Better blending of adjacent lines on map

front/map.js

@@ -1,5 +1,6 @@
 require('ol/ol.css');
 
+const axios = require('axios');
 const {Map, View} = require('ol');
 
 const TileLayer = require('ol/layer/Tile').default;
@@ -17,47 +18,77 @@ const proj = require('ol/proj');
 const {Style, Fill, Stroke, Circle} = require('ol/style');
 const color = require('color');
 
-const mapboxToken = 'pk.eyJ1IjoibWF0dGVvZGVsYWJyZSIsImEiOiJjazUxaWNsdXcwdWhjM2\
-9tc2xndXJoNGtxIn0.xELwMerqJLFimIqU6RxnZw';
+const mapboxToken = `pk.eyJ1IjoibWF0dGVvZGVsYWJyZSIsImEiOiJja2NxaTUyMmUwcmFhMn\
+h0NmFsdzQ3emxqIn0.cyxF0h36emIMTk3cc4VqUw`;
 
 const server = window.origin;
 
 const fetchDataSources = async () =>
 {
-    const dataSource = new VectorSource();
+    const segmentsSource = new VectorSource();
+    const stopsSource = new VectorSource();
 
-    const res = await fetch(`${server}/network`);
-    const network = await res.json();
+    const network = (await axios.get(`${server}/network`)).data;
 
-    const stopPoints = Object.entries(network.stops)
-        .map(([stopId, stop]) =>
-            new Feature({
-                type: 'stop',
-                color: network.lines[stop.lines[0]].color,
-                geometry: new Point(proj.fromLonLat([stop.lon, stop.lat])),
-            })
-        );
-
-    dataSource.addFeatures(stopPoints);
-
-    const segmentLines = Object.values(network.lines)
-        .flatMap(({color, routes}) =>
+    segmentsSource.addFeatures(
+        Object.values(network.lines).flatMap(({color, routes}) =>
             routes.map(({segments}) =>
                 new Feature({
-                    type: 'segment',
                     color,
                     geometry: new LineString(segments.flat().map(
                         ({lat, lon}) => proj.fromLonLat([lon, lat])
                     )),
                 })
             )
-        );
+        )
+    );
 
-    dataSource.addFeatures(segmentLines);
+    stopsSource.addFeatures(
+        Object.entries(network.stops).map(([stopId, stop]) =>
+            new Feature({
+                color: network.lines[stop.lines[0]].color,
+                geometry: new Point(proj.fromLonLat([stop.lon, stop.lat])),
+            })
+        )
+    );
 
-    return dataSource;
+    return {segmentsSource, stopsSource};
 };
 
+const makeBorderColor = mainColor =>
+{
+    const hsl = color(mainColor).hsl();
+    hsl.color = Math.max(0, hsl.color[2] -= 20);
+    return hsl.hex();
+};
+
+const segmentsBorderStyle = feature => new Style({
+    stroke: new Stroke({
+        color: makeBorderColor(feature.get('color')),
+        width: 8,
+    }),
+});
+
+const segmentsInnerStyle = feature => new Style({
+    stroke: new Stroke({
+        color: feature.get('color'),
+        width: 6,
+    }),
+});
+
+const stopsStyle = feature => new Style({
+    image: new Circle({
+        fill: new Fill({
+            color: feature.get('color'),
+        }),
+        stroke: new Stroke({
+            color: makeBorderColor(feature.get('color')),
+            width: 1.5,
+        }),
+        radius: 6,
+    }),
+});
+
 const createMap = async (target) =>
 {
     // Map background
@@ -74,54 +105,31 @@ const createMap = async (target) =>
     });
 
     // Data overlay
-    const dataSource = await fetchDataSources();
+    const {segmentsSource, stopsSource} = await fetchDataSources();
 
-    const makeBorderColor = mainColor =>
-    {
-        const hsl = color(mainColor).hsl();
-        hsl.color = Math.max(0, hsl.color[2] -= 20);
-        return hsl.hex();
-    };
+    const segmentsBorderLayer = new VectorLayer({
+        source: segmentsSource,
+        style: segmentsBorderStyle,
 
-    const dataLayer = new VectorLayer({
-        source: dataSource,
         updateWhileInteracting: true,
         updateWhileAnimating: true,
-        style: feature =>
-        {
-            if (feature.get('type') === 'stop')
-            {
-                return new Style({
-                    image: new Circle({
-                        fill: new Fill({
-                            color: feature.get('color'),
-                        }),
-                        stroke: new Stroke({
-                            color: makeBorderColor(feature.get('color')),
-                            width: 2,
-                        }),
-                        radius: 6,
-                    }),
-                });
-            }
-            else if (feature.get('type') === 'segment')
-            {
-                return [
-                    new Style({
-                        stroke: new Stroke({
-                            color: makeBorderColor(feature.get('color')),
-                            width: 8,
-                        }),
-                    }),
-                    new Style({
-                        stroke: new Stroke({
-                            color: feature.get('color'),
-                            width: 6,
-                        }),
-                    }),
-                ];
-            }
-        },
+    });
+
+    const segmentsInnerLayer = new VectorLayer({
+        source: segmentsSource,
+        style: segmentsInnerStyle,
+
+        updateWhileInteracting: true,
+        updateWhileAnimating: true,
+    });
+
+    const stopsLayer = new VectorLayer({
+        source: stopsSource,
+        style: stopsStyle,
+
+        minZoom: 13,
+        updateWhileInteracting: true,
+        updateWhileAnimating: true,
     });
 
     // Setup map
@@ -129,7 +137,9 @@ const createMap = async (target) =>
         target,
         layers: [
             backgroundLayer,
-            dataLayer,
+            segmentsBorderLayer,
+            segmentsInnerLayer,
+            stopsLayer,
         ],
         view: new View({
             center: proj.fromLonLat([3.88, 43.605]),