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