json-p proxy for any json

json_proxy.rb

#encoding: utf-8

class Object
  def try(method)
    send method if respond_to? method
  end
end

require "eventmachine"
require "evma_httpserver"
require "em-http-request"
require "cgi"
require "uri"

class JSONHTTPProxy < EM::Connection
  include EM::HttpServer
  
  def post_init
    super
    no_environment_strings
  end
  
  def process_http_request
    response = EM::DelegatedHttpResponse.new(self)
    params = @http_query_string.nil? ? Hash.new : CGI.parse(@http_query_string)
    url = [params["u"], params["url"]].delete_if{|e|e.nil?||e.length==0}.first.try(:first)
    handler = [params["jsonp"], params["h"], params["cb"], params["handler"], params["callback"]].delete_if{|e|e.nil?||e.length==0}.first.try(:first)
    if (url =~ URI::regexp).nil?
      response.status = 406
      response.send_response
    else
      http = EventMachine::HttpRequest.new( url ).get
      http.callback do
        response.status = http.response_header.status
        response.content_type "application/json"
        if handler.nil? || handler[/^[\w\d\_]+$/].nil?
          response.content = http.response
        else
          handler = "window.#{handler}"
          response.content = "#{handler}(#{http.response.chomp})"
        end
        response.send_response
      end
      http.errback do
        response.status = 500
        response.send_response
      end
    end
  end
end

EM.run{
  EM.start_server '0.0.0.0', 7070, JSONHTTPProxy
}