application_assets_helper.rb

require 'grit'

module ApplicationAssetsHelper
  
  ASSETS_FOLDERS = %w[javascripts stylesheets]
  ASSET_FORMATS = {'javascripts' => :js,
                   'stylesheets' => :css}
  #LEDO?: create some sort of compile directives for the asset packager
  
  def self.included(base)
    load_asset_tag_methods
  end
    
  def self.load_asset_tag_methods
    ASSETS_FOLDERS.each do |asset_folder|
      
      assets_type = bundles_up_to_date? ? :bundled : :development
      raise ApplicationAssetsError::StaleProductionAssetsBundle if (ENV['RAILS_ENV'] == "production" and assets_type == :development)
      
      verb = (asset_folder == 'javascripts') ? :include : :link
      for group in groups_for(asset_folder) do
        class_eval <<-EOV
          def #{asset_folder.singularize}_#{group}_bundle(*args)
            #{asset_folder.singularize}_#{verb}_tag #{recursive_asset_file_list(ASSET_FORMATS[asset_folder], group, assets_type).inspect}, *args
          end
        EOV
      end
    end
  end
  
  private
    # Returns true if there is an up to date version of the packaged javascripts
    # find out if the bundled group is up to date using the commit id of both!
    def self.bundles_up_to_date?
      development_assets_commit = find_most_recent_commit
      development_assets_commit and find_most_recent_commit(:bundled) == development_assets_commit
    end
  
    # Returns a list of the folders contained in each _asset_type_/development folder
    def self.groups_for(asset_folder)
      Dir.chdir File.join(RAILS_ROOT, 'public', asset_folder, 'development') do
        dirs = Dir.glob("*")
      end
    end
  
    # Lists all the files with the specified extension in a specified folder or bundled file depending
    # if you are looking for development or bundled assets
    #LEDO: reverse lookup on formats to determine the assets_folder
    def self.recursive_asset_file_list(ext, group, assets_type = :development)
      assets_folder = ASSET_FORMATS.index(ext)
      
      Dir.chdir File.join(RAILS_ROOT, 'public', assets_folder) do
        case assets_type
          when :development 
            assets_path = File.join('development', "#{group}", "*.#{ext}") 
          when :bundled             
            assets_path = File.join('bundled', "#{group}_*.#{ext}")
        end
  
        files = Dir.glob(assets_path)
      end
    end
  
    # LEDOUBT: use it for graphics as well?
    def self.last_asset_commit_id
      ENV['RAILS_ASSET_ID'] ||= find_most_recent_commit
    end
    # Returns the hash of the most recent commit among the assets as the asset cache id
    def self.find_most_recent_commit(assets_type = :development)
      repository = Grit::Repo.new(RAILS_ROOT+'/.git')
      folders = []

      for folder in ASSETS_FOLDERS do
        folders << repository.log(repository.head.name,File.join("public", folder, "#{assets_type}"),:max_count => 1).first
      end
      
      folders.compact.empty? ? nil : folders.sort_by { |f| f.committed_date }.last.id
    end
    
end


module ApplicationAssetsError
  class Base < Exception; end
  class StaleProductionAssetsBundle < ApplicationAssetsError::Base; end
end