import links content to facebook comments by mentioning this bot, you'll need to run it periodically using cronjob

readability.rb

#!/usr/bin/env ruby
# Author : Emad Elsaid (https://github.com/blazeeboy)
# **Usage** : 
# 
# * `ruby readability.rb <accesstoken>`
# this will get a long term access token from the short term one
# you can create a facebook app and get access token from here
# * `ruby readability.rb`
# will start the script
require 'open-uri'
require 'readability' # gem install ruby-readability
require 'koala' # gem install koala

# https://developers.facebook.com/tools/explorer
# scopes required : 
# user_groups, publish_stream, manage_notifications, publish_actions

APP_ID      = '*******************'
APP_SECRET  = '*******************'
NOTIFICATIONS_LIMIT = 100

# this part get the long term access token instead of the 
# short term one yo provide and writes it to a file called
# "token" to use it over and over again when you execute
# this script.
if ARGV.size > 0
  oauth = Koala::Facebook::OAuth.new(APP_ID, APP_SECRET)
    new_access_info = oauth.exchange_access_token_info ARGV.first
    File.write 'token', new_access_info['access_token']
  puts 'New Access Token written'
  exit
end

# respond to comment with mention
def respond_to(graph, post_id)

  comment_limit = 8000
  post = graph.get_object(post_id)
  link = post['link']
  return if link.empty?

  source = open(link).read
  output = Readability::Document.new(source, tags: []).content
  output = output.gsub /(\n\s*)+/, "\n"
  output = output[0...comment_limit]
  return if output.empty?

  # posting reply comment
  graph.put_object post_id, 'comments', {message: output}

end

begin
  oauth_access_token = File.read('token')
  $graph = Koala::Facebook::API.new(oauth_access_token)

  # get your name
  $name = $graph.get_object('me')['name']

  # get notifications
  notifications = []
  page = $graph.get_connections('me','notifications')
  begin
    notifications += page
  end while page = page.next_page and notifications.length<=NOTIFICATIONS_LIMIT

  # 
  # Now lets head to parse and respond to them
  # 
  puts "Notifications found : #{notifications.size}"
  notifications.reverse_each do |n|
    begin 

      if n['application'] and n['application']['name'] == 'Groups' and  n['title'].include? 'mentioned you'

        ids = n['link'].scan /([0-9]+)\/([0-9]+)/
        comment = ids.last.last
        if ids.size == 1
          respond_to $graph, ids.last.last
        end

      end
    rescue 
      # ignore it
    end

    # mark notification as read
    $graph.put_object(n['id'],'', {unread: false})
  end

# please rescue if something went wrong
# thanks,
rescue Exception => e
  puts "Error : #{e}"
end