Refactor coordinate processing into Polygons class

We have a bunch of stuff for doing lat/long transformation in the
`BroadcastMessage` class. This is not a good separation of concerns, now
that we have a separate class for dealing with polygons and coordinates.

app/broadcast_areas/__init__.py

@@ -1,8 +1,7 @@
-import itertools
-
 from notifications_utils.serialised_model import SerialisedModelCollection
 from werkzeug.utils import cached_property
 
+from .polygons import Polygons
 from .repo import BroadcastAreasRepository
 
 
@@ -35,11 +34,15 @@ class BroadcastArea(SortableMixin):
 
     @cached_property
     def polygons(self):
-        return BroadcastAreasRepository().get_polygons_for_area(self.id)
+        return Polygons(
+            BroadcastAreasRepository().get_polygons_for_area(self.id)
+        )
 
     @cached_property
     def simple_polygons(self):
-        return BroadcastAreasRepository().get_simple_polygons_for_area(self.id)
+        return Polygons(
+            BroadcastAreasRepository().get_simple_polygons_for_area(self.id)
+        )
 
     @property
     def sub_areas(self):
@@ -80,29 +83,5 @@ class BroadcastAreaLibraries(SerialisedModelCollection, GetItemByIdMixin):
         areas = BroadcastAreasRepository().get_areas(area_ids)
         return [BroadcastArea(area) for area in areas]
 
-    def get_polygons_for_areas_long_lat(self, *area_ids):
-        return list(itertools.chain(*(
-            area.polygons
-            for area in self.get_areas(*area_ids)
-        )))
-
-    def get_polygons_for_areas_lat_long(self, *area_ids):
-        return [
-            [[long, lat] for lat, long in polygon]
-            for polygon in self.get_polygons_for_areas_long_lat(*area_ids)
-        ]
-
-    def get_simple_polygons_for_areas_long_lat(self, *area_ids):
-        return list(itertools.chain(*(
-            area.simple_polygons
-            for area in self.get_areas(*area_ids)
-        )))
-
-    def get_simple_polygons_for_areas_lat_long(self, *area_ids):
-        return [
-            [[long, lat] for lat, long in polygon]
-            for polygon in self.get_simple_polygons_for_areas_long_lat(*area_ids)
-        ]
-
 
 broadcast_area_libraries = BroadcastAreaLibraries()

app/broadcast_areas/create-broadcast-areas-db.py

@@ -43,7 +43,10 @@ def polygons_and_simplified_polygons(feature):
             'Polygons.perimeter_to_buffer_ratio)'
         )
 
-    return full_resolution.as_coordinate_pairs, simplified.as_coordinate_pairs
+    return (
+        full_resolution.as_coordinate_pairs_long_lat,
+        simplified.as_coordinate_pairs_long_lat,
+    )
 
 
 repo = BroadcastAreasRepository()

app/broadcast_areas/polygons.py

@@ -53,6 +53,9 @@ class Polygons():
     def __getitem__(self, index):
         return self.polygons[index]
 
+    def __len__(self):
+        return len(self.polygons)
+
     @cached_property
     def perimeter_length(self):
         return sum(
@@ -141,25 +144,22 @@ class Polygons():
         ])
 
     @cached_property
-    def as_coordinate_pairs(self):
+    def as_coordinate_pairs_long_lat(self):
         return [
-            [
-                [x, y] for x, y in p.exterior.coords
-            ]
-            for p in self
+            [[x, y] for x, y in polygon.exterior.coords]
+            for polygon in self
         ]
 
     @cached_property
-    def as_unenclosed_coordinate_pairs(self):
-        # Some mapping tools require shapes to be unenclosed, i.e. the
-        # last point joins the first point implicitly
+    def as_coordinate_pairs_lat_long(self):
         return [
-            coordinates[:-1] for coordinates in self.as_coordinate_pairs
+            [[y, x] for x, y in coordinate_pairs]
+            for coordinate_pairs in self.as_coordinate_pairs_long_lat
         ]
 
     @cached_property
     def point_count(self):
-        return len(list(itertools.chain(*self.as_coordinate_pairs)))
+        return len(list(itertools.chain(*self.as_coordinate_pairs_long_lat)))
 
 
 def flatten_polygons(polygons):