basic implementation

sorted test

requirements.txt

@@ -1,5 +1,6 @@
 django>=4
 django-computedfields
+fiona
 psycopg2-binary
 transifex-client
 djangorestframework

src/django_oapif/decorators.py

@@ -1,11 +1,12 @@
 from typing import Any, Callable, Dict, Optional
 
 from django.db.models import Model
-from rest_framework import viewsets
+from rest_framework import renderers, viewsets
 from rest_framework_gis.serializers import GeoFeatureModelSerializer
 
 from django_oapif.metadata import OAPIFMetadata
 from django_oapif.mixins import OAPIFDescribeModelViewSetMixin
+from django_oapif.renderers import FGBRenderer
 from django_oapif.urls import oapif_router
 
 from .filters import BboxFilterBackend
@@ -57,6 +58,7 @@ class Meta:
  else:
  """
  viewset_serializer_class = AutoSerializer
+ viewset_renderer_classes = [renderers.JSONRenderer, FGBRenderer]
  viewset_oapif_geom_lookup = (
  "geom" # one day this will be retrieved automatically from the serializer
  )
@@ -65,6 +67,7 @@ class Meta:
  class Viewset(OAPIFDescribeModelViewSetMixin, viewsets.ModelViewSet):
  queryset = Model.objects.all()
  serializer_class = viewset_serializer_class
+ renderer_classes = viewset_renderer_classes
 
  # TODO: these should probably be moved to the mixin
  oapif_title = Model._meta.verbose_name

src/django_oapif/renderers.py

@@ -0,0 +1,29 @@
+import io
+from typing import OrderedDict
+
+import fiona
+from django.http import StreamingHttpResponse
+from rest_framework import renderers
+
+
+class FGBRenderer(renderers.BaseRenderer):
+ format = "fgb"
+ media_type = "application/octet-stream"
+ # FIXME: This should be sent by the model.
+ schema = {"geometry": "Point", "properties": {"name": "str", "_serialized": "str"}}
+
+ def render(
+ self, data: OrderedDict, accepted_media_type=None, renderer_context=None
+ ) -> StreamingHttpResponse:
+ """Renders pre-serialized Python objects as a flatgeobuf binary stream"""
+ features = (fiona.Feature.from_dict(obj) for obj in data["features"])
+ buffer_wrapper = io.BytesIO()
+
+ with fiona.open(
+ buffer_wrapper, mode="w", driver="FlatGeobuf", schema=self.schema
+ ) as fh:
+ for feature in features:
+ fh.write(feature)
+
+ buffer_wrapper.seek(0)
+ return StreamingHttpResponse(buffer_wrapper)

src/signalo/core/tests.py

@@ -1,14 +1,18 @@
 import cProfile
+import io
 import logging
 import os
 import pstats
 from itertools import islice
+from operator import itemgetter
 from typing import Callable, Iterable, Tuple
 
+import fiona
 from django.contrib.auth.models import User
 from django.core.management import call_command
 from rest_framework.test import APITestCase
 
+from django_oapif.renderers import FGBRenderer
 from signalo.core.views import PoleSerializer
 
 from .models import Azimuth, Pole, Sign
@@ -189,3 +193,47 @@ def test_admin_items_options(self):
 
  self.assertEqual(allowed_body, expected)
  self.assertEqual(allowed_headers, allowed_body)
+
+
+class TestRenderers(APITestCase):
+ @classmethod
+ def setUpTestData(cls):
+ call_command("populate_vl")
+ call_command("populate_signs_poles")
+
+ cls.collection_url = collections_url + "/signalo_core.pole"
+ cls.items_url = cls.collection_url + "/items"
+
+ def test_flatgeobuf(self):
+ json_features = self.client.get(self.items_url, {"format": "json"}).json()[
+ "features"
+ ]
+ json_coordinates = [
+ tuple(json_feature["geometry"]["coordinates"])
+ for json_feature in json_features
+ ]
+ output_stream = io.BytesIO(
+ self.client.get(self.items_url, {"format": "fgb"}, streaming=True).content
+ )
+
+ with fiona.open(
+ output_stream, mode="r", driver="FlatGeobuf", schema=FGBRenderer.schema
+ ) as fgb_features:
+ fgb_coordinates = [
+ fgb_feature.geometry["coordinates"] for fgb_feature in fgb_features
+ ]
+
+ self.assertEqual(
+ set(fgb_coordinates),
+ set(json_coordinates),
+ msg="The two sources map to the same set of coordinates.",
+ )
+
+ fgb_coordinates.sort(key=itemgetter(0, 1))
+ json_coordinates.sort(key=itemgetter(0, 1))
+
+ self.assertEqual(
+ fgb_coordinates,
+ json_coordinates,
+ msg="Once sorted, the two sources map to the same list of coordinates.",
+ )