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supercluster.ts
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supercluster.ts
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/**
* Copyright 2021 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import { AbstractAlgorithm, AlgorithmInput, AlgorithmOutput } from "./core";
import SuperCluster, { ClusterFeature } from "supercluster";
import { Cluster } from "../cluster";
import equal from "fast-deep-equal";
export type SuperClusterOptions = SuperCluster.Options<
{ [name: string]: any },
{ [name: string]: any }
>;
/**
* A very fast JavaScript algorithm for geospatial point clustering using KD trees.
*
* @see https://www.npmjs.com/package/supercluster for more information on options.
*/
export class SuperClusterAlgorithm extends AbstractAlgorithm {
protected superCluster: SuperCluster;
protected markers: google.maps.Marker[];
protected clusters: Cluster[];
protected state: { zoom: number };
constructor({ maxZoom, radius = 60, ...options }: SuperClusterOptions) {
super({ maxZoom });
this.superCluster = new SuperCluster({
maxZoom: this.maxZoom,
radius,
...options,
});
this.state = { zoom: null };
}
public calculate(input: AlgorithmInput): AlgorithmOutput {
let changed = false;
if (!equal(input.markers, this.markers)) {
changed = true;
// TODO use proxy to avoid copy?
this.markers = [...input.markers];
const points = this.markers.map((marker) => {
return {
type: "Feature" as const,
geometry: {
type: "Point" as const,
coordinates: [
marker.getPosition().lng(),
marker.getPosition().lat(),
],
},
properties: { marker },
};
});
this.superCluster.load(points);
}
const state = { zoom: input.map.getZoom() };
if (!changed) {
if (this.state.zoom > this.maxZoom && state.zoom > this.maxZoom) {
// still beyond maxZoom, no change
} else {
changed = changed || !equal(this.state, state);
}
}
this.state = state;
if (changed) {
this.clusters = this.cluster(input);
}
return { clusters: this.clusters, changed };
}
public cluster({ map }: AlgorithmInput): Cluster[] {
return this.superCluster
.getClusters([-180, -90, 180, 90], Math.round(map.getZoom()))
.map(this.transformCluster.bind(this));
}
protected transformCluster({
geometry: {
coordinates: [lng, lat],
},
properties,
}: ClusterFeature<{ marker: google.maps.Marker }>): Cluster {
if (properties.cluster) {
return new Cluster({
markers: this.superCluster
.getLeaves(properties.cluster_id, Infinity)
.map((leaf) => leaf.properties.marker),
position: new google.maps.LatLng({ lat, lng }),
});
} else {
const marker = properties.marker;
return new Cluster({
markers: [marker],
position: marker.getPosition(),
});
}
}
}