from django.contrib.syndication.views import Feed as BaseFeed
from django.utils.feedgenerator import Atom1Feed, Rss201rev2Feed
class GeoFeedMixin:
"""
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, return a string
GeoRSS representation.
"""
return " ".join("%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 popular
W3C Geo specification.
"""
if w3c_geo:
lon, lat = coords[:2]
handler.addQuickElement("geo:lat", "%f" % lat)
handler.addQuickElement("geo:lon", "%f" % lon)
else:
handler.addQuickElement("georss:point", self.georss_coords((coords,)))
def add_georss_element(self, handler, item, w3c_geo=False):
"""Add a GeoRSS XML element using the given item and handler."""
# Getting the Geometry object.
geom = item.get("geometry")
if geom is not 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 box_coords is not None:
if w3c_geo:
raise ValueError(
"Cannot use simple GeoRSS box in W3C Geo feeds."
)
handler.addQuickElement(
"georss:box", self.georss_coords(box_coords)
)
else:
# Getting the lowercase 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(
"georss:line", self.georss_coords(geom.coords)
)
elif gtype in ("polygon",):
# Only support the exterior ring.
handler.addQuickElement(
"georss:polygon", self.georss_coords(geom[0].coords)
)
else:
raise ValueError(
'Geometry type "%s" not supported.' % geom.geom_type
)
# ### SyndicationFeed subclasses ###
[docs]
class GeoRSSFeed(Rss201rev2Feed, GeoFeedMixin):
def rss_attributes(self):
attrs = super().rss_attributes()
attrs["xmlns:georss"] = "http://www.georss.org/georss"
return attrs
def add_item_elements(self, handler, item):
super().add_item_elements(handler, item)
self.add_georss_element(handler, item)
def add_root_elements(self, handler):
super().add_root_elements(handler)
self.add_georss_element(handler, self.feed)
[docs]
class GeoAtom1Feed(Atom1Feed, GeoFeedMixin):
def root_attributes(self):
attrs = super().root_attributes()
attrs["xmlns:georss"] = "http://www.georss.org/georss"
return attrs
def add_item_elements(self, handler, item):
super().add_item_elements(handler, item)
self.add_georss_element(handler, item)
def add_root_elements(self, handler):
super().add_root_elements(handler)
self.add_georss_element(handler, self.feed)
[docs]
class W3CGeoFeed(Rss201rev2Feed, GeoFeedMixin):
def rss_attributes(self):
attrs = super().rss_attributes()
attrs["xmlns:geo"] = "http://www.w3.org/2003/01/geo/wgs84_pos#"
return attrs
def add_item_elements(self, handler, item):
super().add_item_elements(handler, item)
self.add_georss_element(handler, item, w3c_geo=True)
def add_root_elements(self, handler):
super().add_root_elements(handler)
self.add_georss_element(handler, self.feed, w3c_geo=True)
# ### Feed subclass ###
[docs]
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)}
Sep 29, 2023