Add a filter on reference points to filter based on distance

api/views.py

@@ -1,6 +1,7 @@
 from rest_framework import viewsets
+from django.conf import settings
 
-from panorama.models import Panorama, ReferencePoint, Reference
+from panorama.models import Point, Panorama, ReferencePoint, Reference
 from .serializers import *
 
 
@@ -8,6 +9,37 @@ class ReferencePointViewSet(viewsets.ModelViewSet):
     queryset = ReferencePoint.objects.all()
     serializer_class = ReferencePointSerializer
 
+    def get_queryset(self):
+        """
+        Allow to filter reference points, by only considering those in a
+        disc around a given geographic position.
+
+        Example filter:
+
+            /api/v1/refpoints/?lat=42&lon=42&dist=10000
+
+        returns all reference points around (42°, 42°) at less than 10
+        kilometers.
+        """
+        queryset = ReferencePoint.objects.all()
+        lat = self.request.QUERY_PARAMS.get('lat', None)
+        lon = self.request.QUERY_PARAMS.get('lon', None)
+        # In meters
+        distance = self.request.QUERY_PARAMS.get('dist', None)
+        if distance is not None:
+            distance = int(distance)
+        else:
+            distance = settings.PANORAMA_MAX_DISTANCE
+        if lat is not None and lon is not None:
+            p = Point(float(lat), float(lon), 0)
+            # Filter refpoints based on their (great circle) distance to
+            # the parameter point.  The database can't do it, so we load
+            # all objects and filter them in Python.
+            refpoints = [refpoint.id for refpoint in ReferencePoint.objects.all()
+                         if p.great_circle_distance(refpoint) <= distance]
+            queryset = queryset.filter(id__in=refpoints)
+        return queryset
+
 
 class PanoramaViewSet(viewsets.ModelViewSet):
     queryset = Panorama.objects.all()