An App Engine proxy to the old NCSS Challenge site.

ncssproxy.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

"A Google App Engine proxy to the old NCSS Challenge website."

import re
import webapp2

from google.appengine.api import memcache, urlfetch
from urllib import urlencode

EXPIRATION_DELTA_SECONDS = 3600

IGNORE_HEADERS = frozenset([
  # Ignore hop-by-hop headers
  'connection',
  'keep-alive',
  'proxy-authenticate',
  'proxy-authorization',
  'te',
  'trailers',
  'transfer-encoding',
  'upgrade',
])


class MainHandler(webapp2.RequestHandler):
    def get(self):
        url = "http://challenge.ncss.edu.au" + self.request.path
        if self.request.query_string:
            url += "?" + self.request.query_string

        data = urlfetch.fetch(url=url, headers=self.gen_request_headers())
        if data is None:
            return self.error(404)

        self.respond(data.content)

    def post(self):
        postdata = {}
        for key in self.request.arguments():
            postdata[key] = self.request.get(key)

        data = urlfetch.fetch(
            url="http://challenge.ncss.edu.au" + self.request.path,
            payload=urlencode(postdata),
            method=urlfetch.POST,
            headers=self.gen_request_headers(),
        )
        if data is None:
            return self.error(404)

        self.respond(data.content)

    def gen_request_headers(self):
        request_headers = {}
        for key, value in self.request.headers.iteritems():
            lc_key = key.lower()
            if lc_key not in IGNORE_HEADERS:
                if lc_key == "referer":
                    request_headers.headers[key] = re.sub(r"https?://aucg-ncssproxy\.appspot\.com",
                            "http://challenge.ncss.edu.au", value)
                else:
                    request_headers.headers[key] = value
        return request_headers

    def respond(self, content):
        content = re.sub(r"http://(?:static\.)?challenge\.ncss\.edu\.au",
                          "", content)

        for key, value in data.headers.iteritems():
            if key.lower() not in IGNORE_HEADERS:
                self.response.headers[key] = value

        self.response.out.write(content)

class StaticHandler(webapp2.RequestHandler):
    def get(self):
        url = "http://static.challenge.ncss.edu.au" + self.request.path

        # memcache static to reduce load
        data = memcache.get(url)
        if data is None:
            data = urlfetch.fetch(url)
            memcache.add(url, data)

        if data is None:
            return self.error(404)

        data.content = re.sub(r"http://(?:static\.)?challenge\.ncss\.edu\.au",
                               "", data.content)

        self.response.headers["content-type"] = data.headers.get("content-type")
        self.response.out.write(data.content)

app = webapp2.WSGIApplication([
    (r"/static/.*", StaticHandler),
    (r"/.*", MainHandler)
])