EAH - Convert geohash decode code to typescript (#23955)

* Convert geohash decode code to typescript

* Change decode geohash js file over to ts file

* Update notice

NOTICE.txt

@@ -133,10 +133,6 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 
----
-This product bundles geohash.js which is available under a
-"MIT" license.  For details, see src/ui/public/utils/decode_geo_hash.js.
-
 ---
 This product includes code that is based on flot-charts, which was available
 under a "MIT" license.

src/ui/public/utils/decode_geo_hash.ts

@@ -0,0 +1,91 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you 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.
+ */
+
+interface Coordinates {
+  latitude: number[];
+  longitude: number[];
+}
+
+export function decodeGeoHash(geohash: number[]): Coordinates {
+  const BITS: number[] = [16, 8, 4, 2, 1];
+  const BASE32: string = '0123456789bcdefghjkmnpqrstuvwxyz';
+  let isEven: boolean = true;
+  const lat: number[] = [];
+  const lon: number[] = [];
+  lat[0] = -90.0;
+  lat[1] = 90.0;
+  lon[0] = -180.0;
+  lon[1] = 180.0;
+  let latErr: number = 90.0;
+  let lonErr: number = 180.0;
+  for (const geohashEl of geohash) {
+    const c: string = geohashEl.toString();
+    const cd: number = BASE32.indexOf(c);
+    for (let j = 0; j < 5; j++) {
+      const mask: number = BITS[j];
+      if (isEven) {
+        lonErr = lonErr /= 2;
+        refine_interval(lon, cd, mask);
+      } else {
+        latErr = latErr /= 2;
+        refine_interval(lat, cd, mask);
+      }
+      isEven = !isEven;
+    }
+  }
+  lat[2] = (lat[0] + lat[1]) / 2;
+  lon[2] = (lon[0] + lon[1]) / 2;
+  return {
+    latitude: lat,
+    longitude: lon,
+  } as Coordinates;
+}
+
+function refine_interval(interval: number[], cd: number, mask: number) {
+  if (cd & mask) { /* tslint:disable-line */
+    interval[0] = (interval[0] + interval[1]) / 2;
+  } else {
+    interval[1] = (interval[0] + interval[1]) / 2;
+  }
+}
+
+/**
+ * Get the number of geohash cells for a given precision
+ *
+ * @param {number} precision the geohash precision (1<=precision<=12).
+ * @param {number} axis constant for the axis 0=lengthwise (ie. columns, along longitude), 1=heightwise (ie. rows, along latitude).
+ * @returns {number} Number of geohash cells (rows or columns) at that precision
+ */
+function geohashCells(precision: number, axis: number) {
+  let cells = 1;
+  for (let i = 1; i <= precision; i += 1) {
+    /*On odd precisions, rows divide by 4 and columns by 8. Vice-versa on even precisions */
+    cells *= i % 2 === axis ? 4 : 8;
+  }
+  return cells;
+}
+
+/**
+ * Get the number of geohash columns (world-wide) for a given precision
+ * @param precision the geohash precision
+ * @returns {number} the number of columns
+ */
+export function geohashColumns(precision: number): number {
+  return geohashCells(precision, 0);
+}