images_controller.rb

require 'delayed_job'
require 'net/http'

class ImagesController < ApplicationController
  def fetch
  	components = params[:url].split('/')
  	url = clean_url(components[0])

  	filename = components[1] + params[:format]

  	custom_image_path = File.join("public", "image_cache", "custom", url.host, filename)
  	default_image_path = File.join("public", "image_cache", "default", url.host, filename)

  	file = if File.exist?(custom_image_path)
  		custom_image_path
  	elsif File.exist?(default_image_path)
  		default_image_path
  	else
  		nil
  	end

  	logger.debug("ImagesController#fetch : file is #{file.inspect}")

  	if file.present? 
  		logger.debug "getting image #{file} for #{url.host}"
  		logger.debug(File.mtime(file))
  		logger.debug "local timestamp: #{File.mtime(file)}: \nlast_modified header: #{request.headers['If-Modified-Since']}"
  		
  		if request.headers['If-Modified-Since'].blank? || File.mtime(file) > DateTime.parse(request.headers['If-Modified-Since'])
  			send_file file
  		else
	  		head :status => :not_modified
	  	end
	  	return
	end

  	job = Delayed::Job.find_by_domain(url.host)
      unless job
        logger.debug("A job for #{url.host} was not found. Enqueuing and returning 404.")
        job = Delayed::Job.enqueue(WebImageJob.new(url))
        job.domain = url.host
        job.save!
      else
        logger.debug("A job for #{url.host} was already enqueued. Ignoring and returning 404")
      end
  	head :status => :not_found
  end

	def clean_url(domain)
		url= URI.parse domain rescue URI.parse "http://#{domain}"
		url= URI.parse "http://#{domain}" if url.is_a? URI::Generic
		
		Net::HTTP.start(url.host) do |http|
			resp = http.get('/')
			case resp when Net::HTTPRedirection then
				url = URI.parse resp['location']
			end
		end

		url
	end

end