Add feature field to SnapResult (#28)

rivertopo/snapping.py

@@ -6,9 +6,9 @@
 
 ogr.UseExceptions()
 
-SnapResult = namedtuple('SnapResult', ['segment', 'param', 'offset'])
+SnapResult = namedtuple('SnapResult', ['feature', 'segment', 'chainage', 'offset'])
 
-def snap_points(points, linestring):
+def snap_points(points, feature_id, linestring):
     """
     For an array of points, find their nearest locations on a given linestring
     geometry.
@@ -55,8 +55,9 @@ def snap_points(points, linestring):
         offset = point_dists[closest_segment_index] * np.sign(np.cross(vector_rejections[closest_segment_index], linestring_vectors[closest_segment_index]))
 
         snap_results.append(SnapResult(
+            feature=feature_id,
             segment=closest_segment_index,
-            param=linestring_vector_projparams[closest_segment_index],
+            chainage=linestring_vector_projparams[closest_segment_index],
             offset=offset,
         ))
 

tests/test_snapping.py

@@ -12,20 +12,23 @@ def test_snap_points():
     linestring.AddPoint(6.0, 3.0)
     linestring.AddPoint(9.0, 7.0)
 
+    feature_id = 42
+
     points = np.array([
         [1.0, 1.0],
         [4.5, 3.5],
         [5.5, 2.5],
     ])
 
     expected_results = [
-        SnapResult(segment=0, param=0.28, offset=-0.2),
-        SnapResult(segment=1, param=0.25, offset=-0.5),
-        SnapResult(segment=1, param=0.75, offset=0.5),
+        SnapResult(feature=42, segment=0, chainage=0.28, offset=-0.2),
+        SnapResult(feature=42, segment=1, chainage=0.25, offset=-0.5),
+        SnapResult(feature=42, segment=1, chainage=0.75, offset=0.5),
     ]
 
-    snap_results = snap_points(points, linestring)
+    snap_results = snap_points(points, feature_id, linestring)
 
+    assert [actual.feature for actual in snap_results] == [expected.feature for expected in expected_results]
     assert [actual.segment for actual in snap_results] == [expected.segment for expected in expected_results]
-    assert np.allclose([actual.param for actual in snap_results], [expected.param for expected in expected_results])
-    assert np.allclose([actual.offset for actual in snap_results], [expected.offset for expected in expected_results])
+    assert np.allclose([actual.chainage for actual in snap_results], [expected.chainage for expected in expected_results])
+    assert np.allclose([actual.chainage for actual in snap_results], [expected.chainage for expected in expected_results])