Fix north pole overflow error in GeoHashUtils.bbox() (#32891)

Fixes an overflow error in  GeoHashUtils.bbox() calculation of a
bounding box for geohashes with maximum precision located next to the
north pole.

Author: imotov

server/src/main/java/org/elasticsearch/common/geo/GeoHashUtils.java

@@ -25,6 +25,8 @@
 import java.util.ArrayList;
 import java.util.Collection;
 
+import static org.apache.lucene.geo.GeoUtils.MAX_LAT_INCL;
+
 /**
  * Utilities for converting to/from the GeoHash standard
  *
@@ -48,6 +50,8 @@ public class GeoHashUtils {
     private static final double LAT_SCALE = (0x1L<<BITS)/180.0D;
     private static final double LON_SCALE = (0x1L<<BITS)/360.0D;
     private static final short MORTON_OFFSET = (BITS<<1) - (PRECISION*5);
+    /** Bit encoded representation of the latitude of north pole */
+    private static final long MAX_LAT_BITS = (0x1L << (PRECISION * 5 / 2)) - 1;
 
     // No instance:
     private GeoHashUtils() {
@@ -218,12 +222,19 @@ public static Rectangle bbox(final String geohash) {
         long ghLong = longEncode(geohash, len);
         // shift away the level
         ghLong >>>= 4;
-        // deinterleave and add 1 to lat and lon to get topRight
-        long lat = BitUtil.deinterleave(ghLong >>> 1) + 1;
-        long lon = BitUtil.deinterleave(ghLong) + 1;
-        GeoPoint topRight = GeoPoint.fromGeohash(BitUtil.interleave((int)lon, (int)lat) << 4 | len);
-
-        return new Rectangle(bottomLeft.lat(), topRight.lat(), bottomLeft.lon(), topRight.lon());
+        // deinterleave
+        long lon = BitUtil.deinterleave(ghLong >>> 1);
+        long lat = BitUtil.deinterleave(ghLong);
+        if (lat < MAX_LAT_BITS) {
+            // add 1 to lat and lon to get topRight
+            GeoPoint topRight = GeoPoint.fromGeohash(BitUtil.interleave((int)(lat + 1), (int)(lon + 1)) << 4 | len);
+            return new Rectangle(bottomLeft.lat(), topRight.lat(), bottomLeft.lon(), topRight.lon());
+        } else {
+            // We cannot go north of north pole, so just using 90 degrees instead of calculating it using
+            // add 1 to lon to get lon of topRight, we are going to use 90 for lat
+            GeoPoint topRight = GeoPoint.fromGeohash(BitUtil.interleave((int)lat, (int)(lon + 1)) << 4 | len);
+            return new Rectangle(bottomLeft.lat(), MAX_LAT_INCL, bottomLeft.lon(), topRight.lon());
+        }
     }
 
     /**

server/src/test/java/org/elasticsearch/common/geo/GeoHashTests.java

@@ -98,6 +98,11 @@ public void testLongGeohashes() {
         }
     }
 
+    public void testNorthPoleBoundingBox() {
+        Rectangle bbox = GeoHashUtils.bbox("zzbxfpgzupbx"); // Bounding box with maximum precision touching north pole
+        assertEquals(90.0, bbox.maxLat, 0.0000001); // Should be 90 degrees
+    }
+
     public void testInvalidGeohashes() {
         IllegalArgumentException ex;