feat: added full support for vertex mode

README.md

@@ -123,10 +123,10 @@ func ExampleLatLngToCell() {
 | `directedEdgeToCells`        | `DirectedEdge#Cells`                               |
 | `originToDirectedEdges`      | `Cell#DirectedEdges`                               |
 | `directedEdgeToBoundary`     | `DirectedEdge#Boundary`                            |
-| `cellToVertex`               | TODO                                               |
-| `cellToVertexes`             | TODO                                               |
-| `vertexToLatLng`             | TODO                                               |
-| `isValidVertex`              | TODO                                               |
+| `cellToVertex`               | `CellToVertex`                                     |
+| `cellToVertexes`             | `cellToVertexes`                                   |
+| `vertexToLatLng`             | `VertexToLatLng`                                   |
+| `isValidVertex`              | `IsValidVertex`                                    |
 | `gridDistance`               | `GridDistance`, `Cell#GridDistance`                |
 | `gridPathCells`              | `GridPath`, `Cell#GridPath`                        |
 | `cellToLocalIj`              | `CellToLocalIJ`                                    |

h3.go

@@ -60,8 +60,9 @@ const (
 	base16  = 16
 	bitSize = 64
 
-	numCellEdges = 6
-	numEdgeCells = 2
+	numCellEdges    = 6
+	numEdgeCells    = 2
+	numCellVertexes = 6
 
 	DegsToRads = math.Pi / 180.0
 	RadsToDegs = 180.0 / math.Pi
@@ -713,6 +714,31 @@ func LocalIJToCell(origin Cell, ij CoordIJ) Cell {
 	return Cell(out)
 }
 
+func CellToVertex(c Cell, vertexNum int) Cell {
+	var out C.H3Index
+	C.cellToVertex(C.H3Index(c), C.int(vertexNum), &out)
+
+	return Cell(out)
+}
+
+func CellToVertexes(c Cell) []Cell {
+	out := make([]C.H3Index, numCellVertexes)
+	C.cellToVertexes(C.H3Index(c), &out[0])
+
+	return cellsFromC(out, true, false)
+}
+
+func VertexToLatLng(vertex Cell) LatLng {
+	var out C.LatLng
+	C.vertexToLatLng(C.H3Index(vertex), &out)
+
+	return latLngFromC(out)
+}
+
+func IsValidVertex(c Cell) bool {
+	return C.isValidVertex(C.H3Index(c)) == 1
+}
+
 func maxGridDiskSize(k int) int {
 	return 3*k*(k+1) + 1
 }

h3_test.go

@@ -609,6 +609,7 @@ func TestPentagons(t *testing.T) {
 	t.Parallel()
 
 	for _, res := range []int{0, 8, 15} {
+		res := res
 		t.Run(fmt.Sprintf("res=%d", res), func(t *testing.T) {
 			t.Parallel()
 			pentagons := Pentagons(res)
@@ -621,6 +622,83 @@ func TestPentagons(t *testing.T) {
 	}
 }
 
+func TestCellToVertex(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		cell           Cell
+		expectedVertex Cell
+		vertexNum      int
+	}{
+		{cell: validCell, expectedVertex: 0x2050dab63fffffff, vertexNum: 0},
+		{cell: validCell, expectedVertex: 0, vertexNum: 6}, // vertex num should be between 0 and 5 for hexagonal cells.
+	}
+
+	for i, tc := range testCases {
+		tc := tc
+
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			t.Parallel()
+
+			vertex := CellToVertex(tc.cell, tc.vertexNum)
+			assertEqual(t, tc.expectedVertex, vertex)
+		})
+	}
+}
+
+func TestCellToVertexes(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		cell        Cell
+		numVertexes int
+	}{
+		{cell: validCell, numVertexes: 6},
+		{cell: pentagonCell, numVertexes: 5},
+		{cell: -1, numVertexes: 0}, // Invalid cel.
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(fmt.Sprint(tc.numVertexes), func(t *testing.T) {
+			t.Parallel()
+
+			vertexes := CellToVertexes(tc.cell)
+			assertEqual(t, tc.numVertexes, len(vertexes))
+		})
+	}
+}
+
+func TestVertexToLatLng(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		vertex         Cell
+		expectedLatLng LatLng
+	}{
+		{vertex: CellToVertex(validCell, 0), expectedLatLng: LatLng{Lat: 67.22475, Lng: -168.52301}},
+		{vertex: -1, expectedLatLng: LatLng{}}, // Invalid vertex.
+	}
+
+	for i, tc := range testCases {
+		tc := tc
+
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			t.Parallel()
+
+			latLng := VertexToLatLng(tc.vertex)
+			assertEqualLatLng(t, tc.expectedLatLng, latLng)
+		})
+	}
+}
+
+func TestIsValidVertex(t *testing.T) {
+	t.Parallel()
+
+	assertFalse(t, IsValidVertex(0))
+	assertTrue(t, IsValidVertex(2473183460575936511))
+}
+
 func equalEps(expected, actual float64) bool {
 	return math.Abs(expected-actual) < eps
 }