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1 from django.contrib.syndication.feeds import Feed as BaseFeed, FeedDoesNotExist |
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2 from django.utils.feedgenerator import Atom1Feed, Rss201rev2Feed |
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3 |
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4 class GeoFeedMixin(object): |
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5 """ |
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6 This mixin provides the necessary routines for SyndicationFeed subclasses |
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7 to produce simple GeoRSS or W3C Geo elements. |
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8 """ |
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9 |
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10 def georss_coords(self, coords): |
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11 """ |
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12 In GeoRSS coordinate pairs are ordered by lat/lon and separated by |
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13 a single white space. Given a tuple of coordinates, this will return |
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14 a unicode GeoRSS representation. |
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15 """ |
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16 return u' '.join([u'%f %f' % (coord[1], coord[0]) for coord in coords]) |
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17 |
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18 def add_georss_point(self, handler, coords, w3c_geo=False): |
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19 """ |
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20 Adds a GeoRSS point with the given coords using the given handler. |
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21 Handles the differences between simple GeoRSS and the more pouplar |
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22 W3C Geo specification. |
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23 """ |
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24 if w3c_geo: |
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25 lon, lat = coords[:2] |
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26 handler.addQuickElement(u'geo:lat', u'%f' % lat) |
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27 handler.addQuickElement(u'geo:lon', u'%f' % lon) |
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28 else: |
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29 handler.addQuickElement(u'georss:point', self.georss_coords((coords,))) |
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30 |
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31 def add_georss_element(self, handler, item, w3c_geo=False): |
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32 """ |
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33 This routine adds a GeoRSS XML element using the given item and handler. |
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34 """ |
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35 # Getting the Geometry object. |
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36 geom = item.get('geometry', None) |
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37 if not geom is None: |
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38 if isinstance(geom, (list, tuple)): |
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39 # Special case if a tuple/list was passed in. The tuple may be |
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40 # a point or a box |
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41 box_coords = None |
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42 if isinstance(geom[0], (list, tuple)): |
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43 # Box: ( (X0, Y0), (X1, Y1) ) |
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44 if len(geom) == 2: |
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45 box_coords = geom |
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46 else: |
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47 raise ValueError('Only should be two sets of coordinates.') |
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48 else: |
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49 if len(geom) == 2: |
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50 # Point: (X, Y) |
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51 self.add_georss_point(handler, geom, w3c_geo=w3c_geo) |
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52 elif len(geom) == 4: |
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53 # Box: (X0, Y0, X1, Y1) |
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54 box_coords = (geom[:2], geom[2:]) |
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55 else: |
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56 raise ValueError('Only should be 2 or 4 numeric elements.') |
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57 # If a GeoRSS box was given via tuple. |
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58 if not box_coords is None: |
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59 if w3c_geo: raise ValueError('Cannot use simple GeoRSS box in W3C Geo feeds.') |
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60 handler.addQuickElement(u'georss:box', self.georss_coords(box_coords)) |
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61 else: |
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62 # Getting the lower-case geometry type. |
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63 gtype = str(geom.geom_type).lower() |
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64 if gtype == 'point': |
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65 self.add_georss_point(handler, geom.coords, w3c_geo=w3c_geo) |
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66 else: |
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67 if w3c_geo: raise ValueError('W3C Geo only supports Point geometries.') |
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68 # For formatting consistent w/the GeoRSS simple standard: |
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69 # http://georss.org/1.0#simple |
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70 if gtype in ('linestring', 'linearring'): |
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71 handler.addQuickElement(u'georss:line', self.georss_coords(geom.coords)) |
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72 elif gtype in ('polygon',): |
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73 # Only support the exterior ring. |
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74 handler.addQuickElement(u'georss:polygon', self.georss_coords(geom[0].coords)) |
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75 else: |
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76 raise ValueError('Geometry type "%s" not supported.' % geom.geom_type) |
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77 |
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78 ### SyndicationFeed subclasses ### |
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79 class GeoRSSFeed(Rss201rev2Feed, GeoFeedMixin): |
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80 def rss_attributes(self): |
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81 attrs = super(GeoRSSFeed, self).rss_attributes() |
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82 attrs[u'xmlns:georss'] = u'http://www.georss.org/georss' |
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83 return attrs |
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84 |
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85 def add_item_elements(self, handler, item): |
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86 super(GeoRSSFeed, self).add_item_elements(handler, item) |
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87 self.add_georss_element(handler, item) |
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88 |
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89 def add_root_elements(self, handler): |
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90 super(GeoRSSFeed, self).add_root_elements(handler) |
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91 self.add_georss_element(handler, self.feed) |
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92 |
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93 class GeoAtom1Feed(Atom1Feed, GeoFeedMixin): |
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94 def root_attributes(self): |
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95 attrs = super(GeoAtom1Feed, self).root_attributes() |
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96 attrs[u'xmlns:georss'] = u'http://www.georss.org/georss' |
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97 return attrs |
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98 |
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99 def add_item_elements(self, handler, item): |
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100 super(GeoAtom1Feed, self).add_item_elements(handler, item) |
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101 self.add_georss_element(handler, item) |
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102 |
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103 def add_root_elements(self, handler): |
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104 super(GeoAtom1Feed, self).add_root_elements(handler) |
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105 self.add_georss_element(handler, self.feed) |
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106 |
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107 class W3CGeoFeed(Rss201rev2Feed, GeoFeedMixin): |
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108 def rss_attributes(self): |
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109 attrs = super(W3CGeoFeed, self).rss_attributes() |
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110 attrs[u'xmlns:geo'] = u'http://www.w3.org/2003/01/geo/wgs84_pos#' |
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111 return attrs |
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112 |
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113 def add_item_elements(self, handler, item): |
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114 super(W3CGeoFeed, self).add_item_elements(handler, item) |
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115 self.add_georss_element(handler, item, w3c_geo=True) |
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116 |
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117 def add_root_elements(self, handler): |
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118 super(W3CGeoFeed, self).add_root_elements(handler) |
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119 self.add_georss_element(handler, self.feed, w3c_geo=True) |
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120 |
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121 ### Feed subclass ### |
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122 class Feed(BaseFeed): |
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123 """ |
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124 This is a subclass of the `Feed` from `django.contrib.syndication`. |
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125 This allows users to define a `geometry(obj)` and/or `item_geometry(item)` |
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126 methods on their own subclasses so that geo-referenced information may |
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127 placed in the feed. |
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128 """ |
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129 feed_type = GeoRSSFeed |
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130 |
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131 def feed_extra_kwargs(self, obj): |
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132 return {'geometry' : self.__get_dynamic_attr('geometry', obj)} |
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133 |
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134 def item_extra_kwargs(self, item): |
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135 return {'geometry' : self.__get_dynamic_attr('item_geometry', item)} |