calculate geo bounds (#8321)

Signed-off-by: Kerry Archibald <kerrya@element.io>

src/utils/beacon/bounds.ts

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+/*
+Copyright 2022 The Matrix.org Foundation C.I.C
+
+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 { Beacon } from "matrix-js-sdk/src/matrix";
+
+import { parseGeoUri } from "../location";
+
+export type Bounds = {
+    north: number;
+    east: number;
+    west: number;
+    south: number;
+};
+
+/**
+ * Get the geo bounds of given list of beacons
+ *
+ * Latitude:
+ * equator: 0, North pole: 90, South pole -90
+ * Longitude:
+ * Prime Meridian (Greenwich): 0
+ * east of Greenwich has a positive longitude, max 180
+ * west of Greenwich has a negative longitude, min -180
+ */
+export const getBeaconBounds = (beacons: Beacon[]): Bounds | undefined => {
+    const coords = beacons.filter(beacon => !!beacon.latestLocationState)
+        .map(beacon => parseGeoUri(beacon.latestLocationState.uri));
+
+    if (!coords.length) {
+        return;
+    }
+
+    // sort descending
+    const sortedByLat = [...coords].sort((left, right) => right.latitude - left.latitude);
+    const sortedByLong = [...coords].sort((left, right) => right.longitude - left.longitude);
+
+    return {
+        north: sortedByLat[0].latitude,
+        south: sortedByLat[sortedByLat.length - 1].latitude,
+        east: sortedByLong[0].longitude,
+        west: sortedByLong[sortedByLong.length -1].longitude,
+    };
+};

test/utils/beacon/bounds-test.ts

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+/*
+Copyright 2022 The Matrix.org Foundation C.I.C
+
+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 { Beacon } from "matrix-js-sdk/src/matrix";
+
+import { Bounds, getBeaconBounds } from "../../../src/utils/beacon/bounds";
+import { makeBeaconEvent, makeBeaconInfoEvent } from "../../test-utils";
+
+describe('getBeaconBounds()', () => {
+    const userId = '@user:server';
+    const roomId = '!room:server';
+    const makeBeaconWithLocation = (latLon: {lat: number, lon: number}) => {
+        const geoUri = `geo:${latLon.lat},${latLon.lon}`;
+        const beacon = new Beacon(makeBeaconInfoEvent(userId, roomId, { isLive: true }));
+        // @ts-ignore private prop, sets internal live property so addLocations works
+        beacon.checkLiveness();
+        const location = makeBeaconEvent(userId, {
+            beaconInfoId: beacon.beaconInfoId,
+            geoUri,
+            timestamp: Date.now() + 1,
+        });
+        beacon.addLocations([location]);
+
+        return beacon;
+    };
+
+    const geo = {
+        // northern hemi
+        // west of greenwich
+        london: { lat: 51.5, lon: -0.14 },
+        reykjavik: { lat: 64.08, lon: -21.82 },
+        // east of greenwich
+        paris: { lat: 48.85, lon: 2.29 },
+        // southern hemi
+        // east
+        auckland: { lat: -36.85, lon: 174.76 }, // nz
+        // west
+        lima: { lat: -12.013843, lon: -77.008388 }, // peru
+    };
+
+    const london = makeBeaconWithLocation(geo.london);
+    const reykjavik = makeBeaconWithLocation(geo.reykjavik);
+    const paris = makeBeaconWithLocation(geo.paris);
+    const auckland = makeBeaconWithLocation(geo.auckland);
+    const lima = makeBeaconWithLocation(geo.lima);
+
+    it('should return undefined when there are no beacons', () => {
+        expect(getBeaconBounds([])).toBeUndefined();
+    });
+
+    it('should return undefined when no beacons have locations', () => {
+        const beacon = new Beacon(makeBeaconInfoEvent(userId, roomId));
+        expect(getBeaconBounds([beacon])).toBeUndefined();
+    });
+
+    type TestCase = [string, Beacon[], Bounds];
+    it.each<TestCase>([
+        ['one beacon', [london],
+            { north: geo.london.lat, south: geo.london.lat, east: geo.london.lon, west: geo.london.lon },
+        ],
+        ['beacons in the northern hemisphere, west of meridian',
+            [london, reykjavik],
+            { north: geo.reykjavik.lat, south: geo.london.lat, east: geo.london.lon, west: geo.reykjavik.lon },
+        ],
+        ['beacons in the northern hemisphere, both sides of meridian',
+            [london, reykjavik, paris],
+            // reykjavik northmost and westmost, paris southmost and eastmost
+            { north: geo.reykjavik.lat, south: geo.paris.lat, east: geo.paris.lon, west: geo.reykjavik.lon },
+        ],
+        ['beacons in the southern hemisphere',
+            [auckland, lima],
+            // lima northmost and westmost, auckland southmost and eastmost
+            { north: geo.lima.lat, south: geo.auckland.lat, east: geo.auckland.lon, west: geo.lima.lon },
+        ],
+        ['beacons in both hemispheres',
+            [auckland, lima, paris],
+            { north: geo.paris.lat, south: geo.auckland.lat, east: geo.auckland.lon, west: geo.lima.lon },
+        ],
+    ])('gets correct bounds for %s', (_description, beacons, expectedBounds) => {
+        expect(getBeaconBounds(beacons)).toEqual(expectedBounds);
+    });
+});