Inside an email template, I want to highlight changes made to active record object

mailer_helper.rb

module MailerHelper
  def highligh_changes_made_to object, options={}
    html = ""
    attrs = options[:attrs] || object.class.attribute_names
    html << "<br/><p>"
    
    attrs.each do |attr|
      html << "<p> #{attr.to_s.humanize} : "

      if object.previous_changes.include? attr.to_s
        if object.class.columns_hash[attr.to_s].type==:text
          html << "<br/>"
          html << text_changes(object.previous_changes[attr.to_s][0], object.previous_changes[attr.to_s][1])

        else
          html << "<font color='gray'>#{object_attr object, attr, object.previous_changes[attr.to_s][0]}</font> => "
          html << "<b>#{object_attr object, attr, object.previous_changes[attr.to_s][1]}</b>"
        end

      else
        html << "#{object_attr object, attr, (object.send attr.to_sym)}"
      end

      html << "</p>"
    end
    html << "<p/><br/>"
    html.html_safe
  end

  def object_attr object, attr, foreign_key_value
    return foreign_key_value unless attr.ends_with? "_id"

    assoc = object.class.reflections.values.select{ |assoc| assoc.foreign_key==attr }.first
    return "<NotFound>" unless assoc

    assoc.klass.where(:id => foreign_key_value).first || '""'
  end

  def text_changes str1, str2
    Diffy::Diff.new( str1, str2).collect do |line| 
      case line
      when /^\+/ then
      "<b>#{line[1..-1]}</b>"

      when /^-/ then
       "<font color='gray'>#{line[1..-1]}</font>"

      when /^\// then

      else
       line

      end
    end.join("<br/>").to_s
  end
end

class ActionMailer::Base
  helper MailerHelper
end