text: """Translation helper functions."""
  from __future__ import unicode_literals
  
  from collections import OrderedDict
  import os
  import re
  import sys
  import gettext as gettext_module
  from threading import local
  import warnings
  
  from django.apps import apps
  from django.conf import settings
  from django.core.exceptions import AppRegistryNotReady
  from django.dispatch import receiver
  from django.test.signals import setting_changed
  from django.utils.deprecation import RemovedInDjango19Warning
  from django.utils.encoding import force_text
  from django.utils._os import upath
  from django.utils.safestring import mark_safe, SafeData
  from django.utils import six, lru_cache
  from django.utils.six import StringIO
  from django.utils.translation import TranslatorCommentWarning, trim_whitespace, LANGUAGE_SESSION_KEY
  
  
  # Translations are cached in a dictionary for every language.
  # The active translations are stored by threadid to make them thread local.
  _translations = {}
  _active = local()
  
  # The default translation is based on the settings file.
  _default = None
  
  # This is a cache of settings.LANGUAGES in an OrderedDict for easy lookups by
  # key
  _supported = None
  
  # magic gettext number to separate context from message
  CONTEXT_SEPARATOR = "\x04"
  
  # Format of Accept-Language header values. From RFC 2616, section 14.4 and 3.9
  # and RFC 3066, section 2.1
  accept_language_re = re.compile(r'''
          ([A-Za-z]{1,8}(?:-[A-Za-z0-9]{1,8})*|\*)      # "en", "en-au", "x-y-z", "es-419", "*"
          (?:\s*;\s*q=(0(?:\.\d{,3})?|1(?:.0{,3})?))?   # Optional "q=1.00", "q=0.8"
          (?:\s*,\s*|$)                                 # Multiple accepts per header.
          ''', re.VERBOSE)
  
  language_code_re = re.compile(r'^[a-z]{1,8}(?:-[a-z0-9]{1,8})*$', re.IGNORECASE)
  
  language_code_prefix_re = re.compile(r'^/([\w-]+)(/|$)')
  
  # some browsers use deprecated locales. refs #18419
  _BROWSERS_DEPRECATED_LOCALES = {
      'zh-cn': 'zh-hans',
      'zh-tw': 'zh-hant',
  }
  
  _DJANGO_DEPRECATED_LOCALES = _BROWSERS_DEPRECATED_LOCALES
  
  
  @receiver(setting_changed)
  def reset_cache(**kwargs):
      """
      Reset global state when LANGUAGES setting has been changed, as some
      languages should no longer be accepted.
      """
      if kwargs['setting'] in ('LANGUAGES', 'LANGUAGE_CODE'):
          global _supported
          _supported = None
          check_for_language.cache_clear()
          get_supported_language_variant.cache_clear()
  
  
  def to_locale(language, to_lower=False):
      """
      Turns a language name (en-us) into a locale name (en_US). If 'to_lower' is
      True, the last component is lower-cased (en_us).
      """
      p = language.find('-')
      if p >= 0:
          if to_lower:
              return language[:p].lower() + '_' + language[p + 1:].lower()
          else:
              # Get correct locale for sr-latn
              if len(language[p + 1:]) > 2:
                  return language[:p].lower() + '_' + language[p + 1].upper() + language[p + 2:].lower()
              return language[:p].lower() + '_' + language[p + 1:].upper()
      else:
          return language.lower()
  
  
  def to_language(locale):
      """Turns a locale name (en_US) into a language name (en-us)."""
      p = locale.find('_')
      if p >= 0:
          return locale[:p].lower() + '-' + locale[p + 1:].lower()
      else:
          return locale.lower()
  
  
  class DjangoTranslation(gettext_module.GNUTranslations):
      """
      This class sets up the GNUTranslations context with regard to output
      charset.
  
      This translation object will be constructed out of multiple GNUTranslations
      objects by merging their catalogs. It will construct an object for the
      requested language and add a fallback to the default language, if it's
      different from the requested language.
      """
      def __init__(self, language):
          """Create a GNUTranslations() using many locale directories"""
          gettext_module.GNUTranslations.__init__(self)
  
          self.__language = language
          self.__to_language = to_language(language)
          self.__locale = to_locale(language)
          self.plural = lambda n: int(n != 1)
  
          self._init_translation_catalog()
          self._add_installed_apps_translations()
          self._add_local_translations()
          self._add_fallback()
  
      def __repr__(self):
          return "<DjangoTranslation lang:%s>" % self.__language
  
      def _new_gnu_trans(self, localedir, use_null_fallback=True):
          """
          Returns a mergeable gettext.GNUTranslations instance.
  
          A convenience wrapper. By default gettext uses 'fallback=False'.
          Using param `use_null_fallback` to avoid confusion with any other
          references to 'fallback'.
          """
          translation = gettext_module.translation(
              domain='django',
              localedir=localedir,
              languages=[self.__locale],
              codeset='utf-8',
              fallback=use_null_fallback)
          if not hasattr(translation, '_catalog'):
              # provides merge support for NullTranslations()
              translation._catalog = {}
              translation._info = {}
          return translation
  
      def _init_translation_catalog(self):
          """Creates a base catalog using global django translations."""
          settingsfile = upath(sys.modules[settings.__module__].__file__)
          localedir = os.path.join(os.path.dirname(settingsfile), 'locale')
          use_null_fallback = True
          if self.__language == settings.LANGUAGE_CODE:
              # default lang should be present and parseable, if not
              # gettext will raise an IOError (refs #18192).
              use_null_fallback = False
          translation = self._new_gnu_trans(localedir, use_null_fallback)
          self._info = translation._info.copy()
          self._catalog = translation._catalog.copy()
  
      def _add_installed_apps_translations(self):
          """Merges translations from each installed app."""
          try:
              app_configs = reversed(list(apps.get_app_configs()))
          except AppRegistryNotReady:
              raise AppRegistryNotReady(
                  "The translation infrastructure cannot be initialized before the "
                  "apps registry is ready. Check that you don't make non-lazy "
                  "gettext calls at import time.")
          for app_config in app_configs:
              localedir = os.path.join(app_config.path, 'locale')
              translation = self._new_gnu_trans(localedir)
              self.merge(translation)
  
      def _add_local_translations(self):
          """Merges translations defined in LOCALE_PATHS."""
          for localedir in reversed(settings.LOCALE_PATHS):
              translation = self._new_gnu_trans(localedir)
              self.merge(translation)
  
      def _add_fallback(self):
          """Sets the GNUTranslations() fallback with the default language."""
          # Don't set a fallback for the default language or for
          # en-us (as it's empty, so it'll ALWAYS fall back to the default
          # language; found this as part of #21498, as we set en-us for
          # management commands)
          if self.__language == settings.LANGUAGE_CODE or self.__language == "en-us":
              return
          default_translation = translation(settings.LANGUAGE_CODE)
          self.add_fallback(default_translation)
  
      def merge(self, other):
          """Merge another translation into this catalog."""
          self._catalog.update(other._catalog)
  
      def language(self):
          """Returns the translation language."""
          return self.__language
  
      def to_language(self):
          """Returns the translation language name."""
          return self.__to_language
  
  
  def translation(language):
      """
      Returns a translation object.
      """
      global _translations
      if language not in _translations:
          _translations[language] = DjangoTranslation(language)
      return _translations[language]
  
  
  def activate(language):
      """
      Fetches the translation object for a given language and installs it as the
      current translation object for the current thread.
      """
      if language in _DJANGO_DEPRECATED_LOCALES:
          msg = ("The use of the language code '%s' is deprecated. "
                 "Please use the '%s' translation instead.")
          warnings.warn(msg % (language, _DJANGO_DEPRECATED_LOCALES[language]),
                        RemovedInDjango19Warning, stacklevel=2)
      _active.value = translation(language)
  
  
  def deactivate():
      """
      Deinstalls the currently active translation object so that further _ calls
      will resolve against the default translation object, again.
      """
      if hasattr(_active, "value"):
          del _active.value
  
  
  def deactivate_all():
      """
      Makes the active translation object a NullTranslations() instance. This is
      useful when we want delayed translations to appear as the original string
      for some reason.
      """
      _active.value = gettext_module.NullTranslations()
  
  
  def get_language():
      """Returns the currently selected language."""
      t = getattr(_active, "value", None)
      if t is not None:
          try:
              return t.to_language()
          except AttributeError:
              pass
      # If we don't have a real translation object, assume it's the default language.
      return settings.LANGUAGE_CODE
  
  
  def get_language_bidi():
      """
      Returns selected language's BiDi layout.
  
      * False = left-to-right layout
      * True = right-to-left layout
      """
      base_lang = get_language().split('-')[0]
      return base_lang in settings.LANGUAGES_BIDI
  
  
  def catalog():
      """
      Returns the current active catalog for further processing.
      This can be used if you need to modify the catalog or want to access the
      whole message catalog instead of just translating one string.
      """
      global _default
  
      t = getattr(_active, "value", None)
      if t is not None:
          return t
      if _default is None:
          _default = translation(settings.LANGUAGE_CODE)
      return _default
  
  
  def do_translate(message, translation_function):
      """
      Translates 'message' using the given 'translation_function' name -- which
      will be either gettext or ugettext. It uses the current thread to find the
      translation object to use. If no current translation is activated, the
      message will be run through the default translation object.
      """
      global _default
  
      # str() is allowing a bytestring message to remain bytestring on Python 2
      eol_message = message.replace(str('\r\n'), str('\n')).replace(str('\r'), str('\n'))
      t = getattr(_active, "value", None)
      if t is not None:
          result = getattr(t, translation_function)(eol_message)
      else:
          if _default is None:
              _default = translation(settings.LANGUAGE_CODE)
          result = getattr(_default, translation_function)(eol_message)
      if isinstance(message, SafeData):
          return mark_safe(result)
      return result
  
  
  def gettext(message):
      """
      Returns a string of the translation of the message.
  
      Returns a string on Python 3 and an UTF-8-encoded bytestring on Python 2.
      """
      return do_translate(message, 'gettext')
  
  if six.PY3:
      ugettext = gettext
  else:
      def ugettext(message):
          return do_translate(message, 'ugettext')
  
  
  def pgettext(context, message):
      msg_with_ctxt = "%s%s%s" % (context, CONTEXT_SEPARATOR, message)
      result = ugettext(msg_with_ctxt)
      if CONTEXT_SEPARATOR in result:
          # Translation not found
          # force unicode, because lazy version expects unicode
          result = force_text(message)
      return result
  
  
  def gettext_noop(message):
      """
      Marks strings for translation but doesn't translate them now. This can be
      used to store strings in global variables that should stay in the base
      language (because they might be used externally) and will be translated
      later.
      """
      return message
  
  
  def do_ntranslate(singular, plural, number, translation_function):
      global _default
  
      t = getattr(_active, "value", None)
      if t is not None:
          return getattr(t, translation_function)(singular, plural, number)
      if _default is None:
          _default = translation(settings.LANGUAGE_CODE)
      return getattr(_default, translation_function)(singular, plural, number)
  
  
  def ngettext(singular, plural, number):
      """
      Returns a string of the translation of either the singular or plural,
      based on the number.
  
      Returns a string on Python 3 and an UTF-8-encoded bytestring on Python 2.
      """
      return do_ntranslate(singular, plural, number, 'ngettext')
  
  if six.PY3:
      ungettext = ngettext
  else:
      def ungettext(singular, plural, number):
          """
          Returns a unicode strings of the translation of either the singular or
          plural, based on the number.
          """
          return do_ntranslate(singular, plural, number, 'ungettext')
  
  
  def npgettext(context, singular, plural, number):
      msgs_with_ctxt = ("%s%s%s" % (context, CONTEXT_SEPARATOR, singular),
                        "%s%s%s" % (context, CONTEXT_SEPARATOR, plural),
                        number)
      result = ungettext(*msgs_with_ctxt)
      if CONTEXT_SEPARATOR in result:
          # Translation not found
          result = ungettext(singular, plural, number)
      return result
  
  
  def all_locale_paths():
      """
      Returns a list of paths to user-provides languages files.
      """
      globalpath = os.path.join(
          os.path.dirname(upath(sys.modules[settings.__module__].__file__)), 'locale')
      return [globalpath] + list(settings.LOCALE_PATHS)
  
  
  @lru_cache.lru_cache(maxsize=1000)
  def check_for_language(lang_code):
      """
      Checks whether there is a global language file for the given language
      code. This is used to decide whether a user-provided language is
      available.
  
      lru_cache should have a maxsize to prevent from memory exhaustion attacks,
      as the provided language codes are taken from the HTTP request. See also
      <https://www.djangoproject.com/weblog/2007/oct/26/security-fix/>.
      """
      # First, a quick check to make sure lang_code is well-formed (#21458)
      if not language_code_re.search(lang_code):
          return False
      for path in all_locale_paths():
          if gettext_module.find('django', path, [to_locale(lang_code)]) is not None:
              return True
      return False
  
  
  @lru_cache.lru_cache(maxsize=1000)
  def get_supported_language_variant(lang_code, strict=False):
      """
      Returns the language-code that's listed in supported languages, possibly
      selecting a more generic variant. Raises LookupError if nothing found.
  
      If `strict` is False (the default), the function will look for an alternative
      country-specific variant when the currently checked is not found.
  
      lru_cache should have a maxsize to prevent from memory exhaustion attacks,
      as the provided language codes are taken from the HTTP request. See also
      <https://www.djangoproject.com/weblog/2007/oct/26/security-fix/>.
      """
      global _supported
      if _supported is None:
          _supported = OrderedDict(settings.LANGUAGES)
      if lang_code:
          # some browsers use deprecated language codes -- #18419
          replacement = _BROWSERS_DEPRECATED_LOCALES.get(lang_code)
          if lang_code not in _supported and replacement in _supported:
              return replacement
          # if fr-ca is not supported, try fr.
          generic_lang_code = lang_code.split('-')[0]
          for code in (lang_code, generic_lang_code):
              if code in _supported and check_for_language(code):
                  return code
          if not strict:
              # if fr-fr is not supported, try fr-ca.
              for supported_code in _supported:
                  if supported_code.startswith(generic_lang_code + '-'):
                      return supported_code
      raise LookupError(lang_code)
  
  
  def get_language_from_path(path, strict=False):
      """
      Returns the language-code if there is a valid language-code
      found in the `path`.
  
      If `strict` is False (the default), the function will look for an alternative
      country-specific variant when the currently checked is not found.
      """
      regex_match = language_code_prefix_re.match(path)
      if not regex_match:
          return None
      lang_code = regex_match.group(1)
      try:
          return get_supported_language_variant(lang_code, strict=strict)
      except LookupError:
          return None
  
  
  def get_language_from_request(request, check_path=False):
      """
      Analyzes the request to find what language the user wants the system to
      show. Only languages listed in settings.LANGUAGES are taken into account.
      If the user requests a sublanguage where we have a main language, we send
      out the main language.
  
      If check_path is True, the URL path prefix will be checked for a language
      code, otherwise this is skipped for backwards compatibility.
      """
      global _supported
      if _supported is None:
          _supported = OrderedDict(settings.LANGUAGES)
  
      if check_path:
          lang_code = get_language_from_path(request.path_info)
          if lang_code is not None:
              return lang_code
  
      if hasattr(request, 'session'):
          lang_code = request.session.get(LANGUAGE_SESSION_KEY)
          if lang_code in _supported and lang_code is not None and check_for_language(lang_code):
              return lang_code
  
      lang_code = request.COOKIES.get(settings.LANGUAGE_COOKIE_NAME)
  
      try:
          return get_supported_language_variant(lang_code)
      except LookupError:
          pass
  
      accept = request.META.get('HTTP_ACCEPT_LANGUAGE', '')
      for accept_lang, unused in parse_accept_lang_header(accept):
          if accept_lang == '*':
              break
  
          if not language_code_re.search(accept_lang):
              continue
  
          try:
              return get_supported_language_variant(accept_lang)
          except LookupError:
              continue
  
      try:
          return get_supported_language_variant(settings.LANGUAGE_CODE)
      except LookupError:
          return settings.LANGUAGE_CODE
  
  dot_re = re.compile(r'\S')
  
  
  def blankout(src, char):
      """
      Changes every non-whitespace character to the given char.
      Used in the templatize function.
      """
      return dot_re.sub(char, src)
  
  
  context_re = re.compile(r"""^\s+.*context\s+((?:"[^"]*?")|(?:'[^']*?'))\s*""")
  inline_re = re.compile(r"""^\s*trans\s+((?:"[^"]*?")|(?:'[^']*?'))(\s+.*context\s+((?:"[^"]*?")|(?:'[^']*?')))?\s*""")
  block_re = re.compile(r"""^\s*blocktrans(\s+.*context\s+((?:"[^"]*?")|(?:'[^']*?')))?(?:\s+|$)""")
  endblock_re = re.compile(r"""^\s*endblocktrans$""")
  plural_re = re.compile(r"""^\s*plural$""")
  constant_re = re.compile(r"""_\(((?:".*?")|(?:'.*?'))\)""")
  one_percent_re = re.compile(r"""(?<!%)%(?!%)""")
  
  
  def templatize(src, origin=None):
      """
      Turns a Django template into something that is understood by xgettext. It
      does so by translating the Django translation tags into standard gettext
      function invocations.
      """
      from django.template import (Lexer, TOKEN_TEXT, TOKEN_VAR, TOKEN_BLOCK,
              TOKEN_COMMENT, TRANSLATOR_COMMENT_MARK)
      src = force_text(src, settings.FILE_CHARSET)
      out = StringIO('')
      message_context = None
      intrans = False
      inplural = False
      trimmed = False
      singular = []
      plural = []
      incomment = False
      comment = []
      lineno_comment_map = {}
      comment_lineno_cache = None
  
      def join_tokens(tokens, trim=False):
          message = ''.join(tokens)
          if trim:
              message = trim_whitespace(message)
          return message
  
      for t in Lexer(src, origin).tokenize():
          if incomment:
              if t.token_type == TOKEN_BLOCK and t.contents == 'endcomment':
                  content = ''.join(comment)
                  translators_comment_start = None
                  for lineno, line in enumerate(content.splitlines(True)):
                      if line.lstrip().startswith(TRANSLATOR_COMMENT_MARK):
                          translators_comment_start = lineno
                  for lineno, line in enumerate(content.splitlines(True)):
                      if translators_comment_start is not None and lineno >= translators_comment_start:
                          out.write(' # %s' % line)
                      else:
                          out.write(' #\n')
                  incomment = False
                  comment = []
              else:
                  comment.append(t.contents)
          elif intrans:
              if t.token_type == TOKEN_BLOCK:
                  endbmatch = endblock_re.match(t.contents)
                  pluralmatch = plural_re.match(t.contents)
                  if endbmatch:
                      if inplural:
                          if message_context:
                              out.write(' npgettext(%r, %r, %r,count) ' % (
                                  message_context,
                                  join_tokens(singular, trimmed),
                                  join_tokens(plural, trimmed)))
                          else:
                              out.write(' ngettext(%r, %r, count) ' % (
                                  join_tokens(singular, trimmed),
                                  join_tokens(plural, trimmed)))
                          for part in singular:
                              out.write(blankout(part, 'S'))
                          for part in plural:
                              out.write(blankout(part, 'P'))
                      else:
                          if message_context:
                              out.write(' pgettext(%r, %r) ' % (
                                  message_context,
                                  join_tokens(singular, trimmed)))
                          else:
                              out.write(' gettext(%r) ' % join_tokens(singular,
                                                                      trimmed))
                          for part in singular:
                              out.write(blankout(part, 'S'))
                      message_context = None
                      intrans = False
                      inplural = False
                      singular = []
                      plural = []
                  elif pluralmatch:
                      inplural = True
                  else:
                      filemsg = ''
                      if origin:
                          filemsg = 'file %s, ' % origin
                      raise SyntaxError("Translation blocks must not include other block tags: %s (%sline %d)" % (t.contents, filemsg, t.lineno))
              elif t.token_type == TOKEN_VAR:
                  if inplural:
                      plural.append('%%(%s)s' % t.contents)
                  else:
                      singular.append('%%(%s)s' % t.contents)
              elif t.token_type == TOKEN_TEXT:
                  contents = one_percent_re.sub('%%', t.contents)
                  if inplural:
                      plural.append(contents)
                  else:
                      singular.append(contents)
  
          else:
              # Handle comment tokens (`{# ... #}`) plus other constructs on
              # the same line:
              if comment_lineno_cache is not None:
                  cur_lineno = t.lineno + t.contents.count('\n')
                  if comment_lineno_cache == cur_lineno:
                      if t.token_type != TOKEN_COMMENT:
                          for c in lineno_comment_map[comment_lineno_cache]:
                              filemsg = ''
                              if origin:
                                  filemsg = 'file %s, ' % origin
                              warn_msg = ("The translator-targeted comment '%s' "
                                  "(%sline %d) was ignored, because it wasn't the last item "
                                  "on the line.") % (c, filemsg, comment_lineno_cache)
                              warnings.warn(warn_msg, TranslatorCommentWarning)
                          lineno_comment_map[comment_lineno_cache] = []
                  else:
                      out.write('# %s' % ' | '.join(lineno_comment_map[comment_lineno_cache]))
                  comment_lineno_cache = None
  
              if t.token_type == TOKEN_BLOCK:
                  imatch = inline_re.match(t.contents)
                  bmatch = block_re.match(t.contents)
                  cmatches = constant_re.findall(t.contents)
                  if imatch:
                      g = imatch.group(1)
                      if g[0] == '"':
                          g = g.strip('"')
                      elif g[0] == "'":
                          g = g.strip("'")
                      g = one_percent_re.sub('%%', g)
                      if imatch.group(2):
                          # A context is provided
                          context_match = context_re.match(imatch.group(2))
                          message_context = context_match.group(1)
                          if message_context[0] == '"':
                              message_context = message_context.strip('"')
                          elif message_context[0] == "'":
                              message_context = message_context.strip("'")
                          out.write(' pgettext(%r, %r) ' % (message_context, g))
                          message_context = None
                      else:
                          out.write(' gettext(%r) ' % g)
                  elif bmatch:
                      for fmatch in constant_re.findall(t.contents):
                          out.write(' _(%s) ' % fmatch)
                      if bmatch.group(1):
                          # A context is provided
                          context_match = context_re.match(bmatch.group(1))
                          message_context = context_match.group(1)
                          if message_context[0] == '"':
                              message_context = message_context.strip('"')
                          elif message_context[0] == "'":
                              message_context = message_context.strip("'")
                      intrans = True
                      inplural = False
                      trimmed = 'trimmed' in t.split_contents()
                      singular = []
                      plural = []
                  elif cmatches:
                      for cmatch in cmatches:
                          out.write(' _(%s) ' % cmatch)
                  elif t.contents == 'comment':
                      incomment = True
                  else:
                      out.write(blankout(t.contents, 'B'))
              elif t.token_type == TOKEN_VAR:
                  parts = t.contents.split('|')
                  cmatch = constant_re.match(parts[0])
                  if cmatch:
                      out.write(' _(%s) ' % cmatch.group(1))
                  for p in parts[1:]:
                      if p.find(':_(') >= 0:
                          out.write(' %s ' % p.split(':', 1)[1])
                      else:
                          out.write(blankout(p, 'F'))
              elif t.token_type == TOKEN_COMMENT:
                  if t.contents.lstrip().startswith(TRANSLATOR_COMMENT_MARK):
                      lineno_comment_map.setdefault(t.lineno,
                                                    []).append(t.contents)
                      comment_lineno_cache = t.lineno
              else:
                  out.write(blankout(t.contents, 'X'))
      return out.getvalue()
  
  
  def parse_accept_lang_header(lang_string):
      """
      Parses the lang_string, which is the body of an HTTP Accept-Language
      header, and returns a list of (lang, q-value), ordered by 'q' values.
  
      Any format errors in lang_string results in an empty list being returned.
      """
      result = []
      pieces = accept_language_re.split(lang_string.lower())
      if pieces[-1]:
          return []
      for i in range(0, len(pieces) - 1, 3):
          first, lang, priority = pieces[i:i + 3]
          if first:
              return []
          if priority:
              try:
                  priority = float(priority)
              except ValueError:
                  return []
          if not priority:        # if priority is 0.0 at this point make it 1.0
              priority = 1.0
          result.append((lang, priority))
      result.sort(key=lambda k: k[1], reverse=True)
      return result
  