proxy.py

#!/usr/bin/python
# coding: utf8

# Simple HTTP proxy that appends ™ to all words in response that are six characters long
# To install run 'pip install lxml'


import re
import gzip
import copy
import urllib2
import BaseHTTPServer
from StringIO import StringIO

from lxml import etree


ALL_WORDS = re.compile(r'(\b\w{6}\b)', re.UNICODE)


def add_tm(text):
    return ALL_WORDS.sub(ur"\1™", text)


def walk_and_modify_html(text):
    tree = etree.fromstring(text, etree.HTMLParser())
    for el in tree.xpath('//*'):
        if el.tag in ('script', 'style'):
            continue
        if el.text:
            el.text = add_tm(el.text)
        if el.tail:
            el.tail = add_tm(el.tail)

    return etree.tostring(tree.getroottree(), pretty_print=True, method="html")


def make_request(url):
    response = urllib2.urlopen(url)
    return response.code, copy.deepcopy(response.headers.dict), response.read()


class ProxyHandler(BaseHTTPServer.BaseHTTPRequestHandler):
    def do_GET(s):
        if s.path.startswith('/'):
            s.send_response(404)
            s.send_header('Content-Type', 'text/plain')
            s.end_headers()
            s.wfile.write("Please use this server as HTTP PROXY. There is no any resources here.")
            return

        status_code, headers, body = make_request(s.path)

        # Decode gzipped response if needed
        if headers.get('content-encoding') == 'gzip':
            headers.pop('content-encoding')
            f = gzip.GzipFile(fileobj=StringIO(body))
            body = f.read()

        # For text/html documents do substitutions
        if headers.get('content-type', '').startswith('text/html'):
            body = body.decode('utf8')
            body = walk_and_modify_html(body)

            # durty hack to load page assets using HTTP (since our proxy doesn't support CONNECT method)
            body = body.replace('https', 'http')

            body = body.encode('utf8')
            headers['content-length'] = len(body)

        s.send_response(status_code)
        for header, value in headers.items():
            s.send_header(header, value)
        s.end_headers()

        s.wfile.write(body)


if __name__ == '__main__':
    server_class = BaseHTTPServer.HTTPServer
    httpd = server_class(('0.0.0.0', 3128), ProxyHandler)
    try:
        httpd.serve_forever()
    except KeyboardInterrupt:
        pass
    httpd.server_close()