cookie.py

import webapp2
import logging
import re
import cgi
import jinja2
import os
import hashlib
import hmac
from google.appengine.ext import db

## see http://jinja.pocoo.org/docs/api/#autoescaping
def guess_autoescape(template_name):
   if template_name is None or '.' not in template_name:
      return False
      ext = template_name.rsplit('.', 1)[1]
      return ext in ('html', 'htm', 'xml')

JINJA_ENVIRONMENT = jinja2.Environment(
   autoescape=guess_autoescape,     ## see http://jinja.pocoo.org/docs/api/#autoescaping
    loader=jinja2.FileSystemLoader(os.path.dirname(__file__)),
    extensions=['jinja2.ext.autoescape'])



def hash_str(s):
    return hmac.new("imsosecret",str(s)).hexdigest()

def make_secure_val(s):
    return str(str(s)+"|"+hash_str(s))

def check_secure_val(h):
    s,ha=h.split('|')
    has=hash_str(s)
    if ha==has:
        return s
    else:
        return None


class Handler(webapp2.RequestHandler):
    def write(self, *items):    
        self.response.write(" : ".join(items))

    def render_str(self, template, **params):
        tplt = JINJA_ENVIRONMENT.get_template('templates/'+template)
        return tplt.render(params)

    def render(self, template, **kw):
        self.write(self.render_str(template, **kw))

class MainPage(Handler):   
    def get(self):
        logging.info("********** MainPage GET **********")
        self.response.headers['Content-Type'] = 'text/plain'
        ##1 Assign the variable 'visits' to the value of the 'visits' 
        ##1 cookie obtained from the browsers HTTP response. If the cookie 
        ##1 does not exist, set the variable 'visits' to '0'
        visits=self.request.cookies.get('visits','DNE')
        if  visits== 'DNE':
            visits=0
            visits=make_secure_val(visits)
            self.response.headers.add_header('Set-Cookie', 'visits=%s' % visits)
            ak,akh=visits.split('|')

            if int(ak)>10000:
                self.write('you da man')
            else:
                self.write('you have visited ' + str(ak) + ' times')
        ##2 If the variable visits is an integer (i.e. use str.isdigit())
        ##2 increment visits by 1
        ##2 else set visits to 0
        else:
            if not check_secure_val(visits):
                self.write('stop messing with my cookies')
            
        ##3 Add the 'Set-Cookie:' header with the value set to the 
        ##3 variable 'visits' to the HTTP response
            else:
                visits,h=visits.split('|')
                visits=str(int(visits)+1)
                visits=make_secure_val(visits)
                self.response.headers.add_header('Set-Cookie', 'visits=%s' % visits)
        
        ##4 if visits > 10000, 
        ##4   write out a congratulations message
        ##4 else
        ##4   write out a message stating how many times the user has visited
                logging.info(visits)
                ak,akh=visits.split('|')
                logging.info(ak)
                if int(ak)>10000:
                    self.write('you da man')
                else:
                    self.write('you have visited ' + str(ak) + ' times')
    def post(self):
        logging.info("DBG: MainPage POST")





application = webapp2.WSGIApplication([
    ('/', MainPage)
], debug=True)