"""Internationalization and localization support.

This module provides internationalization (I18N) and localization (L10N)

support for your Python programs by providing an interface to the GNU gettext

message catalog library.

I18N refers to the operation by which a program is made aware of multiple

languages.  L10N refers to the adaptation of your program, once

internationalized, to the local language and cultural habits.

"""

# This module represents the integration of work, contributions, feedback, and

# suggestions from the following people:

#

# Martin von Loewis, who wrote the initial implementation of the underlying

# C-based libintlmodule (later renamed _gettext), along with a skeletal

# gettext.py implementation.

#

# Peter Funk, who wrote fintl.py, a fairly complete wrapper around intlmodule,

# which also included a pure-Python implementation to read .mo files if

# intlmodule wasn't available.

#

# James Henstridge, who also wrote a gettext.py module, which has some

# interesting, but currently unsupported experimental features: the notion of

# a Catalog class and instances, and the ability to add to a catalog file via

# a Python API.

#

# Barry Warsaw integrated these modules, wrote the .install() API and code,

# and conformed all C and Python code to Python's coding standards.

#

# Francois Pinard and Marc-Andre Lemburg also contributed valuably to this

# module.

#

# J. David Ibanez implemented plural forms. Bruno Haible fixed some bugs.

#

# TODO:

# - Lazy loading of .mo files.  Currently the entire catalog is loaded into

#   memory, but that's probably bad for large translated programs.  Instead,

#   the lexical sort of original strings in GNU .mo files should be exploited

#   to do binary searches and lazy initializations.  Or you might want to use

#   the undocumented double-hash algorithm for .mo files with hash tables, but

#   you'll need to study the GNU gettext code to do this.

#

# - Support Solaris .mo file formats.  Unfortunately, we've been unable to

#   find this format documented anywhere.

import copy, os, re, struct, sys

from errno import ENOENT

__all__ = ['NullTranslations', 'GNUTranslations', 'Catalog',

           'find', 'translation', 'install', 'textdomain', 'bindtextdomain',

           'dgettext', 'dngettext', 'gettext', 'ngettext',

           ]

_default_localedir = os.path.join(sys.prefix, 'share', 'locale')

def test(condition, true, false):

    """

    Implements the C expression:

      condition ? true : false

    Required to correctly interpret plural forms.

    """

    if condition:

        return true

    else:

        return false

def c2py(plural):

    """Gets a C expression as used in PO files for plural forms and returns a

    Python lambda function that implements an equivalent expression.

    """

    # Security check, allow only the "n" identifier

    from StringIO import StringIO

    import token, tokenize

    tokens = tokenize.generate_tokens(StringIO(plural).readline)

    try:

        danger = [x for x in tokens if x[0] == token.NAME and x[1] != 'n']

    except tokenize.TokenError:

        raise ValueError, \

              'plural forms expression error, maybe unbalanced parenthesis'

    else:

        if danger:

            raise ValueError, 'plural forms expression could be dangerous'

    # Replace some C operators by their Python equivalents

    plural = plural.replace('&&', ' and ')

    plural = plural.replace('||', ' or ')

    expr = re.compile(r'\!([^=])')

    plural = expr.sub(' not \\1', plural)

    # Regular expression and replacement function used to transform

    # "a?b:c" to "test(a,b,c)".

    expr = re.compile(r'(.*?)\?(.*?):(.*)')

    def repl(x):

        return "test(%s, %s, %s)" % (x.group(1), x.group(2),

                                     expr.sub(repl, x.group(3)))

    # Code to transform the plural expression, taking care of parentheses

    stack = ['']

    for c in plural:

        if c == '(':

            stack.append('')

        elif c == ')':

            if len(stack) == 1:

                # Actually, we never reach this code, because unbalanced

                # parentheses get caught in the security check at the

                # beginning.

                raise ValueError, 'unbalanced parenthesis in plural form'

            s = expr.sub(repl, stack.pop())

            stack[-1] += '(%s)' % s

        else:

            stack[-1] += c

    plural = expr.sub(repl, stack.pop())

    return eval('lambda n: int(%s)' % plural)

def _expand_lang(locale):

    from locale import normalize

    locale = normalize(locale)

    COMPONENT_CODESET   = 1 << 0

    COMPONENT_TERRITORY = 1 << 1

    COMPONENT_MODIFIER  = 1 << 2

    # split up the locale into its base components

    mask = 0

    pos = locale.find('@')

    if pos >= 0:

        modifier = locale[pos:]

        locale = locale[:pos]

        mask |= COMPONENT_MODIFIER

    else:

        modifier = ''

    pos = locale.find('.')

    if pos >= 0:

        codeset = locale[pos:]

        locale = locale[:pos]

        mask |= COMPONENT_CODESET

    else:

        codeset = ''

    pos = locale.find('_')

    if pos >= 0:

        territory = locale[pos:]

        locale = locale[:pos]

        mask |= COMPONENT_TERRITORY

    else:

        territory = ''

    language = locale

    ret = []

    for i in range(mask+1):

        if not (i & ~mask):  # if all components for this combo exist ...

            val = language

            if i & COMPONENT_TERRITORY: val += territory

            if i & COMPONENT_CODESET:   val += codeset

            if i & COMPONENT_MODIFIER:  val += modifier

            ret.append(val)

    ret.reverse()

    return ret

class NullTranslations:

    def __init__(self, fp=None):

        self._info = {}

        self._charset = None

        self._fallback = None

        if fp is not None:

            self._parse(fp)

    def _parse(self, fp):

        pass

    def add_fallback(self, fallback):

        if self._fallback:

            self._fallback.add_fallback(fallback)

        else:

            self._fallback = fallback

    def gettext(self, message):

        if self._fallback:

            return self._fallback.gettext(message)

        return message

    def ngettext(self, msgid1, msgid2, n):

        if self._fallback:

            return self._fallback.ngettext(msgid1, msgid2, n)

        if n == 1:

            return msgid1

        else:

            return msgid2

    def ugettext(self, message):

        if self._fallback:

            return self._fallback.ugettext(message)

        return unicode(message)

    def ungettext(self, msgid1, msgid2, n):

        if self._fallback:

            return self._fallback.ungettext(msgid1, msgid2, n)

        if n == 1:

            return unicode(msgid1)

        else:

            return unicode(msgid2)

    def info(self):

        return self._info

    def charset(self):

        return self._charset

    def install(self, unicode=False):

        import __builtin__

        __builtin__.__dict__['_'] = unicode and self.ugettext or self.gettext

class GNUTranslations(NullTranslations):

    # Magic number of .mo files

    LE_MAGIC = 0x950412deL

    BE_MAGIC = 0xde120495L

    def _parse(self, fp):

        """Override this method to support alternative .mo formats."""

        unpack = struct.unpack

        filename = getattr(fp, 'name', '')

        # Parse the .mo file header, which consists of 5 little endian 32

        # bit words.

        self._catalog = catalog = {}

        self.plural = lambda n: int(n != 1) # germanic plural by default

        buf = fp.read()

        buflen = len(buf)

        # Are we big endian or little endian?

        magic = unpack('<I', buf[:4])[0]

        if magic == self.LE_MAGIC:

            version, msgcount, masteridx, transidx = unpack('<4I', buf[4:20])

            ii = '<II'

        elif magic == self.BE_MAGIC:

            version, msgcount, masteridx, transidx = unpack('>4I', buf[4:20])

            ii = '>II'

        else:

            raise IOError(0, 'Bad magic number', filename)

        # Now put all messages from the .mo file buffer into the catalog

        # dictionary.

        for i in xrange(0, msgcount):

            mlen, moff = unpack(ii, buf[masteridx:masteridx+8])

            mend = moff + mlen

            tlen, toff = unpack(ii, buf[transidx:transidx+8])

            tend = toff + tlen

            if mend < buflen and tend < buflen:

                msg = buf[moff:mend]

                tmsg = buf[toff:tend]

            else:

                raise IOError(0, 'File is corrupt', filename)

            # See if we're looking at GNU .mo conventions for metadata

            if mlen == 0:

                # Catalog description

                # don't handle multi-lines fields here, and skip

                # lines which don't look like a header description

                # (e.g. "header: value")

                lastk = k = None

                for item in tmsg.splitlines():

                    item = item.strip()

                    if not item or not ':' in item:

                        continue

                    k, v = item.split(':', 1)

                    k = k.strip().lower()

                    v = v.strip()

                    self._info[k] = v

                    if k == 'content-type':

                        self._charset = v.split('charset=')[1]

                    elif k == 'plural-forms':

                        v = v.split(';')

                        plural = v[1].split('plural=')[1]

                        self.plural = c2py(plural)

            # Note: we unconditionally convert both msgids and msgstrs to

            # Unicode using the character encoding specified in the charset

            # parameter of the Content-Type header.  The gettext documentation

            # strongly encourages msgids to be us-ascii, but some appliations

            # require alternative encodings (e.g. Zope's ZCML and ZPT).  For

            # traditional gettext applications, the msgid conversion will

            # cause no problems since us-ascii should always be a subset of

            # the charset encoding.  We may want to fall back to 8-bit msgids

            # if the Unicode conversion fails.

            if msg.find('\x00') >= 0:

                # Plural forms

                msgid1, msgid2 = msg.split('\x00')

                tmsg = tmsg.split('\x00')

                if self._charset:

                    msgid1 = unicode(msgid1, self._charset)

                    tmsg = [unicode(x, self._charset) for x in tmsg]

                for i in range(len(tmsg)):

                    catalog[(msgid1, i)] = tmsg[i]

            else:

                if self._charset:

                    msg = unicode(msg, self._charset)

                    tmsg = unicode(tmsg, self._charset)

                catalog[msg] = tmsg

            # advance to next entry in the seek tables

            masteridx += 8

            transidx += 8

    def gettext(self, message):

        missing = object()

        tmsg = self._catalog.get(message, missing)

        if tmsg is missing:

            if self._fallback:

                return self._fallback.gettext(message)

            return message

        # Encode the Unicode tmsg back to an 8-bit string, if possible

        if self._charset:

            return tmsg.encode(self._charset)

        return tmsg

    def ngettext(self, msgid1, msgid2, n):

        try:

            tmsg = self._catalog[(msgid1, self.plural(n))]

            if self._charset:

                return tmsg.encode(self._charset)

            return tmsg

        except KeyError:

            if self._fallback:

                return self._fallback.ngettext(msgid1, msgid2, n)

            if n == 1:

                return msgid1

            else:

                return msgid2

    def ugettext(self, message):

        missing = object()

        tmsg = self._catalog.get(message, missing)

        if tmsg is missing:

            if self._fallback:

                return self._fallback.ugettext(message)

            return unicode(message)

        return tmsg

    def ungettext(self, msgid1, msgid2, n):

        try:

            tmsg = self._catalog[(msgid1, self.plural(n))]

        except KeyError:

            if self._fallback:

                return self._fallback.ungettext(msgid1, msgid2, n)

            if n == 1:

                tmsg = unicode(msgid1)

            else:

                tmsg = unicode(msgid2)

        return tmsg

# Locate a .mo file using the gettext strategy

def find(domain, localedir=None, languages=None, all=0):

    # Get some reasonable defaults for arguments that were not supplied

    if localedir is None:

        localedir = _default_localedir

    if languages is None:

        languages = []

        for envar in ('LANGUAGE', 'LC_ALL', 'LC_MESSAGES', 'LANG'):

            val = os.environ.get(envar)

            if val:

                languages = val.split(':')

                break

        if 'C' not in languages:

            languages.append('C')

    # now normalize and expand the languages

    nelangs = []

    for lang in languages:

        for nelang in _expand_lang(lang):

            if nelang not in nelangs:

                nelangs.append(nelang)

    # select a language

    if all:

        result = []

    else:

        result = None

    for lang in nelangs:

        if lang == 'C':

            break

        mofile = os.path.join(localedir, lang, 'LC_MESSAGES', '%s.mo' % domain)

        if os.path.exists(mofile):

            if all:

                result.append(mofile)

            else:

                return mofile

    return result

# a mapping between absolute .mo file path and Translation object

_translations = {}

def translation(domain, localedir=None, languages=None,

                class_=None, fallback=False):

    if class_ is None:

        class_ = GNUTranslations

    mofiles = find(domain, localedir, languages, all=1)

    if not mofiles:

        if fallback:

            return NullTranslations()

        raise IOError(ENOENT, 'No translation file found for domain', domain)