##
# Send a protected file using the web server (via the x-sendfile header).
# Takes the absolute file system path to the file and, optionally, a MIME type.
#
def send_file(filepath, options = {})
  options[:content_type] ||= "application/force-download"
  response.headers['Content-Type'] = options[:content_type]
  response.headers['Content-Disposition'] = "attachment; filename="#{File.basename(filepath)}""
  response.headers['X-Sendfile'] = filepath
  response.headers['Content-length'] = File.size(filepath)
  render :nothing => true
end

##
# Private file download: check permission first.
#
def download
  product = Product.find_by_filename!(params[:filename])
  if current_user.has_bought?(product) or current_user.is_superuser?
    if File.exist?(path = product.filepath)
      send_file path, :content_type => "application/pdf"
    else
      not_found
    end
  else
    not_authorized
  end
end