Check the contents of an element on a remote page and send an SMS if it has changed

page-element-watcher.rb

# page-element-watcher
#
# Checks the contents of an element on a remote page and sends an SMS if it has changed


require 'nokogiri'
require 'open-uri'
require 'redis'
require 'twilio-ruby'

# Constants
URL = 'http://www.sammlung-boros.de/visit/book-tour.html?L=1#item_0'
ELEMENT = '.accordion_item:first-child'
REDIS_KEY = "page-element-watcher:element-contents:#{URL}:#{ELEMENT}"
TWILIO_SID = ''
TWILIO_TOKEN = ''
SMS_FROM = ''
SMS_TO = %w{}

# Globals
@redis = Redis.new
@twilio = Twilio::REST::Client.new(TWILIO_SID, TWILIO_TOKEN)



doc = Nokogiri::HTML(open(URL))
element_contents = doc.css(ELEMENT).to_s

previous_element_contents = @redis.get(REDIS_KEY)

if element_contents != previous_element_contents
  message = "page-element-watcher: Page #{URL} element #{ELEMENT} has changed!"
  @twilio.messages.create(
    from: SMS_FROM,
    to: SMS_TO,
    body: message
  )

  @redis.set(REDIS_KEY, element_contents)
end