path_to_resource

path_to_resource_helper.rb

module ApplicationHelper       
  
  def path_to_resource(source)
    generate_path(source)
  end      
  
  private
  def generate_path(source)
    has_request = @controller.respond_to?(:request)
    
    unless source =~ %r{^[-a-z]+://}
      source = "/#{source}" unless source[0] == ?/

      source = rewrite_asset_path(source)

      if has_request
        unless source =~ %r{^#{ActionController::Base.relative_url_root}/}
          source = "#{ActionController::Base.relative_url_root}#{source}"
        end
      end
    end
    
    if source !~ %r{^[-a-z]+://}
      host = compute_asset_host(source)
      
      if has_request && !host.blank? && host !~ %r{^[-a-z]+://}
        host = "#{@controller.request.protocol}#{host}"
      end

      "#{host}#{source}"
    else
      source
    end
    
  end
  
  def compute_asset_host(source)
    if host = ActionController::Base.asset_host
      if host.is_a?(Proc) || host.respond_to?(:call)
        case host.is_a?(Proc) ? host.arity : host.method(:call).arity
        when 2
          request = @controller.respond_to?(:request) && @controller.request
          host.call(source, request)
        else
          host.call(source)
        end
      else
        (host =~ /%d/) ? host % (source.hash % 4) : host
      end
    end
  end
  
end