attachment.rb

class Video < ActiveRecord::Base
  after_save :background_process_attachment

  def background_process_attachment
    video = self.class.find(id)
    return if video.nil?

    to_process = []
    to_fetch   = []

    %w(attachment trailer watermarked wmv).each do |name|
      to_fetch   << name if video.send(:"#{name}_source_url_changed?") && !video.send(:"#{name}_source_url").blank?
      to_process << name if video.send(:"#{name}_changed?")
    end

    if video.state == 'error' && !(to_fetch.empty? && to_process.empty?)
      video.update_column(:state, 'waiting')
      video.update_column(:error_message, nil)
    end

    if not to_process.empty?
      Resque.enqueue(ProcessMultipleAttachmentsJob, self.class.name, video.id, to_process)
    elsif not to_fetch.empty?
      Resque.enqueue(FetchMultipleAttachmentsJob, self.class.name, video.id, to_fetch)
    end
  end
end