"Translation helper functions"

import locale
import os
import re
import sys
import gettext as gettext_module
from cStringIO import StringIO
from django.utils.functional import lazy

try:
    import threading
    hasThreads = True
except ImportError:
    hasThreads = False

if hasThreads:
    currentThread = threading.currentThread
else:
    def currentThread():
        return 'no threading'

# Translations are cached in a dictionary for every language+app tuple.
# The active translations are stored by threadid to make them thread local.
_translations = {}
_active = {}

# The default translation is based on the settings file.
_default = None

# This is a cache for normalised accept-header languages to prevent multiple
# file lookups when checking the same locale on repeated requests.
_accepted = {}

# Format of Accept-Language header values. From RFC 2616, section 14.4 and 3.9.
accept_language_re = re.compile(r'''
        ([A-Za-z]{1,8}(?:-[A-Za-z]{1,8})*|\*)   # "en", "en-au", "x-y-z", "*"
        (?:;q=(0(?:\.\d{,3})?|1(?:.0{,3})?))?   # Optional "q=1.00", "q=0.8"
        (?:\s*,\s*|$)                            # Multiple accepts per header.
        ''', re.VERBOSE)

def to_locale(language, to_lower=False):
    "Turns a language name (en-us) into a locale name (en_US)."
    p = language.find('-')
    if p >= 0:
        if to_lower:
            return language[:p].lower()+'_'+language[p+1:].lower()
        else:
            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. Django uses a defined DEFAULT_CHARSET as the output charset on
    Python 2.4. With Python 2.3, use DjangoTranslation23.
    """
    def __init__(self, *args, **kw):
        from django.conf import settings
        gettext_module.GNUTranslations.__init__(self, *args, **kw)
        # Starting with Python 2.4, there's a function to define
        # the output charset. Before 2.4, the output charset is
        # identical with the translation file charset.
        try:
            self.set_output_charset(settings.DEFAULT_CHARSET)
        except AttributeError:
            pass
        self.django_output_charset = settings.DEFAULT_CHARSET
        self.__language = '??'

    def merge(self, other):
        self._catalog.update(other._catalog)

    def set_language(self, language):
        self.__language = language

    def language(self):
        return self.__language

    def __repr__(self):
        return "<DjangoTranslation lang:%s>" % self.__language

class DjangoTranslation23(DjangoTranslation):
    """
    Compatibility class that is only used with Python 2.3.
    Python 2.3 doesn't support set_output_charset on translation objects and
    needs this wrapper class to make sure input charsets from translation files
    are correctly translated to output charsets.

    With a full switch to Python 2.4, this can be removed from the source.
    """
    def gettext(self, msgid):
        res = self.ugettext(msgid)
        return res.encode(self.django_output_charset)

    def ngettext(self, msgid1, msgid2, n):
        res = self.ungettext(msgid1, msgid2, n)
        return res.encode(self.django_output_charset)

def translation(language):
    """
    Returns a translation object.

    This translation object will be constructed out of multiple GNUTranslations
    objects by merging their catalogs. It will construct a object for the
    requested language and add a fallback to the default language, if it's
    different from the requested language.
    """
    global _translations

    t = _translations.get(language, None)
    if t is not None:
        return t

    from django.conf import settings

    # set up the right translation class
    klass = DjangoTranslation
    if sys.version_info < (2, 4):
        klass = DjangoTranslation23

    globalpath = os.path.join(os.path.dirname(sys.modules[settings.__module__].__file__), 'locale')

    if settings.SETTINGS_MODULE is not None:
        parts = settings.SETTINGS_MODULE.split('.')
        project = __import__(parts[0], {}, {}, [])
        projectpath = os.path.join(os.path.dirname(project.__file__), 'locale')
    else:
        projectpath = None

    def _fetch(lang, fallback=None):

        global _translations

        loc = to_locale(lang)

        res = _translations.get(lang, None)
        if res is not None:
            return res

        def _translation(path):
            try:
                t = gettext_module.translation('django', path, [loc], klass)
                t.set_language(lang)
                return t
            except IOError, e:
                return None

        res = _translation(globalpath)

        def _merge(path):
            t = _translation(path)
            if t is not None:
                if res is None:
                    return t
                else:
                    res.merge(t)
            return res

        if hasattr(settings, 'LOCALE_PATHS'):
            for localepath in settings.LOCALE_PATHS:
                if os.path.isdir(localepath):
                    res = _merge(localepath)

        if projectpath and os.path.isdir(projectpath):
            res = _merge(projectpath)

        for appname in settings.INSTALLED_APPS:
            p = appname.rfind('.')
            if p >= 0:
                app = getattr(__import__(appname[:p], {}, {}, [appname[p+1:]]), appname[p+1:])
            else:
                app = __import__(appname, {}, {}, [])

            apppath = os.path.join(os.path.dirname(app.__file__), 'locale')

            if os.path.isdir(apppath):
                res = _merge(apppath)

        if res is None:
            if fallback is not None:
                res = fallback
            else:
                return gettext_module.NullTranslations()
        _translations[lang] = res
        return res

    default_translation = _fetch(settings.LANGUAGE_CODE)
    current_translation = _fetch(language, fallback=default_translation)

    return current_translation

def activate(language):
    """
    Fetches the translation object for a given tuple of application name and
    language and installs it as the current translation object for the current
    thread.
    """
    _active[currentThread()] = translation(language)

def deactivate():
    """
    Deinstalls the currently active translation object so that further _ calls
    will resolve against the default translation object, again.
    """
    global _active
    if _active.has_key(currentThread()):
        del _active[currentThread()]

def get_language():
    "Returns the currently selected language."
    t = _active.get(currentThread(), None)
    if t is not None:
        try:
            return to_language(t.language())
        except AttributeError:
            pass
    # If we don't have a real translation object, assume it's the default language.
    from django.conf import settings
    return settings.LANGUAGE_CODE

def get_language_bidi():
    """
    Returns selected language's BiDi layout.
    False = left-to-right layout
    True = right-to-left layout
    """
    from django.conf import settings
    return get_language() in settings.LANGUAGES_BIDI

def catalog():
    """
    This function 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, _active
    t = _active.get(currentThread(), None)
    if t is not None:
        return t
    if _default is None:
        from django.conf import settings
        _default = translation(settings.LANGUAGE_CODE)
    return _default

def gettext(message):
    """
    This function will be patched into the builtins module to provide the _
    helper function. It will use the current thread as a discriminator 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, _active
    t = _active.get(currentThread(), None)
    if t is not None:
        return t.gettext(message)
    if _default is None:
        from django.conf import settings
        _default = translation(settings.LANGUAGE_CODE)
    return _default.gettext(message)

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 ngettext(singular, plural, number):
    """
    Returns the translation of either the singular or plural, based on the number.
    """
    global _default, _active

    t = _active.get(currentThread(), None)
    if t is not None:
        return t.ngettext(singular, plural, number)
    if _default is None:
        from django.conf import settings
        _default = translation(settings.LANGUAGE_CODE)
    return _default.ngettext(singular, plural, number)

gettext_lazy = lazy(gettext, str)
ngettext_lazy = lazy(ngettext, str)

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. This is
    only used for language codes from either the cookies or session.
    """
    from django.conf import settings
    globalpath = os.path.join(os.path.dirname(sys.modules[settings.__module__].__file__), 'locale')
    if gettext_module.find('django', globalpath, [to_locale(lang_code)]) is not None:
        return True
    else:
        return False

def get_language_from_request(request):
    """
    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.
    """
    global _accepted
    from django.conf import settings
    globalpath = os.path.join(os.path.dirname(sys.modules[settings.__module__].__file__), 'locale')
    supported = dict(settings.LANGUAGES)

    if hasattr(request, 'session'):
        lang_code = request.session.get('django_language', None)
        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('django_language')
    if lang_code and lang_code in supported and check_for_language(lang_code):
        return lang_code

    accept = request.META.get('HTTP_ACCEPT_LANGUAGE', '')
    for lang, unused in parse_accept_lang_header(accept):
        if lang == '*':
            break

        # We have a very restricted form for our language files (no encoding
        # specifier, since they all must be UTF-8 and only one possible
        # language each time. So we avoid the overhead of gettext.find() and
        # look up the MO file manually.

        normalized = locale.locale_alias.get(to_locale(lang, True))
        if not normalized:
            continue

        # Remove the default encoding from locale_alias
        normalized = normalized.split('.')[0]

        if normalized in _accepted:
            # We've seen this locale before and have an MO file for it, so no
            # need to check again.
            return _accepted[normalized]

        for lang in (normalized, normalized.split('_')[0]):
            if lang not in supported:
                continue
            langfile = os.path.join(globalpath, lang, 'LC_MESSAGES',
                    'django.mo')
            if os.path.exists(langfile):
                _accepted[normalized] = lang
            return lang

    return settings.LANGUAGE_CODE

def get_date_formats():
    """
    This function checks whether translation files provide a translation for some
    technical message ID to store date and time formats. If it doesn't contain
    one, the formats provided in the settings will be used.
    """
    from django.conf import settings
    date_format = _('DATE_FORMAT')
    datetime_format = _('DATETIME_FORMAT')
    time_format = _('TIME_FORMAT')
    if date_format == 'DATE_FORMAT':
        date_format = settings.DATE_FORMAT
    if datetime_format == 'DATETIME_FORMAT':
        datetime_format = settings.DATETIME_FORMAT
    if time_format == 'TIME_FORMAT':
        time_format = settings.TIME_FORMAT
    return date_format, datetime_format, time_format

def get_partial_date_formats():
    """
    This function checks whether translation files provide a translation for some
    technical message ID to store partial date formats. If it doesn't contain
    one, the formats provided in the settings will be used.
    """
    from django.conf import settings
    year_month_format = _('YEAR_MONTH_FORMAT')
    month_day_format = _('MONTH_DAY_FORMAT')
    if year_month_format == 'YEAR_MONTH_FORMAT':
        year_month_format = settings.YEAR_MONTH_FORMAT
    if month_day_format == 'MONTH_DAY_FORMAT':
        month_day_format = settings.MONTH_DAY_FORMAT
    return year_month_format, month_day_format

def install():
    """
    Installs the gettext function as the default translation function under
    the name '_'.
    """
    __builtins__['_'] = gettext

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)

inline_re = re.compile(r"""^\s*trans\s+((?:".*?")|(?:'.*?'))\s*""")
block_re = re.compile(r"""^\s*blocktrans(?:\s+|$)""")
endblock_re = re.compile(r"""^\s*endblocktrans$""")
plural_re = re.compile(r"""^\s*plural$""")
constant_re = re.compile(r"""_\(((?:".*?")|(?:'.*?'))\)""")
def templatize(src):
    """
    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
    out = StringIO()
    intrans = False
    inplural = False
    singular = []
    plural = []
    for t in Lexer(src, None).tokenize():
        if intrans:
            if t.token_type == TOKEN_BLOCK:
                endbmatch = endblock_re.match(t.contents)
                pluralmatch = plural_re.match(t.contents)
                if endbmatch:
                    if inplural:
                        out.write(' ngettext(%r,%r,count) ' % (''.join(singular), ''.join(plural)))
                        for part in singular:
                            out.write(blankout(part, 'S'))
                        for part in plural:
                            out.write(blankout(part, 'P'))
                    else:
                        out.write(' gettext(%r) ' % ''.join(singular))
                        for part in singular:
                            out.write(blankout(part, 'S'))
                    intrans = False
                    inplural = False
                    singular = []
                    plural = []
                elif pluralmatch:
                    inplural = True
                else:
                    raise SyntaxError, "Translation blocks must not include other block tags: %s" % t.contents
            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:
                if inplural:
                    plural.append(t.contents)
                else:
                    singular.append(t.contents)
        else:
            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("'")
                    out.write(' gettext(%r) ' % g)
                elif bmatch:
                    intrans = True
                    inplural = False
                    singular = []
                    plural = []
                elif cmatches:
                    for cmatch in cmatches:
                        out.write(' _(%s) ' % cmatch)
                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'))
            else:
                out.write(blankout(t.contents, 'X'))
    return out.getvalue()

def string_concat(*strings):
    """"
    lazy variant of string concatenation, needed for translations that are
    constructed from multiple parts. Handles lazy strings and non-strings by
    first turning all arguments to strings, before joining them.
    """
    return ''.join([str(el) for el in strings])

string_concat = lazy(string_concat, str)

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)
    if pieces[-1]:
        return []
    for i in range(0, len(pieces) - 1, 3):
        first, lang, priority = pieces[i : i + 3]
        if first:
            return []
        priority = priority and float(priority) or 1.0
        result.append((lang, priority))
    result.sort(lambda x, y: -cmp(x[1], y[1]))
    return result

