category.py

import logging
import urlparse


class Categorizor(object):
    def __init__(self, category_rule):
        """category_rule is a string of the format:
        type:parameter:modifier

        To get the base64 decoded value of the category querystring
        parameter, use:

        "querystring:category:base64"
        """
        self.rule = category_rule.split(':')

    def categorize(self, final_url):
        if self.rule[0] == 'querystring':
            try:
                qs = urlparse.parse_qs(urlparse.urlparse(final_url).query)
                param = qs[self.rule[1]][0]
                if len(self.rule) == 3:
                    if self.rule[2] == 'base64':
                        param = param.decode('base64')
                logging.debug("Got category: %s", param)
                return param
            except (KeyError, IndexError):
                return None