import re
from django import template
from django.utils import translation
from django.template import defaultfilters

register = template.Library()

def _numdict(s):
    return dict([(unicode(num), code) for num, code in enumerate(s)])

LANGUAGE_DIGITS = {
    'ar': _numdict(u'\u0660\u0661\u0662\u0663\u0664\u0665\u0666\u0667\u0668\u0669'),
    'fa': _numdict(u'\u06f0\u06f1\u06f2\u06f3\u06f4\u06f5\u06f6\u06f7\u06f8\u06f9'),
}

digit = re.compile('\d')

def i18n_digits(uc_str, lang=None):
    """
    Translate the digits a unicode string into the digits used in the given
    language. If no language is given, the language code from the current
    language is used.
    """
    if lang is None:
        lang = translation.get_language()
    if lang not in LANGUAGE_DIGITS:
        return uc_str

    table = LANGUAGE_DIGITS[lang]
    def replace_digit(m):
        return table[m.group()]
    return digit.sub(replace_digit, uc_str)
i18n_digits = defaultfilters.stringfilter(i18n_digits)
register.filter('i18n_digits', i18n_digits)