"""

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)

"""

import re

from django.http import Http404

from django.core.exceptions import ImproperlyConfigured, ViewDoesNotExist

from django.utils.datastructures import MultiValueDict

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

from django.utils.functional import memoize

from django.utils.regex_helper import normalize

from django.utils.thread_support import currentThread

try:

    reversed

except NameError:

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

    from sets import Set as set

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

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

# SCRIPT_NAME prefixes for each thread are stored here. If there's no entry for

# the current thread (which is the only one we ever access), it is assumed to

# be empty.

_prefixes = {}

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)

                if not callable(lookup_view):

                    raise AttributeError("'%s.%s' is not a callable." % (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:]

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)

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 = MultiValueDict()

    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):

                p_pattern = pattern.regex.pattern

                if p_pattern.startswith('^'):

                    p_pattern = p_pattern[1:]

                if isinstance(pattern, RegexURLResolver):

                    parent = normalize(pattern.regex.pattern)

                    for name in pattern.reverse_dict:

                        for matches, pat in pattern.reverse_dict.getlist(name):

                            new_matches = []

                            for piece, p_args in parent:

                                new_matches.extend([(piece + suffix, p_args + args) for (suffix, args) in matches])

                            self._reverse_dict.appendlist(name, (new_matches, p_pattern + pat))

                else:

                    bits = normalize(p_pattern)

                    self._reverse_dict.appendlist(pattern.callback, (bits, p_pattern))

                    self._reverse_dict.appendlist(pattern.name, (bits, p_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:

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

            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):

        if args and kwargs:

            raise ValueError("Don't mix *args and **kwargs in call to reverse()!")

        try:

            lookup_view = get_callable(lookup_view, True)

        except (ImportError, AttributeError), e:

            raise NoReverseMatch("Error importing '%s': %s." % (lookup_view, e))

        possibilities = self.reverse_dict.getlist(lookup_view)

        for possibility, pattern in possibilities:

            for result, params in possibility:

                if args:

                    if len(args) != len(params):

                        continue

                    unicode_args = [force_unicode(val) for val in args]

                    candidate =  result % dict(zip(params, unicode_args))

                else:

                    if set(kwargs.keys()) != set(params):

                        continue

                    unicode_kwargs = dict([(k, force_unicode(v)) for (k, v) in kwargs.items()])

                    candidate = result % unicode_kwargs

                if re.search(u'^%s' % pattern, candidate, re.UNICODE):

                    return candidate

        raise NoReverseMatch("Reverse for '%s' with arguments '%s' and keyword "

                "arguments '%s' not found." % (lookup_view, args, kwargs))

def resolve(path, urlconf=None):

    return get_resolver(urlconf).resolve(path)

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

    args = args or []

    kwargs = kwargs or {}

    if prefix is None:

        prefix = get_script_prefix()

    return iri_to_uri(u'%s%s' % (prefix, get_resolver(urlconf).reverse(viewname,

            *args, **kwargs)))

def clear_url_caches():

    global _resolver_cache

    global _callable_cache

    _resolver_cache.clear()

    _callable_cache.clear()

def set_script_prefix(prefix):

    """

    Sets the script prefix for the current thread.

    """

    if not prefix.endswith('/'):

        prefix += '/'

    _prefixes[currentThread()] = prefix

def get_script_prefix():

    """

    Returns the currently active script prefix. Useful for client code that

    wishes to construct their own URLs manually (although accessing the request

    instance is normally going to be a lot cleaner).

    """

    return _prefixes.get(currentThread(), u'/')