// [START fs_geo_add_hash]

// Compute the GeoHash for a lat/lng point

const lat = 51.5074;

const lng = 0.1278;

const hash = geofire.geohashForLocation([lat, lng]);

// Add the hash and the lat/lng to the document. We will use the hash

// for queries and the lat/lng for distance comparisons.

const londonRef = db.collection('cities').doc('LON');

londonRef.update({

geohash: hash,

lat: lat,

lng: lng

}).then(() => {

// [START_EXCLUDE]

done();

// [END_EXCLUDE]

});

// [END fs_geo_add_hash]

// [START fs_geo_query_hashes]

// Find cities within 50km of London

const center = [51.5074, 0.1278];

const radiusInM = 50 * 1000;

// Each item in 'bounds' represents a startAt/endAt pair. We have to issue

// a separate query for each pair. There can be up to 9 pairs of bounds

// depending on overlap, but in most cases there are 4.

const bounds = geofire.geohashQueryBounds(center, radiusInM);

const promises = [];

for (const b of bounds) {

const q = db.collection('cities')

.orderBy('geohash')

.startAt(b[0])

.endAt(b[1]);

promises.push(q.get());

}

// Collect all the query results together into a single list

Promise.all(promises).then((snapshots) => {

const matchingDocs = [];

for (const snap of snapshots) {

for (const doc of snap.docs) {

const lat = doc.get('lat');

const lng = doc.get('lng');

// We have to filter out a few false positives due to GeoHash

// accuracy, but most will match

const distanceInKm = geofire.distanceBetween([lat, lng], center);

const distanceInM = distanceInKm * 1000;

if (distanceInM <= radiusInM) {

matchingDocs.push(doc);

}

}

}

return matchingDocs;

}).then((matchingDocs) => {

// Process the matching documents

// [START_EXCLUDE]

done(matchingDocs);

// [END_EXCLUDE]

});

// [END fs_geo_query_hashes]