Squashed commit of the following:

commit 279212f
Author: Linus Wallin <linuswallin@live.se>
Date:   Mon Mar 4 09:46:08 2024 +0100

    fix: solves bug where precision is allowed to be too high

    Limits the precision in containingGeohash function to 6 from 24
    since the toGeohash function has been updated to only work for
    highest precision 6.

commit 2aa650f
Merge: 263f8e2 dcdb58d
Author: Linus Wallin <linuswallin@live.se>
Date:   Mon Mar 4 09:45:04 2024 +0100

    Merge branch '213-geometry-to-geohash' of github.com:DD2480-Group-3/geometry-api-java into 54-coveringGeohash

commit 263f8e2
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 19:47:34 2024 +0100

    refactor: removed missed empty line

commit 72b84f4
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 19:47:05 2024 +0100

    refactor: removed empty line

commit 6fef312
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 19:45:34 2024 +0100

    refactor: removed empty lines

commit 1287b2c
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 19:39:49 2024 +0100

    test: changed envelope to encompass 4 different parts of the geo grid

    The envelope was previously assigned wrong max x and y values, which
    resulted in errors as the coveringGeohash function didn't return
    the expected amount of geo hashes.

commit 69ca9c0
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 19:30:38 2024 +0100

    fix: solves bug which resulted in wrong geohashes

commit 2a8d131
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 19:24:32 2024 +0100

    test: updated tests to match the changes of the function in last commit

commit bb45871
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 19:24:02 2024 +0100

    refactor: made the return string array dynamic

commit 708542e
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 18:42:15 2024 +0100

    refactor: removes indentation error caused by merge

commit a216691
Merge: 4420765 62f7d5f
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 18:41:36 2024 +0100

    Merge branch '213-geometry-to-geohash' of github.com:DD2480-Group-3/geometry-api-java into 54-coveringGeohash

commit 4420765
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 18:37:30 2024 +0100

    test: added test cases for coveringGeohash function

commit 2c31979
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 18:15:40 2024 +0100

    refactor: removes unnecessary if statement

    Removes if statement which didn't change the outcome of the program.

commit e0b04d3
Author: Linus Wallin <linuswallin@live.se>
Date:   Sun Mar 3 17:39:37 2024 +0100

    feat: coveringGeohash funciton added

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

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

@@ -187,7 +187,7 @@ public static String containingGeohash(Envelope2D envelope) {
     double deltaLon = 360;
     double deltaLat = 180;
 
-    while (xmin == xmax && ymin == ymax && chars < 25) {
+    while (xmin == xmax && ymin == ymax && chars < 7) {
       if (chars % 2 == 0) {
         deltaLon = deltaLon / 8;
         deltaLat = deltaLat / 4;
@@ -215,6 +215,38 @@ 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[] {};
+    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 (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;
+    String[] geoHashes = new String[deltaLon * deltaLat];
+
+    if (deltaLon * deltaLat > 4){
+      return new String[] {""};
+    } else {
+      for (int i = 0; i < deltaLon; i++){
+        for (int j = 0; j < deltaLat; j++){
+          Point2D p = new Point2D(xmin + i * grid, ymin + j * grid);
+          geoHashes[i*deltaLat + j] = toGeohash(p, 1);
+        }
+      }
+    }
+    return geoHashes;
   }
 }

src/test/java/com/esri/core/geometry/TestGeohash.java

@@ -129,7 +129,54 @@ public void testContainingGeohash() {
 
   @Test
   public void testContainingGeohash2() {
-    Envelope2D envelope = new Envelope2D(18.078, 59.3564, 18.1, 59.3344);
-    assertEquals("u6sce", Geohash.containingGeohash(envelope));
+      Envelope2D envelope = new Envelope2D(18.078, 59.3564, 18.1, 59.3344);
+      assertEquals("u6sce", Geohash.containingGeohash(envelope));
   }
-}
+
+  @Test
+  public void testCoveringGeohashEmptyEnvelope() {
+    Envelope2D emptyEnv = new Envelope2D();
+    String [] coverage = Geohash.coveringGeohash(emptyEnv);
+  }
+
+  @Test
+  public void testCoveringGeohashOneGeohash() {
+    Envelope2D env = new Envelope2D(-180, -90, -149, -49);
+    String [] coverage = Geohash.coveringGeohash(env);
+    assertEquals("0", coverage[0]);
+  }
+
+  @Test
+  public void testCoveringGeohashPoint() {
+    Envelope2D env = new Envelope2D(180,90,180,90);
+    String [] coverage = Geohash.coveringGeohash(env);
+    assertEquals("zzzzzz", coverage[0]);
+  }
+
+  @Test
+  public void testCoveringGeohashTwoGeohashes() {
+    Envelope2D env = new Envelope2D(-180, -90, -180, -35);
+    String [] coverage = Geohash.coveringGeohash(env);
+    assertEquals("0", coverage[0]);
+    assertEquals("2", coverage[1]);
+  }
+
+  @Test
+  public void testCoveringGeohashThreeGeohashes() {
+    Envelope2D env = new Envelope2D(-180, -90, -180, 5);
+    String [] coverage = Geohash.coveringGeohash(env);
+    assertEquals("0", coverage[0]);
+    assertEquals("2", coverage[1]);
+    assertEquals("8", coverage[2]);
+  }
+
+  @Test
+  public void testCoveringGeohashFourGeohashes() {
+    Envelope2D env = new Envelope2D(-180, -90, -130, -40);
+    String [] coverage = Geohash.coveringGeohash(env);
+    assertEquals("0", coverage[0]);
+    assertEquals("2", coverage[1]);
+    assertEquals("1", coverage[2]);
+    assertEquals("3", coverage[3]);
+  }
+}