile
Bundler.require

# Configuration
ROOT   = Pathname(File.dirname(__FILE__))
LOGGER = Logger.new(STDOUT)
BUNDLES = %w( app.js styles.css )
BUILD_DIR = ROOT.join("public/assets")
SOURCE_DIR = ROOT.join("assets")

# register handlebar templates
Sprockets.register_engine '.hbs', HandlebarsAssets::TiltHandlebars

task :default => [:compile]

# Compile all assets
task :compile => :cleanup do
	begin
		# Create a new Sprockets::Environment instance, passing in some configurations
		sprockets = Sprockets::Environment.new(ROOT) do |env|
			env.logger = LOGGER
		end

		# Append the asset paths
		sprockets.append_path(SOURCE_DIR.join('javascripts').to_s)
		sprockets.append_path(SOURCE_DIR.join('stylesheets').to_s)

		# Process and package the assets to the build directory
		BUNDLES.each do |bundle|
			assets = sprockets.find_asset(bundle)

			# split on 
			prefix, basename = assets.pathname.to_s.split('/')[-2..-1]
			realname = basename.split(".")[0..1].join(".")

			# Add digest to filename in production
			if ENV['env'] == 'production'
				basename, ext = basename.split(".")[0..1]
				realname = "#{basename}-#{assets.digest}.#{ext}"
			end

			# Write concatenated asset
			FileUtils.mkpath BUILD_DIR
			assets.write_to(BUILD_DIR.join(realname))

			# Write minified asset
			if ENV['env'] == 'production'
				Minifier.minify [:src => BUILD_DIR.join(realname), :dst => BUILD_DIR.join(realname)]
			end

			# If you want to reference a single CSS file (e.g. filename.css) instead of an entire bundle. Build a standalone package for each CSS source
			# assets.to_a.each do |asset|
			# 	# strip filename.css.foo.bar.css multiple extensions
			# 	realname = asset.pathname.basename.to_s.split(".")[0..1].join(".")
			# 	asset.write_to(BUILD_DIR.join(prefix, realname))
			# end
		end
	rescue Exception => e
		puts e.message
	end
end

# Watch source directory for file changes and compile
task :watch => :compile do
	# options = {:latency => 4, :no_defer => true }
	fsevent = FSEvent.new
	fsevent.watch SOURCE_DIR.to_s do |directories|
		puts "Detected change inside: #{directories.inspect}"

		Rake::Task["compile"].reenable
		Rake::Task["compile"].invoke
		
	end
	fsevent.run
end

# Cleanup asset directory
task :cleanup do
	dirs = Dir.glob(File.join(BUILD_DIR.join("{*.js,*.css}")))
	dirs.each do |dir|
		FileUtils.rm_rf dir
	end
end

# Minify assets
module Minifier
	def Minifier.minify(files)
		files.each do |file|
			cmd = "java -jar ../tools/yuicompressor/build/yuicompressor-2.4.6.jar #{file[:src]} -o #{file[:dst]} --charset utf-8"
			puts cmd
			ret = system(cmd) # *** SYSTEM RUN LOCAL COMMANDS ***
			raise "Minification failed for #{file}" if !ret
		end
	end
end

bundle
rake watch
rake compile env=production