Extract largest image thumbnail from url using node and cheerio

gistfile1.coffee

cheerio = require('cheerio')
Shred = require('shred')
shred = new Shred()
http = require('http')
URL = require('url')

server = http.createServer (request, response) ->
  url = URL.parse(request.url, true)
  urlToDiscover = url.query['url']
  startDiscovery urlToDiscover, (theImageURL) ->
    if theImageURL?
      response.writeHead(200, "Content-Type": 'application/json')
      response.end(JSON.stringify(theImageURL))
    else
      console.log("Did not find image for #{urlToDiscover}")
      response.writeHead(404, "Cant find theImage")
      response.end()
    
server.listen(process.env.PORT || 5000, '0.0.0.0')  

startDiscovery = (url, cb) ->
  shred.get 
    url:  url
    on:
      redirect: (response) ->
        discoverImage(response.request.url, null, cb)
      200:  (response) ->
        discoverImage(response.request.url, response.content.data, cb)
          

discoverImage = (url, data, cb) ->
  discoveredURL = discoverImageFromURL(url)
  if data
    discoveredURL ||= discoverImageFromData(url, data)
  discoveredURL = cleanURL(url, discoveredURL)
  cb(discoveredURL)
  
cleanURL = (baseURL, discoveredURL) ->
  return null unless discoveredURL
  return "#{baseURL}#{discoveredURL}" if discoveredURL.indexOf("/") == 0
  return discoveredURL
  
discoverImageFromURL = (url) -> 
  console.log(url.indexOf('yfrog'))
  if url.indexOf('yfrog') != -1
    return url + ":medium"
    
discoverImageFromData = (url, data) ->
  $ = cheerio.load(data)
  images = $('img')
  maxImage = null
  maxDimension = 0
  for image in images
    currDimension = $(image).attr('width') * $(image).attr('height')
    if currDimension > maxDimension
      maxDimension = currDimension
      maxImage = image
      
  return $(maxImage).attr('src')