Merge pull request #3565 from alphagov/polygon-overspill

Show indication of how a broadcast will overspill the selected area

app/broadcast_areas/__init__.py

@@ -138,5 +138,17 @@ class BroadcastAreaLibraries(SerialisedModelCollection, GetItemByIdMixin):
             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

@@ -4,9 +4,9 @@ from copy import deepcopy
 from pathlib import Path
 
 import geojson
+import shapely.geometry as sgeom
 from notifications_utils.safe_string import make_string_safe_for_id
 
-import shapely.geometry as sgeom
 from repo import BroadcastAreasRepository
 
 package_path = Path(__file__).resolve().parent

app/broadcast_areas/plot-areas.py

@@ -3,12 +3,12 @@
 from random import sample
 
 import geojson
+import shapely.geometry as sgeom
 from notifications_utils.safe_string import make_string_safe_for_id
 
 import cartopy.crs as ccrs
 import cartopy.feature as cfeature
 import matplotlib.pyplot as plt
-import shapely.geometry as sgeom
 from repo import BroadcastAreasRepository
 
 

app/models/broadcast_message.py

@@ -2,6 +2,8 @@ from datetime import datetime
 
 from notifications_utils.template import BroadcastPreviewTemplate
 from orderedset import OrderedSet
+from shapely.geometry import MultiPolygon, Polygon
+from shapely.ops import unary_union
 from werkzeug.utils import cached_property
 
 from app.broadcast_areas import broadcast_area_libraries
@@ -76,6 +78,25 @@ class BroadcastMessage(JSONModel):
             *self._dict['areas']
         )
 
+    @property
+    def simple_polygons(self):
+        simple_polygons = broadcast_area_libraries.get_simple_polygons_for_areas_lat_long(
+            *self._dict['areas']
+        )
+        unioned_polygons = unary_union([
+            Polygon(i) for i in simple_polygons
+        ])
+        if isinstance(unioned_polygons, MultiPolygon):
+            return [
+                [
+                    [x, y] for x, y in p.exterior.coords
+                ]
+                for p in unioned_polygons
+            ]
+        return [[
+            [x, y] for x, y in unioned_polygons.exterior.coords
+        ]]
+
     @property
     def template(self):
         response = service_api_client.get_service_template(

app/templates/views/broadcast/preview-areas.html

@@ -36,12 +36,23 @@
       attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'
     }).addTo(mymap);
 
+    {% for polygon in broadcast_message.simple_polygons %}
+      polygons.push(
+        L.polygon({{polygon}}, {
+          color: '#2B8CC4', // $light-blue
+          opacity: 0.4,
+          fillColor: '#2B8CC4', // $light-blue
+          fillOpacity: 0.3,
+          weight: 1
+        })
+      );
+    {% endfor %}
+
     {% for polygon in broadcast_message.polygons %}
       polygons.push(
         L.polygon({{polygon}}, {
           color: '#0b0b0c', // $black
-          fillColor: '#2B8CC4', // $light-blue
-          fillOpacity: 0.2,
+          fillOpacity: 0,
           weight: 2
         })
       );

requirements-app.txt

@@ -18,6 +18,7 @@ pytz==2020.1
 gunicorn==20.0.4
 eventlet==0.26.1
 notifications-python-client==5.7.0
+Shapely==1.7.0
 
 # PaaS
 awscli-cwlogs>=1.4,<1.5

requirements.txt

@@ -20,6 +20,7 @@ pytz==2020.1
 gunicorn==20.0.4
 eventlet==0.26.1
 notifications-python-client==5.7.0
+Shapely==1.7.0
 
 # PaaS
 awscli-cwlogs>=1.4,<1.5

tests/__init__.py

@@ -649,6 +649,7 @@ def broadcast_message_json(
     cancelled_at=None,
     approved_by_id=None,
     cancelled_by_id=None,
+    areas=None,
 ):
     return {
         'id': id_,
@@ -660,7 +661,7 @@ def broadcast_message_json(
         'template_name': 'Example template',
 
         'personalisation': {},
-        'areas': [
+        'areas': areas or [
             'countries-E92000001', 'countries-S92000003',
         ],
 

tests/app/models/test_broadcast_message.py

@@ -0,0 +1,30 @@
+from app.models.broadcast_message import BroadcastMessage
+from tests import broadcast_message_json
+
+
+def test_simple_polygons(fake_uuid):
+    broadcast_message = BroadcastMessage(broadcast_message_json(
+        id_=fake_uuid,
+        service_id=fake_uuid,
+        template_id=fake_uuid,
+        status='draft',
+        created_by_id=fake_uuid,
+        areas=[
+            # Hackney Central
+            'electoral-wards-of-the-united-kingdom-E05009372',
+            # Hackney Wick
+            'electoral-wards-of-the-united-kingdom-E05009374',
+        ],
+    ))
+
+    assert [
+        [len(polygon) for polygon in broadcast_message.polygons],
+        [len(polygon) for polygon in broadcast_message.simple_polygons],
+    ] == [
+        # One polygon for each area
+        [27, 31],
+        # Because the areas are close to each other, the simplification
+        # and unioning process results in a single polygon with fewer
+        # total coordinates
+        [34],
+    ]