from django.db import models

from django.utils.translation import ugettext_lazy as _

SITE_CACHE = {}

class SiteManager(models.Manager):

    def get_current(self):

        """

        Returns the current ``Site`` based on the SITE_ID in the

        project's settings. The ``Site`` object is cached the first

        time it's retrieved from the database.

        """

        from django.conf import settings

        try:

            sid = settings.SITE_ID

        except AttributeError:

            from django.core.exceptions import ImproperlyConfigured

            raise ImproperlyConfigured("You're using the Django \"sites framework\" without having set the SITE_ID setting. Create a site in your database and set the SITE_ID setting to fix this error.")

        try:

            current_site = SITE_CACHE[sid]

        except KeyError:

            current_site = self.get(pk=sid)

            SITE_CACHE[sid] = current_site

        return current_site

    def clear_cache(self):

        """Clears the ``Site`` object cache."""

        global SITE_CACHE

        SITE_CACHE = {}

class Site(models.Model):

    domain = models.CharField(_('domain name'), max_length=100)

    name = models.CharField(_('display name'), max_length=50)

    objects = SiteManager()

    class Meta:

        db_table = 'django_site'

        verbose_name = _('site')

        verbose_name_plural = _('sites')

        ordering = ('domain',)

    def __unicode__(self):

        return self.domain

    def save(self, *args, **kwargs):

        super(Site, self).save(*args, **kwargs)

        # Cached information will likely be incorrect now.

        if self.id in SITE_CACHE:

            del SITE_CACHE[self.id]

    def delete(self):

        pk = self.pk

        super(Site, self).delete()

        try:

            del SITE_CACHE[pk]

        except KeyError:

            pass

class RequestSite(object):

    """

    A class that shares the primary interface of Site (i.e., it has

    ``domain`` and ``name`` attributes) but gets its data from a Django

    HttpRequest object rather than from a database.

    The save() and delete() methods raise NotImplementedError.

    """

    def __init__(self, request):

        self.domain = self.name = request.get_host()

    def __unicode__(self):

        return self.domain

    def save(self, force_insert=False, force_update=False):

        raise NotImplementedError('RequestSite cannot be saved.')

    def delete(self):

        raise NotImplementedError('RequestSite cannot be deleted.')