# coding=utf-8
"""
I18n.

To mark strings for transalation::

    from abilian.i18n import _
    _(u'message to translate')

Use :data:`_` for gettext, :data:`_l` for lazy_gettext, :data:`_n` for
ngettext.

:data:`Babel extension<babel>` support multiple translation paths. This
allows to add more catalogs to search for translations, in LIFO
order. This feature can be used to override some translations in a
custom application, be providing a catalog with messages to override::

    current_app.extensions['babel'].add_translations('abilian.core')

See :meth:`add_translations<Babel.add_translations>`.

To extract messages to build the message catalog template (.pot), use the
following "`-k`" parameters:

.. code-block:: bash

    $ pybabel extract -F babel.cfg -k "_n:1,2" -k "_l" -o "msg.pot" "src"


This can be made easier by placing in `setup.cfg`:

.. code-block:: ini

    [extract_messages]
    mapping_file = babel.cfg
    keywords = _n:1,2 _l
    output-file = msg.pot
    input-dirs = src


And just type:

.. code-block:: bash

    $ python setup.py extract_messages


"""
from __future__ import absolute_import, print_function, division

import os
import re
from gettext import GNUTranslations
import importlib
import unicodedata
from pathlib import Path
from contextlib import contextmanager
from datetime import datetime

import pytz
from babel import Locale
from babel.localedata import locale_identifiers
from babel.support import Translations as BaseTranslations
from babel.dates import LOCALTZ, get_timezone, get_timezone_gmt
from flask import g, request, _request_ctx_stack, current_app, render_template
import flask_babel
from flask_babel import (
    Babel as BabelBase,
    gettext, lazy_gettext, ngettext,
)

__all__ = [
  'babel',
  'gettext', '_',
  'lazy_gettext', '_l', 'localeselector',
  'ngettext', '_n',
  'set_locale',
  'timezoneselector',
  'VALID_LANGUAGES_CODE',
  'render_template_i18n'
]

#: gettext alias
_ = gettext

#: lazy_gettext alias
_l = lazy_gettext
#: ngettext alias
_n = ngettext

#: accepted languages codes
VALID_LANGUAGES_CODE = frozenset(lang for lang in locale_identifiers()
                                 if len(lang) == 2)

def get_default_locale():
  return current_app.extensions['babel'].default_locale


def _get_locale():
  locale = flask_babel.get_locale()
  if locale is None:
    locale = get_default_locale()
  return locale


def __gettext_territory(code):
  locale = _get_locale()
  return (
      locale.territories.get(code)
      or get_default_locale().territories.get(code))

#: get localized territory name
def country_name(code):
  return __gettext_territory(code)

#: lazy version of :func:`country_name`
def lazy_country_name(code):
  from speaklater import make_lazy_string
  return make_lazy_string(__gettext_territory, code)


def default_country():
  return current_app.config.get('DEFAULT_COUNTRY')


def country_choices(first=None, default_country_first=True):
  """
  Return a list of (code, countries), alphabetically sorted on localized
  country name.

  :param first: Country code to be placed at the top
  """
  locale = _get_locale()
  territories = [(code, name) for code, name in locale.territories.iteritems()
                 if len(code) == 2] # skip 3-digit regions

  if first is None and default_country_first:
    first = default_country()

  def sortkey(item):
    if first is not None and item[0] == first:
      return u'0'
    return to_lower_ascii(item[1])

  territories.sort(key=sortkey)
  return territories


def supported_app_locales():
  """
  language codes and labels supported by current application

  :return: an iterable of `(:class:`babel.Locale`, label)`, label being the
  locale language human name in current locale.
  """
  locale = _get_locale()
  codes = current_app.config['BABEL_ACCEPT_LANGUAGES']
  return ((Locale.parse(code), locale.languages.get(code, code))
          for code in codes)


def timezones_choices():
  """
  Timezones values and their labels for current locale.

  :return: an iterable of `(code, label)`, code being a timezone code and label
  the timezone name in current locale.
  """
  utcnow = pytz.utc.localize(datetime.utcnow())
  locale = _get_locale()
  for tz in sorted(pytz.common_timezones):
    tz = get_timezone(tz)
    now = tz.normalize(utcnow.astimezone(tz))
    label = u'({}) {}'.format(get_timezone_gmt(now, locale=locale), tz.zone)
    yield (tz, label) #get_timezone_name(tz, locale=locale))


class Babel(BabelBase):
  """
  Allow to load translations from other modules
  """
  _translations_paths = None

  def __init__(self, *args, **kwargs):
    BabelBase.__init__(self, *args, **kwargs)

  def init_app(self, app):
    super(Babel, self).init_app(app)
    self._translations_paths = [
      (os.path.join(app.root_path, 'translations'), 'messages')
    ]

  def add_translations(self, module_name,
                       translations_dir='translations',
                       domain='messages'):
    """
    Adds translations from external module. For example::

        babel.add_translations('abilian.core')

    Will add translations files from `abilian.core` module.
    """
    module = importlib.import_module(module_name)
    for path in (Path(p, translations_dir) for p in module.__path__):
      if not (path.exists() and path.is_dir()):
        continue

      if not os.access(unicode(path), os.R_OK):
        self.app.logger.warning(
          "Babel translations: read access not allowed {}, skipping."
          "".format(
            repr(unicode((path)).encode('utf-8')))
        )
        continue

      self._translations_paths.append((unicode(path), domain))


class Translations(BaseTranslations):
  """
  Merge only non-empty translations.

  This avoids having uncomplete catalog that "clear" existing translations, when
  used with :func:`_get_translations_multi_paths`.
  """
  def merge(self, translations):
    if isinstance(translations, GNUTranslations):

      for msgkey, msgstr in translations._catalog.items():
        msgid = msgkey

        if isinstance(msgkey, tuple):
          msgid = msgkey[0]

        msgstr = msgstr.strip()
        if msgkey in self._catalog and (msgid == msgstr):
          # when msgstr is empty, compile_catalog sets msgstr = msgid so this is
          # probable an existing translation that would be "erased" by msgid
          # string: skip it.

          # logger.debug('Catalog: %r, skip msgkey: %r, existing: %r',
          #                translations, msgkey, self._catalog[msgkey])
          continue

        self._catalog[msgkey] = msgstr

      if isinstance(translations, BaseTranslations):
        self.files.extend(translations.files)

    return self


def _get_translations_multi_paths():
  """
  Returns the correct gettext translations that should be used for this
  request. This will never fail and return a dummy translation object
  if used outside of the request or if a translation cannot be found.
  """
  ctx = _request_ctx_stack.top
  if ctx is None:
      return None

  translations = getattr(ctx, 'babel_translations', None)
  if translations is None:
    babel_ext = ctx.app.extensions['babel']
    translations = None
    trs = None

    # reverse order: thus the application catalog is loaded last, so that
    # translations from libraries can be overriden
    for (dirname, domain) in reversed(babel_ext._translations_paths):
      trs = Translations.load(dirname,
                              locales=[flask_babel.get_locale()],
                              domain=domain)

      # babel.support.Translations is a subclass of
      # babel.support.NullTranslations, so we test if object has a 'merge'
      # method

      if not trs or not hasattr(trs, 'merge'):
        # got None or NullTranslations instance
        continue
      elif (translations is not None and hasattr(translations, 'merge')):
          translations.merge(trs)
      else:
          translations = trs

    # ensure translations is at least a NullTranslations object
    if translations is None:
      translations = trs

    ctx.babel_translations = translations

  return translations

# monkey patch flask-babel
flask_babel.get_translations = _get_translations_multi_paths

#: importable instance of :class:`Babel`
babel = Babel()


def localeselector():
  """
  Default locale selector used in abilian applications
  """
  # if a user is logged in, use the locale from the user settings
  user = getattr(g, 'user', None)
  if user is not None:
    locale = getattr(user, 'locale', None)
    if locale:
      return locale

  # Otherwise, try to guess the language from the user accept header the browser
  # transmits.  By default we support en/fr. The best match wins.
  return request.accept_languages.best_match(
    current_app.config['BABEL_ACCEPT_LANGUAGES']
  )


def timezoneselector():
  """
  Default timezone selector used in abilian applications
  """
  return LOCALTZ


@contextmanager
def set_locale(locale):
  """
  Change current locale.

  Can be used as a context manager to temporary change locale::

      with set_locale('fr') as fr_locale:
          ...

  :type locale: :class:`babel.core.Locale` or `str`
  :param locale: locale to use. If it's a string if must be a valid locale
                 specification
  :rtype: :class:`babel.core.Locale`
  :return: locale set
  """
  ctx = _request_ctx_stack.top
  if ctx is None:
    yield
    return

  if not isinstance(locale, Locale):
    locale = Locale.parse(locale)

  current_locale = getattr(ctx, 'babel_locale', None)
  ctx.babel_locale = locale
  yield locale
  ctx.babel_locale = current_locale


def get_template_i18n(template_name, locale):
  """
    Build template list with preceding locale if found
  """
  if locale is None:
    return template_name

  template_list = []
  parts = template_name.rsplit('.', 1)
  root = parts[0]
  suffix = parts[1]

  if locale.territory is not None:
    locale_string = '_'.join([locale.language, locale.territory])
    localized_template_path = u'.'.join([root, locale_string, suffix])
    template_list.append(localized_template_path)

  localized_template_path = u'.'.join([root, locale.language, suffix])
  template_list.append(localized_template_path)

  # append the default
  template_list.append(template_name)
  return template_list


class ensure_request_context(object):
  """
  Context manager that ensures a request context is set up
  """
  _rq_ctx = None

  def __enter__(self):
    if _request_ctx_stack.top is None:
      ctx = self._rq_ctx = current_app.test_request_context()
      ctx.__enter__()

  def __exit__(self, *args):
    ctx = self._rq_ctx
    self._rq_ctx = None

    if ctx is not None:
      ctx.__exit__(*args)


def render_template_i18n(template_name_or_list, **context):
  """
    Try to build an ordered list of template to satisfy the current locale
  """
  template_list = []
  # Use locale if present in **context
  if 'locale' in context:
    locale = Locale.parse(context['locale'])
  else:
    # Use get_locale() or default_locale
    locale = flask_babel.get_locale()

  if isinstance(template_name_or_list, basestring):
    template_list = get_template_i18n(template_name_or_list, locale)
  else:
    # Search for locale for each member of the list, do not bypass
    for template in template_name_or_list:
        template_list.append(get_template_i18n(template, locale))

  with ensure_request_context(), set_locale(locale):
    return render_template(template_list, **context)


_NOT_WORD_RE = re.compile(r'[^\w\s]+', flags=re.UNICODE)


def to_lower_ascii(value):
  value = unicode(value)
  value = _NOT_WORD_RE.sub(u' ', value)
  value = unicodedata.normalize('NFKD', value)
  value = value.encode('ascii', 'ignore')
  value = value.decode('ascii')
  value = value.strip().lower()
  value = re.sub(r'[_\s]+', u' ', value)
  return value
