From 22412b0cfc9bd23dc605346603efb844dfad9fa9 Mon Sep 17 00:00:00 2001
From: Robert Brown <robert@slan124.info>
Date: Wed, 1 Dec 2021 16:04:19 +0000
Subject: [PATCH] SetToLinkedGeo bug and update to latest C library (#49)

* Correctly set next for multipolygon SetToLinkedGeo

* Update h3 C library to v3.7.2
---
 v3/H3_VERSION |  2 +-
 v3/h3.go      |  5 +++++
 v3/h3_algos.c |  5 ++++-
 v3/h3_test.go | 43 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/v3/H3_VERSION b/v3/H3_VERSION
index 1885263..2272683 100644
--- a/v3/H3_VERSION
+++ b/v3/H3_VERSION
@@ -1 +1 @@
-v3.7.1
+v3.7.2
diff --git a/v3/h3.go b/v3/h3.go
index 00753e3..1b8a93a 100644
--- a/v3/h3.go
+++ b/v3/h3.go
@@ -609,6 +609,11 @@ func linkedGeoPolygonFromC(cg *C.LinkedGeoPolygon) LinkedGeoPolygon {
 	g.First = linkedGeoLoopFromC(cg.first)
 	g.Last = linkedGeoLoopFromC(cg.last)
 
+	if cg.next != nil {
+		next := linkedGeoPolygonFromC(cg.next)
+		g.Next = &next
+	}
+
 	return g
 }
 
diff --git a/v3/h3_algos.c b/v3/h3_algos.c
index 769a1c8..ac0a596 100644
--- a/v3/h3_algos.c
+++ b/v3/h3_algos.c
@@ -317,7 +317,10 @@ H3Index h3NeighborRotations(H3Index origin, Direction dir, int* rotations) {
         } else {
             Direction oldDigit = H3_GET_INDEX_DIGIT(out, r + 1);
             Direction nextDir;
-            if (isResClassIII(r + 1)) {
+            if (oldDigit == INVALID_DIGIT) {
+                // Only possible on invalid input
+                return H3_NULL;
+            } else if (isResClassIII(r + 1)) {
                 H3_SET_INDEX_DIGIT(out, r + 1, NEW_DIGIT_II[oldDigit][dir]);
                 nextDir = NEW_ADJUSTMENT_II[oldDigit][dir];
             } else {
diff --git a/v3/h3_test.go b/v3/h3_test.go
index 25a9bfb..721163b 100644
--- a/v3/h3_test.go
+++ b/v3/h3_test.go
@@ -147,6 +147,32 @@ var (
 			0x872f5a374ffffff,
 			0x872f5a329ffffff,
 		},
+		{
+			0x89194ad36a3ffff,
+			0x89194ad3263ffff,
+			0x89194ad326fffff,
+			0x89194ad149bffff,
+			0x89194ad1493ffff,
+			0x89194ad322bffff,
+			0x89194ad3277ffff,
+			0x89194ad338bffff,
+			0x89194ad3313ffff,
+			0x89194ad3317ffff,
+			0x89194ad33bbffff,
+			0x89194ad3387ffff,
+			0x89194ad3383ffff,
+			0x89194ad3397ffff,
+			0x89194ad33b3ffff,
+			0x89194ad314fffff,
+			0x89194ad3143ffff,
+			0x89194ad315bffff,
+			0x88194ad369fffff,
+			0x88194ad361fffff,
+			0x88194ad363fffff,
+			0x88194ad30dfffff,
+			0x88194ad347fffff,
+			0x88194ad345fffff,
+		},
 	}
 
 	validGeoCoordB = GeoCoord{
@@ -501,6 +527,23 @@ func TestSetToLinkedGeo(t *testing.T) {
 		assert.Equal(t, float64(35.68805899195678), polygon.Last.First.Vertex.Latitude)
 		assert.Equal(t, float64(139.7268573711303), polygon.Last.First.Vertex.Longitude)
 	})
+	t.Run("Multipolygon", func(t *testing.T) {
+		t.Parallel()
+		polygon := SetToLinkedGeo(validLinkedIndexes[2])
+
+		assert.NotNil(t, polygon.First)
+		assert.NotNil(t, polygon.Last)
+		assert.NotNil(t, polygon.Next)
+
+		assert.Equal(t, float64(51.49710134101195), polygon.First.First.Vertex.Latitude)
+		assert.Equal(t, float64(-0.09036943363144687), polygon.First.First.Vertex.Longitude)
+
+		assert.Equal(t, float64(51.49794867871118), polygon.Last.First.Vertex.Latitude)
+		assert.Equal(t, float64(-0.07191264615040037), polygon.Last.First.Vertex.Longitude)
+
+		assert.Equal(t, float64(51.53058149905774), polygon.Next.First.First.Vertex.Latitude)
+		assert.Equal(t, float64(-0.07297959470277668), polygon.Next.First.First.Vertex.Longitude)
+	})
 }
 
 func TestLine(t *testing.T) {