pdf_file.rb

class PdfFile < ActiveRecord::Base
  belongs_to :result_list

  has_attached_file :attachment, :path => "pdf/:id/:basename.:extension"
  
  before_post_process :set_file_name

  def generate_labels(params)
    
    unless job_finish.nil?
      # mailing_list is whether to filter only mailing list contacts or not

      mailing_list = params[:mailing_list]
      setting_id = params[:from_shipping_address_id]
      
      self.attachment.destroy
      
      update_attributes(:job_start => Time.now, 
                        :job_finish => nil, 
                        :job_error => nil,
                        :label_count => 0)


      background_process(mailing_list, setting_id)
    end
    
  end
  
  def set_to_and_from_addresses(mailing_list, setting_id)
    @from_address = Setting.find(setting_id).value

    # get addresses that have a region and country
    @addresses = result_list.contacts.map(&:addresses).flatten.compact.select{|a| a.region && a.country}

    @addresses = @addresses.select{|a| a.mailing_list} if mailing_list
  end
  
  def background_process(mailing_list, setting_id)

    begin
      set_to_and_from_addresses(mailing_list, setting_id)
      
      unless @addresses.length.zero?
        shipping_label_renderer = ShippingLabelRenderer.new

        @addresses.each do |to_address|
          shipping_label_renderer.create_label(@from_address, to_address)
          self.increment!(:label_count, 1)
        end

        pdf_file = Tempfile.new("shipping_labels.pdf")
        pdf_file.write(shipping_label_renderer.output_prawn_object.render)
        
        self.attachment = pdf_file
        self.save
      end
    
    rescue => e
      update_attribute(:job_error, e)
    ensure
      update_attribute(:job_finish, Time.now)
    end

  end
  
  handle_asynchronously :background_process

  private

  def set_file_name
    # when using Tempfile, filename becomes "shipping_labels,12928,0.pdf" which becomes "shiping_labels_12928_0.pdf"
    formatted_date = self.updated_at.strftime('%m-%d-%Y')
    self.attachment.instance_write(:file_name, "shipping_labels_#{formatted_date}.pdf")
  end

end

pdf_link_renderer.rb

class PdfLinkRenderer

  include ActionView::Helpers
  include ApplicationHelper
  
  def initialize(result_list)
    @result_list = result_list
    @pdf_file = result_list.pdf_file
  end
  
  def render_link
    return generating_label_message if @pdf_file.job_finish.nil?
    return error_message if @pdf_file.job_error
    return no_labels_message if @pdf_file.label_count.to_i.zero? || !@pdf_file.attachment?
  
    link_to "download #{label_count_text} from #{label_date}", download_admin_shipping_label_path(@pdf_file), :class => 'box'
  end
  
  def generating_label_message
    @pdf_file.label_count.nil? ? "generating labels..." : "generating label #{@pdf_file.label_count} of #{@result_list.contacts.count}"
  end
  
  def error_message
    content_tag :span, "there was an error while attempting to create the labels!", :class => :error
  end

  def label_count_text
    pluralize(@pdf_file.label_count, 'label')
  end
  
  def label_date
    show_date_time(@pdf_file.updated_at, :at)
  end
  
  def no_labels_message
    "...No labels currently generated..."
  end
  
end

pdf_link_renderer_spec.rb

require 'spec_helper'

describe PdfLinkRenderer do

  def pdf_link_renderer(options = {})
    PdfLinkRenderer.new(@result_list)
  end
  
  before(:each) do
    ResultList.all.map(&:destroy)
    @result_list = ResultList.create!
    @result_list.pdf_file = PdfFile.create!
    @pdf_file = @result_list.pdf_file
  end

  it "should render a generic generating labels message when the job begins" do
    pdf_link_renderer.generating_label_message.should == "generating labels..."
  end
  
  it "should render a generating label with number message when processing a label" do
    @pdf_file.stub!(:job_finish).and_return(nil)
    @pdf_file.stub!(:label_count).and_return(100)
    @result_list.contacts.should_receive(:count).and_return(1000)
    pdf_link_renderer.render_link.should match /\d+ of \d+/    # should match "100 of 1000"
  end
  
  it "should render an error message on error" do
    @pdf_file.stub!(:job_error).and_return("ERROR!!!!!!!!")
    pdf_link_renderer.render_link.should match /error/     
  end

  it "should render a no labels message when there is no pdf" do
    pdf_link_renderer.render_link.should match /no labels/i
  end
  
  it "should render a no labels message when the count is 0" do
    @pdf_file.stub!(:label_count).and_return(0)
    pdf_link_renderer.render_link.should match /no labels/i
  end
  
  it "should render a link when there are valid labels" do
    @pdf_file.stub!(:attachment?).and_return(true)
    @pdf_file.stub!(:label_count).and_return(9999)
    pdf_link_renderer.render_link.should match /href/    
  end
end