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from django.contrib.syndication.feeds import Feed as BaseFeed, FeedDoesNotExist
from django.utils.feedgenerator import Atom1Feed, Rss201rev2Feed
class GeoFeedMixin(object):
"""
This mixin provides the necessary routines for SyndicationFeed subclasses
to produce simple GeoRSS or W3C Geo elements.
"""
def georss_coords(self, coords):
"""
In GeoRSS coordinate pairs are ordered by lat/lon and separated by
a single white space. Given a tuple of coordinates, this will return
a unicode GeoRSS representation.
"""
return u' '.join([u'%f %f' % (coord[1], coord[0]) for coord in coords])
def add_georss_point(self, handler, coords, w3c_geo=False):
"""
Adds a GeoRSS point with the given coords using the given handler.
Handles the differences between simple GeoRSS and the more pouplar
W3C Geo specification.
"""
if w3c_geo:
lon, lat = coords[:2]
handler.addQuickElement(u'geo:lat', u'%f' % lat)
handler.addQuickElement(u'geo:lon', u'%f' % lon)
else:
handler.addQuickElement(u'georss:point', self.georss_coords((coords,)))
def add_georss_element(self, handler, item, w3c_geo=False):
"""
This routine adds a GeoRSS XML element using the given item and handler.
"""
# Getting the Geometry object.
geom = item.get('geometry', None)
if not geom is None:
if isinstance(geom, (list, tuple)):
# Special case if a tuple/list was passed in. The tuple may be
# a point or a box
box_coords = None
if isinstance(geom[0], (list, tuple)):
# Box: ( (X0, Y0), (X1, Y1) )
if len(geom) == 2:
box_coords = geom
else:
raise ValueError('Only should be two sets of coordinates.')
else:
if len(geom) == 2:
# Point: (X, Y)
self.add_georss_point(handler, geom, w3c_geo=w3c_geo)
elif len(geom) == 4:
# Box: (X0, Y0, X1, Y1)
box_coords = (geom[:2], geom[2:])
else:
raise ValueError('Only should be 2 or 4 numeric elements.')
# If a GeoRSS box was given via tuple.
if not box_coords is None:
if w3c_geo: raise ValueError('Cannot use simple GeoRSS box in W3C Geo feeds.')
handler.addQuickElement(u'georss:box', self.georss_coords(box_coords))
else:
# Getting the lower-case geometry type.
gtype = str(geom.geom_type).lower()
if gtype == 'point':
self.add_georss_point(handler, geom.coords, w3c_geo=w3c_geo)
else:
if w3c_geo: raise ValueError('W3C Geo only supports Point geometries.')
# For formatting consistent w/the GeoRSS simple standard:
# http://georss.org/1.0#simple
if gtype in ('linestring', 'linearring'):
handler.addQuickElement(u'georss:line', self.georss_coords(geom.coords))
elif gtype in ('polygon',):
# Only support the exterior ring.
handler.addQuickElement(u'georss:polygon', self.georss_coords(geom[0].coords))
else:
raise ValueError('Geometry type "%s" not supported.' % geom.geom_type)
### SyndicationFeed subclasses ###
class GeoRSSFeed(Rss201rev2Feed, GeoFeedMixin):
def rss_attributes(self):
attrs = super(GeoRSSFeed, self).rss_attributes()
attrs[u'xmlns:georss'] = u'http://www.georss.org/georss'
return attrs
def add_item_elements(self, handler, item):
super(GeoRSSFeed, self).add_item_elements(handler, item)
self.add_georss_element(handler, item)
def add_root_elements(self, handler):
super(GeoRSSFeed, self).add_root_elements(handler)
self.add_georss_element(handler, self.feed)
class GeoAtom1Feed(Atom1Feed, GeoFeedMixin):
def root_attributes(self):
attrs = super(GeoAtom1Feed, self).root_attributes()
attrs[u'xmlns:georss'] = u'http://www.georss.org/georss'
return attrs
def add_item_elements(self, handler, item):
super(GeoAtom1Feed, self).add_item_elements(handler, item)
self.add_georss_element(handler, item)
def add_root_elements(self, handler):
super(GeoAtom1Feed, self).add_root_elements(handler)
self.add_georss_element(handler, self.feed)
class W3CGeoFeed(Rss201rev2Feed, GeoFeedMixin):
def rss_attributes(self):
attrs = super(W3CGeoFeed, self).rss_attributes()
attrs[u'xmlns:geo'] = u'http://www.w3.org/2003/01/geo/wgs84_pos#'
return attrs
def add_item_elements(self, handler, item):
super(W3CGeoFeed, self).add_item_elements(handler, item)
self.add_georss_element(handler, item, w3c_geo=True)
def add_root_elements(self, handler):
super(W3CGeoFeed, self).add_root_elements(handler)
self.add_georss_element(handler, self.feed, w3c_geo=True)
### Feed subclass ###
class Feed(BaseFeed):
"""
This is a subclass of the `Feed` from `django.contrib.syndication`.
This allows users to define a `geometry(obj)` and/or `item_geometry(item)`
methods on their own subclasses so that geo-referenced information may
placed in the feed.
"""
feed_type = GeoRSSFeed
def feed_extra_kwargs(self, obj):
return {'geometry' : self.__get_dynamic_attr('geometry', obj)}
def item_extra_kwargs(self, item):
return {'geometry' : self.__get_dynamic_attr('item_geometry', item)}
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