juggle.rb

## Juggle
# 
# The refined way of combining gathering client-side javascripts.
#
# usage:
#   (in your Rakefile)
#
#   require './lib/juggle'
#   Juggle.file 'public/app.js' => 'public/libs.js' do
#       curl 'http://github.com/documentcloud/underscore/raw/1.1.1/underscore.js'
#       curl 'http://github.com/documentcloud/backbone/raw/master/backbone.js'
#       curl 'http://github.com/janl/mustache.js/raw/0.3.0/mustache.js'
#       file 'public/libs.js'
#     coffee 'app/main.coffee'
#   end
# 
# This produces `public/app.js` and also a `public/app.min.js`.
#
# good practice:
#
#   require 'rake/clean'
#   CLOBBER.add 'public/*.js'
#

require 'closure-compiler'

class Juggle
  attr_accessor :buffer

  def self.compiler
    @compiler ||= Closure::Compiler.new
  end

  def self.file(*args, &blk)
    Kernel.send(:task, *args) do |task|
      j = new
      j.instance_eval &blk
      j.write(task.name)
    end
  end

  def initialize
    self.buffer = []
  end

  def curl(url)
    self.buffer << [url, `curl --silent #{url}`]
  end

  def coffee(path)
    self.buffer << [path, `coffee --print #{path}`]
  end

  def file(path)
    self.buffer << [path, File.read(path)]
  end

  def write(file)
    File.open(file, 'w') {|f| f.puts js}
    File.open(minified_name(file), 'w') {|f| f.puts minified_js}
  end

private

  def js
    buffer.
      map {|output| "// #{output.first}\n\n#{output.last}"}.
      join("\n")
  end
  
  def minified_js
    self.class.compiler.compile js
  end
  
  def minified_name(file)
    File.join File.dirname(file),
              [File.basename(file, '.*'), '.min', File.extname(file)].join
  end

end