From de199fa668b61ca1def0b8d18de8d666d8148361 Mon Sep 17 00:00:00 2001
From: Anton Tananaev <anton.tananaev@gmail.com>
Date: Sat, 26 Jun 2021 18:25:45 -0700
Subject: Implement map clustering

---
 modern/src/map/Map.js          |  3 ++-
 modern/src/map/PositionsMap.js | 48 +++++++++++++++++++++++++++++++++++++-----
 modern/src/map/mapUtil.js      | 14 ++++++------
 3 files changed, 53 insertions(+), 12 deletions(-)

diff --git a/modern/src/map/Map.js b/modern/src/map/Map.js
index 8a43e97b..014268cd 100644
--- a/modern/src/map/Map.js
+++ b/modern/src/map/Map.js
@@ -37,9 +37,10 @@ const updateReadyValue = value => {
 
 const initMap = async () => {
   const background = await loadImage('images/background.svg');
+  map.addImage('background', await loadIcon(background), { pixelRatio: window.devicePixelRatio });
   await Promise.all(deviceCategories.map(async category => {
     if (!map.hasImage(category)) {
-      const imageData = await loadIcon(category, background, `images/icon/${category}.svg`);
+      const imageData = await loadIcon(background, `images/icon/${category}.svg`);
       map.addImage(category, imageData, { pixelRatio: window.devicePixelRatio });
     }
   }));
diff --git a/modern/src/map/PositionsMap.js b/modern/src/map/PositionsMap.js
index fa7b431a..4a590b7b 100644
--- a/modern/src/map/PositionsMap.js
+++ b/modern/src/map/PositionsMap.js
@@ -10,6 +10,7 @@ import StatusView from './StatusView';
 
 const PositionsMap = ({ positions }) => {
   const id = 'positions';
+  const clusters = `${id}-clusters`;
 
   const history = useHistory();
   const devices = useSelector(state => state.devices.items);
@@ -26,7 +27,7 @@ const PositionsMap = ({ positions }) => {
   const onMouseEnter = () => map.getCanvas().style.cursor = 'pointer';
   const onMouseLeave = () => map.getCanvas().style.cursor = '';
 
-  const onClickCallback = useCallback(event => {
+  const onMarkerClick = useCallback(event => {
     const feature = event.features[0];
     let coordinates = feature.geometry.coordinates.slice();
     while (Math.abs(event.lngLat.lng - coordinates[0]) > 180) {
@@ -50,18 +51,35 @@ const PositionsMap = ({ positions }) => {
       .addTo(map);
   }, [history]);
 
+  const onClusterClick = event => {
+    const features = map.queryRenderedFeatures(event.point, {
+      layers: [clusters],
+    });
+    const clusterId = features[0].properties.cluster_id;
+    map.getSource(id).getClusterExpansionZoom(clusterId, (error, zoom) => {
+      if (!error) map.easeTo({
+        center: features[0].geometry.coordinates,
+        zoom: zoom,
+      });
+    });
+  };
+
   useEffect(() => {
     map.addSource(id, {
       'type': 'geojson',
       'data': {
         type: 'FeatureCollection',
         features: [],
-      }
+      },
+      'cluster': true,
+      'clusterMaxZoom': 14,
+      'clusterRadius': 50,
     });
     map.addLayer({
       'id': id,
       'type': 'symbol',
       'source': id,
+      'filter': ['!', ['has', 'point_count']],
       'layout': {
         'icon-image': '{category}',
         'icon-allow-overlap': true,
@@ -77,22 +95,42 @@ const PositionsMap = ({ positions }) => {
         'text-halo-width': 1,
       },
     });
+    map.addLayer({
+      'id': clusters,
+      'type': 'symbol',
+      'source': id,
+      'filter': ['has', 'point_count'],
+      'layout': {
+        'icon-image': 'background',
+        'text-field': '{point_count_abbreviated}',
+        'text-font': ['Roboto Regular'],
+        'text-size': 14,
+      },
+    });
+
 
     map.on('mouseenter', id, onMouseEnter);
     map.on('mouseleave', id, onMouseLeave);
-    map.on('click', id, onClickCallback);
+    map.on('mouseenter', clusters, onMouseEnter);
+    map.on('mouseleave', clusters, onMouseLeave);
+    map.on('click', id, onMarkerClick);
+    map.on('click', clusters, onClusterClick);
 
     return () => {
       Array.from(map.getContainer().getElementsByClassName('mapboxgl-popup')).forEach(el => el.remove());
 
       map.off('mouseenter', id, onMouseEnter);
       map.off('mouseleave', id, onMouseLeave);
-      map.off('click', id, onClickCallback);
+      map.off('mouseenter', clusters, onMouseEnter);
+      map.off('mouseleave', clusters, onMouseLeave);
+      map.off('click', id, onMarkerClick);
+      map.off('click', clusters, onClusterClick);
 
       map.removeLayer(id);
+      map.removeLayer(clusters);
       map.removeSource(id);
     };
-  }, [onClickCallback]);
+  }, [onMarkerClick]);
 
   useEffect(() => {
     map.getSource(id).setData({
diff --git a/modern/src/map/mapUtil.js b/modern/src/map/mapUtil.js
index e7dc0327..4780940d 100644
--- a/modern/src/map/mapUtil.js
+++ b/modern/src/map/mapUtil.js
@@ -9,8 +9,7 @@ export const loadImage = (url) => {
   });
 };
 
-export const loadIcon = async (key, background, url) => {
-  const image = await loadImage(url);
+export const loadIcon = async (background, url) => {
   const pixelRatio = window.devicePixelRatio;
 
   const canvas = document.createElement('canvas');
@@ -22,10 +21,13 @@ export const loadIcon = async (key, background, url) => {
   const context = canvas.getContext('2d');
   context.drawImage(background, 0, 0, canvas.width, canvas.height);
 
-  const iconRatio = 0.5;
-  const imageWidth = canvas.width * iconRatio;
-  const imageHeight = canvas.height * iconRatio;
-  context.drawImage(image, (canvas.width - imageWidth) / 2, (canvas.height - imageHeight) / 2, imageWidth, imageHeight);
+  if (url) {
+    const image = await loadImage(url);
+    const iconRatio = 0.5;
+    const imageWidth = canvas.width * iconRatio;
+    const imageHeight = canvas.height * iconRatio;
+    context.drawImage(image, (canvas.width - imageWidth) / 2, (canvas.height - imageHeight) / 2, imageWidth, imageHeight);
+  }
 
   return context.getImageData(0, 0, canvas.width, canvas.height);
 };
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