Extend /node/ endpoint to add optional centreline conflation service

backend/app/get_nearest_centreline_node.py

@@ -0,0 +1,48 @@
+from app.db import getConnection
+from json import loads as loadJSON
+
+SQL = '''
+WITH nearest_centreline AS (
+    SELECT
+        intersection_id,
+        geom::geography <-> ST_MakePoint(%(longitude)s, %(latitude)s)::geography AS distance
+    FROM gis_core.intersection_latest
+    ORDER BY geom <-> ST_SetSRID(ST_MakePoint(%(longitude)s, %(latitude)s), 4326) ASC
+    LIMIT 1
+)
+
+SELECT
+    intersection_id AS centreline_id,
+    ST_AsGeoJSON(geom) AS geojson,
+    distance,
+    ARRAY_AGG(DISTINCT linear_name_full_from) AS street_names
+FROM nearest_centreline
+JOIN gis_core.intersection_latest AS ci USING (intersection_id)
+GROUP BY
+    intersection_id,
+    geom,
+    distance
+'''
+
+def get_nearest_centreline_node(longitude, latitude):
+    """
+    Return the nearest node from the latest city centreline network
+
+    arguments:
+    longitude (float): longitude of the point to search around
+    latitude (float): latitude of the point to search around
+    """
+    node = {}
+    with getConnection() as connection:
+        with connection.cursor() as cursor:
+            cursor.execute(SQL, {'longitude': longitude, 'latitude': latitude})
+            centreline_id, geojson, distance, street_names = cursor.fetchone()
+            node = {
+                'centreline_id': centreline_id,
+                'street_names': street_names,
+                'geometry': loadJSON(geojson),
+                'distance': distance
+            }
+    connection.close()
+    return node
+

backend/app/get_node.py

@@ -2,6 +2,7 @@
 
 import json
 from app.db import getConnection
+from app.get_nearest_centreline_node import get_nearest_centreline_node
 
 SQL = '''
 SELECT
@@ -17,7 +18,7 @@
     here_nodes.geom;
 '''
 
-def get_node(node_id):
+def get_node(node_id, conflate_with_centreline=False):
     node = {}
     with getConnection() as connection:
         with connection.cursor() as cursor:
@@ -28,5 +29,11 @@ def get_node(node_id):
                 'street_names': street_names,
                 'geometry': json.loads(geojson)
             }
+            if conflate_with_centreline:
+                lon = node['geometry']['coordinates'][0]
+                lat = node['geometry']['coordinates'][1]
+                node['conflated'] = {
+                    'centreline': get_nearest_centreline_node(lon, lat)
+                }
     connection.close()
     return node

backend/app/routes.py

@@ -1,6 +1,6 @@
 import json, re
 from datetime import datetime
-from flask import jsonify
+from flask import jsonify, request
 from app import app
 from app.db import getConnection
 from app.get_closest_nodes import get_nodes_within
@@ -54,12 +54,18 @@ def node(node_id):
 
     arguments:
     node_id (int): identifier of the node in the latest Here map version
+    optional GET arg ?doConflation will also return the nearest node in the centreline network
     """
     try:
         node_id = int(node_id)
     except:
         return jsonify({'error': "node_id should be an integer"})
-    return jsonify(get_node(node_id))
+
+    doConflation = False
+    if request.args.get('doConflation') is not None:
+        doConflation = True
+
+    return jsonify(get_node(node_id, doConflation))
 
 # test URL /link-nodes/30421154/30421153
 #shell function - outputs json for use on frontend