feat: coveringGeohash funciton added

Adds funtion which given an envelope returns up to four geohashes which cover the envelope.

Author: LinusWallin

src/main/java/com/esri/core/geometry/Geohash.java

@@ -176,6 +176,44 @@ public static String containingGeohash(Envelope2D envelope) {
  * @return up to four geohashes that completely cover given envelope
  */
  public static String[] coveringGeohash(Envelope2D envelope) {
- return new String[] {};
+
+ String[] geoHashes = new String[4];
+
+ double xmin = envelope.xmin;
+ double ymin = envelope.ymin;
+ double xmax = envelope.xmax;
+ double ymax = envelope.ymax;
+
+ if (NumberUtils.isNaN(xmax)) {
+ return new String[] {""};
+ }
+ String[] geoHash = {containingGeohash(envelope)};
+ if (xmin == xmax && ymin == ymax) {
+ Point2D p = new Point2D(xmax, ymax);
+ return geoHash;
+ }
+ if (geoHash[0] != ""){
+ return geoHash;
+ }
+
+ int grid = 45;
+ int gridMaxLon = (int)Math.floor(xmax/grid);
+ int gridMinLon = (int)Math.floor(xmin/grid);
+ int gridMaxLat = (int)Math.floor(ymax/grid);
+ int gridMinLat = (int)Math.floor(ymin/grid);
+ int deltaLon = gridMaxLon - gridMinLon + 1;
+ int deltaLat = gridMaxLat - gridMinLat + 1;
+
+ if (deltaLon * deltaLat > 4){
+ return geoHashes;
+ } else {
+ for (int i = 0; i < deltaLon; i++){
+ for (int j = 0; j < deltaLat; j++){
+ Point2D p = new Point2D(gridMinLon + i * grid, gridMinLat + j * grid);
+ geoHashes[i*deltaLat] = toGeohash(p, 1);
+ }
+ }
+ }
+ return geoHashes;
  }
 }