from django.core import urlresolvers

import urllib

PING_URL = "http://www.google.com/webmasters/tools/ping"

class SitemapNotFound(Exception):

    pass

def ping_google(sitemap_url=None, ping_url=PING_URL):

    """

    Alerts Google that the sitemap for the current site has been updated.

    If sitemap_url is provided, it should be an absolute path to the sitemap

    for this site -- e.g., '/sitemap.xml'. If sitemap_url is not provided, this

    function will attempt to deduce it by using urlresolvers.reverse().

    """

    if sitemap_url is None:

        try:

            # First, try to get the "index" sitemap URL.

            sitemap_url = urlresolvers.reverse('django.contrib.sitemaps.views.index')

        except urlresolvers.NoReverseMatch:

            try:

                # Next, try for the "global" sitemap URL.

                sitemap_url = urlresolvers.reverse('django.contrib.sitemaps.views.sitemap')

            except urlresolvers.NoReverseMatch:

                pass

    if sitemap_url is None:

        raise SitemapNotFound("You didn't provide a sitemap_url, and the sitemap URL couldn't be auto-detected.")

    from django.contrib.sites.models import Site

    current_site = Site.objects.get_current()

    url = "http://%s%s" % (current_site.domain, sitemap_url)

    params = urllib.urlencode({'sitemap':url})

    urllib.urlopen("%s?%s" % (ping_url, params))

class Sitemap:

    def __get(self, name, obj, default=None):

        try:

            attr = getattr(self, name)

        except AttributeError:

            return default

        if callable(attr):

            return attr(obj)

        return attr

    def items(self):

        return []

    def location(self, obj):

        return obj.get_absolute_url()

    def get_urls(self):

        from django.contrib.sites.models import Site

        current_site = Site.objects.get_current()

        urls = []

        for item in self.items():

            loc = "http://%s%s" % (current_site.domain, self.__get('location', item))

            url_info = {

                'location':   loc,

                'lastmod':    self.__get('lastmod', item, None),

                'changefreq': self.__get('changefreq', item, None),

                'priority':   self.__get('priority', item, None)

            }

            urls.append(url_info)

        return urls

class FlatPageSitemap(Sitemap):

    def items(self):

        from django.contrib.sites.models import Site

        current_site = Site.objects.get_current()

        return current_site.flatpage_set.all()

class GenericSitemap(Sitemap):

    priority = None

    changefreq = None

    def __init__(self, info_dict, priority=None, changefreq=None):

        self.queryset = info_dict['queryset']

        self.date_field = info_dict.get('date_field', None)

        self.priority = priority

        self.changefreq = changefreq

    def items(self):

        # Make sure to return a clone; we don't want premature evaluation.

        return self.queryset.filter()

    def lastmod(self, item):

        if self.date_field is not None:

            return getattr(item, self.date_field)

        return None