implemented naturalsorter for engine

Signed-off-by: Chanwit Kaewkasi <chanwit@gmail.com>

cluster/engine_sorter.go

@@ -1,5 +1,9 @@
 package cluster
 
+import (
+	"github.com/skarademir/naturalsort"
+)
+
 // EngineSorter implements the Sort interface to sort Cluster.Engine.
 // It is not guaranteed to be a stable sort.
 type EngineSorter []*Engine
@@ -17,5 +21,5 @@ func (s EngineSorter) Swap(i, j int) {
 // Less reports whether the engine with index i should sort before the engine with index j.
 // Engines are sorted chronologically by name.
 func (s EngineSorter) Less(i, j int) bool {
-	return s[i].Name < s[j].Name
+	return naturalsort.NaturalSort([]string{s[i].Name, s[j].Name}).Less(0, 1)
 }

cluster/engine_sorter_test.go

@@ -16,3 +16,17 @@ func TestEngineSorter(t *testing.T) {
 	assert.Equal(t, engines[1].Name, "name2")
 	assert.Equal(t, engines[2].Name, "name3")
 }
+
+func TestNaturalSort(t *testing.T) {
+	engines := []*Engine{{Name: "machine10"},
+		{Name: "machine9"},
+		{Name: "machine1"},
+		{Name: "machine11"}}
+
+	sort.Sort(EngineSorter(engines))
+
+	assert.Equal(t, engines[0].Name, "machine1")
+	assert.Equal(t, engines[1].Name, "machine9")
+	assert.Equal(t, engines[2].Name, "machine10")
+	assert.Equal(t, engines[3].Name, "machine11")
+}