# Appends a modification timestamp to the url of assets that are output using any of the AssetTagHelper methods.
#
# For example:
#   image_tag('smiley.jpg') # => <img src="/images/smiley.jpg?1129811151" />
#
# For background as to why this may be required:
# http://overstimulate.com/articles/2005/09/08/web-apps-ajax-distribution-problem

# $Id$
# $URL$

module AssetTimestampingPlugin #:nodoc:
  module ActionView
    module Helpers
      module AssetTagHelper
        def self.included(base)
          base.send(:include, InstanceMethods)
          base.class_eval do
            alias :compute_public_path_without_timestamp :compute_public_path
            alias :compute_public_path :timestamped_compute_public_path        
          end
        end
        module InstanceMethods #:nodoc:
          private
            def timestamped_compute_public_path(source, dir, ext)
              public_path = compute_public_path_without_timestamp(source,dir,ext)
              if not source.include?('?')
                file_paths = ["#{RAILS_ROOT}/public/#{dir}/#{source}",
                              "#{RAILS_ROOT}/public/#{dir}/#{source}.#{ext}"]
                for path in file_paths
                  if File.exists?(path)
                    return public_path << '?' + File.stat(path).mtime.to_i.to_s
                  end
                end
              end
              public_path
            end
        end
      end
    end
  end
end