import asyncio
from speaklater import is_lazy_string, make_lazy_string
from aiohttp_babel import locale
from babel.core import UnknownLocaleError
from threading import local

_thread_locals = local()


def make_lazy_gettext(lookup_func):
    def lazy_gettext(string, *args, **kwargs):
        if is_lazy_string(string):
            return string
        return make_lazy_string(lookup_func(), string, *args, **kwargs)
    return lazy_gettext

_ = make_lazy_gettext(lambda: _thread_locals.locale.translate)


@asyncio.coroutine
def babel_middleware(app, handler):
    @asyncio.coroutine
    def middleware(request):
        # get locale from cookie
        _code = request.cookies.get('locale', False)
        if not _code:
            # get locale from browser
            locale_code = request.headers.get('ACCEPT-LANGUAGE', 'en')[:2]
            try:
                _code = str(locale.Locale.parse(locale_code, sep='-'))
            except (ValueError, UnknownLocaleError):
                pass

        _locale = locale.get(_code)
        _thread_locals.locale = request.locale = _locale
        response = yield from handler(request)
        return response
    return middleware


def get_current_locale():
    return getattr(_thread_locals, 'locale', None)