"""

This module converts requested URLs to callback view functions.

RegexURLResolver is the main class here. Its resolve() method takes a URL (as

a string) and returns a tuple in this format:

    (view_function, function_args, function_kwargs)

"""

from django.http import Http404

from django.core.exceptions import ImproperlyConfigured, ViewDoesNotExist

from django.utils.encoding import iri_to_uri, force_unicode, smart_str

from django.utils.functional import memoize

import re

try:

    reversed

except NameError:

    from django.utils.itercompat import reversed     # Python 2.3 fallback

_resolver_cache = {} # Maps urlconf modules to RegexURLResolver instances.

_callable_cache = {} # Maps view and url pattern names to their view functions.

class Resolver404(Http404):

    pass

class NoReverseMatch(Exception):

    # Don't make this raise an error when used in a template.

    silent_variable_failure = True

def get_callable(lookup_view, can_fail=False):

    """

    Convert a string version of a function name to the callable object.

    If the lookup_view is not an import path, it is assumed to be a URL pattern

    label and the original string is returned.

    If can_fail is True, lookup_view might be a URL pattern label, so errors

    during the import fail and the string is returned.

    """

    if not callable(lookup_view):

        try:

            # Bail early for non-ASCII strings (they can't be functions).

            lookup_view = lookup_view.encode('ascii')

            mod_name, func_name = get_mod_func(lookup_view)

            if func_name != '':

                lookup_view = getattr(__import__(mod_name, {}, {}, ['']), func_name)

        except (ImportError, AttributeError):

            if not can_fail:

                raise

        except UnicodeEncodeError:

            pass

    return lookup_view

get_callable = memoize(get_callable, _callable_cache, 1)

def get_resolver(urlconf):

    if urlconf is None:

        from django.conf import settings

        urlconf = settings.ROOT_URLCONF

    return RegexURLResolver(r'^/', urlconf)

get_resolver = memoize(get_resolver, _resolver_cache, 1)

def get_mod_func(callback):

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

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

    try:

        dot = callback.rindex('.')

    except ValueError:

        return callback, ''

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

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

    """

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

    The args/kwargs are applied to the given compiled regular expression.

    For example:

        >>> reverse_helper(re.compile('^places/(\d+)/$'), 3)

        'places/3/'

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

        'places/3/'

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

        'people/il/adrian/'

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

    """

    # TODO: Handle nested parenthesis in the following regex.

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

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

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, re.UNICODE)

        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 + '$', force_unicode(value), re.UNICODE):

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

        return force_unicode(value)

class RegexURLPattern(object):

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

        # regex is a string representing a regular expression.

        # callback is either a string like 'foo.views.news.stories.story_detail'

        # which represents the path to a module and a view function name, or a

        # callable object (view).

        self.regex = re.compile(regex, re.UNICODE)

        if callable(callback):

            self._callback = callback

        else:

            self._callback = None

            self._callback_str = callback

        self.default_args = default_args or {}

        self.name = name

    def __repr__(self):

        return '<%s %s %s>' % (self.__class__.__name__, self.name, self.regex.pattern)

    def add_prefix(self, prefix):

        """

        Adds the prefix string to a string-based callback.

        """

        if not prefix or not hasattr(self, '_callback_str'):

            return

        self._callback_str = prefix + '.' + self._callback_str

    def resolve(self, path):

        match = self.regex.search(path)

        if match:

            # If there are any named groups, use those as kwargs, ignoring

            # non-named groups. Otherwise, pass all non-named arguments as

            # positional arguments.

            kwargs = match.groupdict()

            if kwargs:

                args = ()

            else:

                args = match.groups()

            # In both cases, pass any extra_kwargs as **kwargs.

            kwargs.update(self.default_args)

            return self.callback, args, kwargs

    def _get_callback(self):

        if self._callback is not None:

            return self._callback

        try:

            self._callback = get_callable(self._callback_str)

        except ImportError, e:

            mod_name, _ = get_mod_func(self._callback_str)

            raise ViewDoesNotExist, "Could not import %s. Error was: %s" % (mod_name, str(e))

        except AttributeError, e:

            mod_name, func_name = get_mod_func(self._callback_str)

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

        return self._callback

    callback = property(_get_callback)

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

        mod_name, func_name = get_mod_func(viewname)

        try:

            lookup_view = getattr(__import__(mod_name, {}, {}, ['']), func_name)

        except (ImportError, AttributeError):

            raise NoReverseMatch

        if lookup_view != self.callback:

            raise NoReverseMatch

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

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

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

class RegexURLResolver(object):

    def __init__(self, regex, urlconf_name, default_kwargs=None):

        # regex is a string representing a regular expression.

        # urlconf_name is a string representing the module containing urlconfs.

        self.regex = re.compile(regex, re.UNICODE)

        self.urlconf_name = urlconf_name

        self.callback = None

        self.default_kwargs = default_kwargs or {}

        self._reverse_dict = {}

    def __repr__(self):

        return '<%s %s %s>' % (self.__class__.__name__, self.urlconf_name, self.regex.pattern)

    def _get_reverse_dict(self):

        if not self._reverse_dict and hasattr(self.urlconf_module, 'urlpatterns'):

            for pattern in reversed(self.urlconf_module.urlpatterns):

                if isinstance(pattern, RegexURLResolver):

                    for key, value in pattern.reverse_dict.iteritems():

                        self._reverse_dict[key] = (pattern,) + value

                else:

                    self._reverse_dict[pattern.callback] = (pattern,)

                    self._reverse_dict[pattern.name] = (pattern,)

        return self._reverse_dict

    reverse_dict = property(_get_reverse_dict)

    def resolve(self, path):

        tried = []

        match = self.regex.search(path)

        if match:

            new_path = path[match.end():]

            for pattern in self.urlconf_module.urlpatterns:

                try:

                    sub_match = pattern.resolve(new_path)

                except Resolver404, e:

                    tried.extend([(pattern.regex.pattern + '   ' + t) for t in e.args[0]['tried']])

                else:

                    if sub_match:

                        sub_match_dict = dict([(smart_str(k), v) for k, v in match.groupdict().items()])

                        sub_match_dict.update(self.default_kwargs)

                        for k, v in sub_match[2].iteritems():

                            sub_match_dict[smart_str(k)] = v

                        return sub_match[0], sub_match[1], sub_match_dict

                    tried.append(pattern.regex.pattern)

            raise Resolver404, {'tried': tried, 'path': new_path}

    def _get_urlconf_module(self):

        try:

            return self._urlconf_module

        except AttributeError:

            try:

                self._urlconf_module = __import__(self.urlconf_name, {}, {}, [''])

            except Exception, e:

                # Either an invalid urlconf_name, such as "foo.bar.", or some

                # kind of problem during the actual import.

                raise ImproperlyConfigured, "Error while importing URLconf %r: %s" % (self.urlconf_name, e)

            return self._urlconf_module

    urlconf_module = property(_get_urlconf_module)

    def _get_url_patterns(self):

        return self.urlconf_module.urlpatterns

    url_patterns = property(_get_url_patterns)

    def _resolve_special(self, view_type):

        callback = getattr(self.urlconf_module, 'handler%s' % view_type)

        mod_name, func_name = get_mod_func(callback)

        try:

            return getattr(__import__(mod_name, {}, {}, ['']), func_name), {}

        except (ImportError, AttributeError), e:

            raise ViewDoesNotExist, "Tried %s. Error was: %s" % (callback, str(e))

    def resolve404(self):

        return self._resolve_special('404')

    def resolve500(self):

        return self._resolve_special('500')

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

        try:

            lookup_view = get_callable(lookup_view, True)

        except (ImportError, AttributeError):

            raise NoReverseMatch

        if lookup_view in self.reverse_dict:

            return u''.join([reverse_helper(part.regex, *args, **kwargs) for part in self.reverse_dict[lookup_view]])

        raise NoReverseMatch

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

        sub_match = self.reverse(lookup_view, *args, **kwargs)

        result = reverse_helper(self.regex, *args, **kwargs)

        return result + sub_match

def resolve(path, urlconf=None):

    return get_resolver(urlconf).resolve(path)

def reverse(viewname, urlconf=None, args=None, kwargs=None):

    args = args or []

    kwargs = kwargs or {}

    return iri_to_uri(u'/' + get_resolver(urlconf).reverse(viewname, *args, **kwargs))