Add common strategies

Signed-off-by: Bryce Palmer <bpalmer@redhat.com>

prune/strategies.go

@@ -0,0 +1,62 @@
+// Copyright 2021 The Operator-SDK Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package prune
+
+import (
+	"context"
+	"sort"
+	"time"
+
+	"sigs.k8s.io/controller-runtime/pkg/client"
+)
+
+// NewPruneByCountStrategy returns a StrategyFunc that will return a list of
+// resources to prune based on a maximum count of resources allowed.
+// If the max count of resources is exceeded, the oldest resources are prioritized for pruning
+func NewPruneByCountStrategy(count int) StrategyFunc {
+	return func(ctx context.Context, objs []client.Object) ([]client.Object, error) {
+
+		if len(objs) <= count {
+			return nil, nil
+		}
+
+		// sort objects by creation date
+		sortedObjs := objs
+
+		sort.SliceStable(sortedObjs, func(i, j int) bool {
+			iTimestamp := sortedObjs[i].GetCreationTimestamp()
+			jTimestamp := sortedObjs[j].GetCreationTimestamp()
+			return iTimestamp.Before(&jTimestamp)
+		})
+
+		return sortedObjs[count:], nil
+	}
+}
+
+// NewPruneByDateStrategy returns a StrategyFunc that will return a list of
+// resources to prune where the resource CreationTimestamp is after the given time.Time.
+func NewPruneByDateStrategy(date time.Time) StrategyFunc {
+	return func(ctx context.Context, objs []client.Object) ([]client.Object, error) {
+		var objsToPrune []client.Object
+
+		for _, obj := range objs {
+			if obj.GetCreationTimestamp().After(date) {
+				objsToPrune = append(objsToPrune, obj)
+			}
+		}
+
+		return objsToPrune, nil
+	}
+}