Added first stab at reverse matching to urlresolvers.py

class Resolver404(Http404):

    pass

class NoReverseMatch(Exception):

    pass

def get_mod_func(callback):

    # Converts 'django.views.news.stories.story_detail' to

    # ['django.views.news.stories', 'story_detail']

    dot = callback.rindex('.')

    return callback[:dot], callback[dot+1:]

class MatchChecker(object):

    "Class used in reverse RegexURLPattern lookup."

    def __init__(self, args, kwargs):

        self.args, self.kwargs = args, kwargs

        self.current_arg = 0

    def __call__(self, match_obj):

        # match_obj.group(1) is the contents of the parenthesis.

        # First we need to figure out whether it's a named or unnamed group.

        #

        grouped = match_obj.group(1)

        m = re.search(r'^\?P<(\w+)>(.*?)$', grouped)

        if m: # If this was a named group...

            # m.group(1) is the name of the group

            # m.group(2) is the regex.

            try:

                value = self.kwargs[m.group(1)]

            except KeyError:

                # It was a named group, but the arg was passed in as a

                # positional arg or not at all.

                try:

                    value = self.args[self.current_arg]

                    self.current_arg += 1

                except IndexError:

                    # The arg wasn't passed in.

                    raise NoReverseMatch('Not enough positional arguments passed in')

            test_regex = m.group(2)

        else: # Otherwise, this was a positional (unnamed) group.

            try:

                value = self.args[self.current_arg]

                self.current_arg += 1

            except IndexError:

                # The arg wasn't passed in.

                raise NoReverseMatch('Not enough positional arguments passed in')

            test_regex = grouped

        # Note we're using re.match here on purpose because the start of

        # to string needs to match.

        if not re.match(test_regex + '$', str(value)): # TODO: Unicode?

            raise NoReverseMatch("Value %r didn't match regular expression %r" % (value, test_regex))

        return str(value) # TODO: Unicode?

class RegexURLPattern:

    def __init__(self, regex, callback, default_args=None):

        # regex is a string representing a regular expression.

        except AttributeError, e:

            raise ViewDoesNotExist, "Tried %s in module %s. Error was: %s" % (func_name, mod_name, str(e))

    def reverse(self, viewname, *args, **kwargs):

        if viewname != self.callback:

            raise NoReverseMatch

        return self.reverse_helper(*args, **kwargs)

    def reverse_helper(self, *args, **kwargs):

        """

        Does a "reverse" lookup -- returns the URL for the given args/kwargs.

        The args/kwargs are applied to the regular expression in this

        RegexURLPattern. For example:

            >>> RegexURLPattern('^places/(\d+)/$').reverse_helper(3)

            'places/3/'

            >>> RegexURLPattern('^places/(?P<id>\d+)/$').reverse_helper(id=3)

            'places/3/'

            >>> RegexURLPattern('^people/(?P<state>\w\w)/(\w+)/$').reverse_helper('adrian', state='il')

            'people/il/adrian/'

        Raises NoReverseMatch if the args/kwargs aren't valid for the RegexURLPattern.

        """

        # TODO: Handle nested parenthesis in the following regex.

        result = re.sub(r'\(([^)]+)\)', MatchChecker(args, kwargs), self.regex.pattern)

        return result.replace('^', '').replace('$', '')

class RegexURLResolver(object):

    def __init__(self, regex, urlconf_name):

        # regex is a string representing a regular expression.

        # urlconf_name is a string representing the module containing urlconfs.

        self.regex = re.compile(regex)

        self.urlconf_name = urlconf_name

        self.callback = None

    def resolve(self, path):

        tried = []

    def resolve500(self):

        return self._resolve_special('500')

    def reverse(self, viewname, *args, **kwargs):

        for pattern in self.urlconf_module.urlpatterns:

            if pattern.callback == viewname:

                try:

                    return pattern.reverse_helper(*args, **kwargs)

                except NoReverseMatch:

                    continue

        raise NoReverseMatch