#49 Parcels and Districts

* fixes bug in GeometryConflict conflict checking
* WIP: introduces new konova/utils/wfs/spatial holding SpatialWFSFetcher, which can be fed any geometry and it returns found features
* WIP: adds tests for wfs fetching
* updates requirements.txt

konova/utils/wfs/spatial.py

@@ -0,0 +1,92 @@
+"""
+Author: Michel Peltriaux
+Organization: Struktur- und Genehmigungsdirektion Nord, Rhineland-Palatinate, Germany
+Contact: michel.peltriaux@sgdnord.rlp.de
+Created on: 17.12.21
+
+"""
+from abc import abstractmethod
+
+import requests
+import xmltodict
+from django.contrib.gis.db.models.functions import AsGML, Transform
+from django.contrib.gis.geos import MultiPolygon
+from owslib.wfs import WebFeatureService
+
+from konova.models import Geometry
+from konova.settings import DEFAULT_SRID_RLP
+
+
+class BaseWFSFetcher:
+    # base_url represents not the capabilities url but the parameter-free base url
+    base_url = ""
+    version = ""
+    wfs = None
+
+    def __init__(self, base_url: str, version: str = "1.1.0", *args, **kwargs):
+        self.base_url = base_url
+        self.version = version
+        self.wfs = WebFeatureService(
+            url=base_url,
+            version=version,
+        )
+
+    @abstractmethod
+    def get_features(self, feature_identifier: str, filter: str):
+        raise NotImplementedError
+
+
+class SpatialWFSFetcher(BaseWFSFetcher):
+    """ Fetches features from a parcel WFS
+
+    """
+    geometry = None
+    geometry_property_name = ""
+
+    def __init__(self, geometry: MultiPolygon, geometry_property_name: str = "msGeometry", *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.geometry = geometry
+        self.geometry_property_name = geometry_property_name
+
+    def _create_geometry_filter(self, geometry_operation: str, filter_srid: str = None):
+        """ Creates an
+
+        Args:
+            geometry_operation ():
+            filter_srid ():
+
+        Returns:
+
+        """
+        if filter_srid is None:
+            filter_srid = DEFAULT_SRID_RLP
+        geom_gml = Geometry.objects.filter(
+            id=self.geometry.id
+        ).annotate(
+            transformed=Transform(srid=filter_srid, expression="geom")
+        ).annotate(
+            gml=AsGML('transformed')
+        ).first().gml
+        _filter = f"<Filter><{geometry_operation}><PropertyName>{self.geometry_property_name}</PropertyName>{geom_gml}</{geometry_operation}></Filter>"
+        return _filter
+
+    def get_features(self, typenames: str, geometry_operation: str = "Intersects", filter_srid: str = None, filter: str = None):
+        if filter is None:
+            filter = self._create_geometry_filter(geometry_operation, filter_srid)
+        response = requests.post(
+            url=f"{self.base_url}?request=GetFeature&service=WFS&version={self.version}&typenames={typenames}&count=10",
+            data={
+                "filter": filter,
+            }
+        )
+        content = response.content.decode("utf-8")
+        content = xmltodict.parse(content)
+        features = content.get(
+            "wfs:FeatureCollection",
+            {},
+        ).get(
+            "gml:featureMember",
+            [],
+        )
+        return features
+