controller: function to sort objects by timestamp

controller/object.go

@@ -1,9 +1,12 @@
 package controller
 
 import (
+	"fmt"
+
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/utils/ptr"
 
 	"github.com/kuadrant/policy-machinery/machinery"
 )
@@ -13,11 +16,15 @@ type Object interface {
 	metav1.Object
 }
 
-// RuntimeObject is a cluster runtime object that implements machinery.Object interface
+// RuntimeObject is a wrapper around a Kubernetes runtime object, that also implements the machinery.Object interface
+// Use it for wrapping runtime objects that do not natively implement machinery.Object, so such object can be added to
+// a machinery.Topology
 type RuntimeObject struct {
 	Object
 }
 
+var _ machinery.Object = &RuntimeObject{}
+
 func (o *RuntimeObject) GroupVersionKind() schema.GroupVersionKind {
 	return o.Object.GetObjectKind().GroupVersionKind()
 }
@@ -41,3 +48,20 @@ func ObjectAs[T any](obj Object, _ int) T {
 	o, _ := obj.(T)
 	return o
 }
+
+// ObjectsByCreationTimestamp is a slice of RuntimeObject that can be sorted by creation timestamp
+// RuntimeObjects with the oldest creation timestamp will appear first; if two objects have the same creation timestamp,
+// the object appearing first in alphabetical order by namespace/name will appear first.
+type ObjectsByCreationTimestamp []Object
+
+func (a ObjectsByCreationTimestamp) Len() int      { return len(a) }
+func (a ObjectsByCreationTimestamp) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
+func (a ObjectsByCreationTimestamp) Less(i, j int) bool {
+	p1Time := ptr.To(a[i].GetCreationTimestamp())
+	p2Time := ptr.To(a[j].GetCreationTimestamp())
+	if !p1Time.Equal(p2Time) {
+		return p1Time.Before(p2Time)
+	}
+	//  The object appearing first in alphabetical order by "{namespace}/{name}".
+	return fmt.Sprintf("%s/%s", a[i].GetNamespace(), a[i].GetName()) < fmt.Sprintf("%s/%s", a[j].GetNamespace(), a[j].GetName())
+}

controller/object_test.go

@@ -0,0 +1,37 @@
+package controller
+
+import (
+	"sort"
+	"testing"
+	"time"
+
+	"github.com/samber/lo"
+	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+func TestObjectsByCreationTimestamp(t *testing.T) {
+	pods := []*corev1.Pod{
+		{ObjectMeta: metav1.ObjectMeta{Name: "pod1", CreationTimestamp: metav1.Time{Time: time.Unix(1, 0)}}},
+		{ObjectMeta: metav1.ObjectMeta{Name: "pod2", CreationTimestamp: metav1.Time{Time: time.Unix(2, 0)}}},
+		{ObjectMeta: metav1.ObjectMeta{Name: "pod3", CreationTimestamp: metav1.Time{Time: time.Unix(1, 0)}}},
+	}
+	objs := lo.Map(pods, func(pod *corev1.Pod, _ int) Object { return pod })
+	sort.Sort(ObjectsByCreationTimestamp(objs))
+	if objs[0].GetName() != "pod1" {
+		t.Errorf("expected pod1, got %s", objs[0].GetName())
+	}
+	if objs[1].GetName() != "pod3" {
+		t.Errorf("expected pod3, got %s", objs[1].GetName())
+	}
+	if objs[2].GetName() != "pod2" {
+		t.Errorf("expected pod2, got %s", objs[2].GetName())
+	}
+}
+
+func TestObjectAs(t *testing.T) {
+	var obj Object = &corev1.Pod{}
+	if ObjectAs[*corev1.Pod](obj, 0) == nil {
+		t.Errorf("expected *corev1.Pod, got nil")
+	}
+}