Simplify polygons before storing them

We’re going to let people pass in fairly complex polygons, but:
- we don’t want to store massive polygons
- we don’t want to pass the CBCs massive polygons

So this commit adds a step to simplify the polygons before storing them.

We think it’s best for us to do this because:
- writing code to do polygon simplification is non-trivial, and we don’t
  want to make all potential integrators do it
- the simplification we’ve developed is domain-specific to emergency
  alerting, so should throw away less information than

There’s a bit more detail about how we simplify polygons in
https://github.com/alphagov/notifications-admin/pull/3590/files

app/v2/broadcast/post_broadcast.py

@@ -1,5 +1,6 @@
 from itertools import chain
 from flask import jsonify, request
+from notifications_utils.polygons import Polygons
 from app import authenticated_service, api_user
 from app.broadcast_message.translators import cap_xml_to_dict
 from app.dao.dao_utils import dao_save_object
@@ -38,6 +39,10 @@ def create_broadcast():
 
     validate(broadcast_json, post_broadcast_schema)
 
+    polygons = Polygons(list(chain.from_iterable((
+        area['polygons'] for area in broadcast_json['areas']
+    ))))
+
     broadcast_message = BroadcastMessage(
         service_id=authenticated_service.id,
         content=broadcast_json['content'],
@@ -46,9 +51,7 @@ def create_broadcast():
             'areas': [
                 area['name'] for area in broadcast_json['areas']
             ],
-            'simple_polygons': list(chain.from_iterable((
+            'simple_polygons': polygons.smooth.simplify.as_coordinate_pairs_long_lat,
-                area['polygons'] for area in broadcast_json['areas']
-            )))
         },
         status=BroadcastStatusType.PENDING_APPROVAL,
         api_key_id=api_user.id,

requirements-app.txt

@@ -31,7 +31,7 @@ notifications-python-client==5.7.1
 # PaaS
 awscli-cwlogs==1.4.6
 
-git+https://github.com/alphagov/notifications-utils.git@43.5.9#egg=notifications-utils==43.5.9
+git+https://github.com/alphagov/notifications-utils.git@43.8.0#egg=notifications-utils==43.8.0
 
 # gds-metrics requires prometheseus 0.2.0, override that requirement as 0.7.1 brings significant performance gains
 prometheus-client==0.9.0

requirements.txt

@@ -33,25 +33,25 @@ notifications-python-client==5.7.1
 # PaaS
 awscli-cwlogs==1.4.6
 
-git+https://github.com/alphagov/notifications-utils.git@43.5.9#egg=notifications-utils==43.5.9
+git+https://github.com/alphagov/notifications-utils.git@43.8.0#egg=notifications-utils==43.8.0
 
 # gds-metrics requires prometheseus 0.2.0, override that requirement as 0.7.1 brings significant performance gains
 prometheus-client==0.9.0
 gds-metrics==0.2.4
 
 ## The following requirements were added by pip freeze:
-alembic==1.5.0
+alembic==1.5.2
 amqp==1.4.9
 anyjson==0.3.3
 attrs==20.3.0
-awscli==1.18.216
+awscli==1.18.219
 bcrypt==3.2.0
 billiard==3.3.0.23
 bleach==3.2.1
 blinker==1.4
 boto==2.49.0
-boto3==1.16.56
+boto3==1.16.59
-botocore==1.19.56
+botocore==1.19.59
 certifi==2020.12.5
 chardet==4.0.0
 click==7.1.2
@@ -89,6 +89,7 @@ redis==3.5.3
 requests==2.25.1
 rsa==4.5
 s3transfer==0.3.4
+Shapely==1.7.1
 six==1.15.0
 smartypants==2.0.1
 soupsieve==2.1

tests/app/v2/broadcast/test_post_broadcast.py

@@ -36,9 +36,14 @@ def test_valid_post_broadcast_returns_201(
             'category': 'Other',
             'areas': [
                 {
-                    'name': 'Borchester Downs',
+                    'name': 'Hackney Marshes',
                     'polygons': [[
-                        [1, 2], [3, 4], [5, 6], [1, 2],
+                        [-0.038280487060546875, 51.55738264619775],
+                        [-0.03184318542480469, 51.553913882566754],
+                        [-0.023174285888671875, 51.55812972989382],
+                        [-0.023174285888671999, 51.55812972989999],
+                        [-0.029869079589843747, 51.56165153059717],
+                        [-0.038280487060546875, 51.55738264619775],
                     ]],
                 },
             ],
@@ -53,7 +58,7 @@ def test_valid_post_broadcast_returns_201(
     assert response_json['approved_at'] is None
     assert response_json['approved_by_id'] == None
     assert response_json['areas'] == [
-        'Borchester Downs'
+        'Hackney Marshes'
     ]
     assert response_json['cancelled_at'] == None
     assert response_json['cancelled_by_id'] == None
@@ -65,9 +70,21 @@ def test_valid_post_broadcast_returns_201(
     assert response_json['id'] == ANY
     assert response_json['personalisation'] is None
     assert response_json['service_id'] == str(sample_broadcast_service.id)
-    assert response_json['simple_polygons'] == [
+    assert response_json['simple_polygons'] == [[
-        [[1, 2], [3, 4], [5, 6], [1, 2],]
+        [-0.03817522145265898, 51.557381351011166],
-    ]
+        [-0.03791399800364216, 51.55758039392131],
+        [-0.030362635618559567, 51.56141279571522],
+        [-0.02986997783677049, 51.56152875195115],
+        [-0.029379069367567606, 51.561405599957745],
+        [-0.023537043373602105, 51.5583323982824],
+        [-0.02328416546450603, 51.55813395976017],
+        [-0.02355422144186266, 51.557933308587664],
+        [-0.0313493058222969, 51.55414241384808],
+        [-0.031840673207720764, 51.55403463730992],
+        [-0.032327132941933706, 51.55416275685022],
+        [-0.037918974384948616, 51.55717594115094],
+        [-0.03817522145265898, 51.557381351011166],
+    ]]
     assert response_json['starts_at'] is None
     assert response_json['status'] == 'pending-approval'
     assert response_json['template_id'] is None
@@ -113,9 +130,9 @@ def test_valid_post_cap_xml_broadcast_returns_201(
     assert response_json['personalisation'] is None
     assert response_json['service_id'] == str(sample_broadcast_service.id)
     assert len(response_json['simple_polygons']) == 1
-    assert len(response_json['simple_polygons'][0]) == 29
+    assert len(response_json['simple_polygons'][0]) == 23
-    assert response_json['simple_polygons'][0][0] == [53.10569, 0.24453]
+    assert response_json['simple_polygons'][0][0] == [53.10561946699971, 0.2441253049430708]
-    assert response_json['simple_polygons'][0][-1] == [53.10569, 0.24453]
+    assert response_json['simple_polygons'][0][-1] == [53.10561946699971, 0.2441253049430708]
     assert response_json['starts_at'] is None
     assert response_json['status'] == 'pending-approval'
     assert response_json['template_id'] is None