UPSTREAM: <carry>: SQUASH: with shard prefix support – simplify

staging/src/k8s.io/apiserver/pkg/storage/etcd3/store_patch.go

@@ -17,66 +17,49 @@ limitations under the License.
 package etcd3
 
 import (
-	"regexp"
 	"strings"
 
 	"github.com/kcp-dev/logicalcluster/v2"
+
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
-	genericapirequest "k8s.io/apiserver/pkg/endpoints/request"
 	"k8s.io/klog/v2"
-)
 
-var (
-	// matches cluster/remainder, capturing cluster.
-	//
-	// Example: root:org:ws/some-namespace/some-name
-	// Example: root:org:ws/some-name
-	wildcardClusterNameRegex = regexp.MustCompile(`^([^/]+)\/.+`)
-
-	// matches shard/cluster/remainder, capturing shard and cluster.
-	//
-	// Example: amber/root:org:ws/some-namespace/some-name
-	// Example: amber/root:org:ws/some-name
-	wildcardShardClusterNameRegex = regexp.MustCompile(`^([^\/]+)\/([^\/]+)\/.+`)
-
-	// matches identity-or-customresources/cluster/remainder, capturing cluster
-	//
-	// Example: customresources/root:org:ws/some-namespace/some-name
-	// Example: customresources/root:org:ws/some-name
-	// Example: 2699f4d273d342adccdc8a32663408226ecf66de7d191113ed3d4dc9bccec2f2/root:org:ws/some-namespace/some-name
-	// Example: 2699f4d273d342adccdc8a32663408226ecf66de7d191113ed3d4dc9bccec2f2/root:org:ws/some-name
-	crdWildcardPartialMetadataClusterNameRegex = regexp.MustCompile(`^[^/]+\/([^/]+)\/.+`)
+	genericapirequest "k8s.io/apiserver/pkg/endpoints/request"
 )
 
-// adjustClusterNameIfWildcard determines the logical cluster name. If this is not a wildcard list/watch request,
-// the cluster name is returned unmodified. Otherwise, the cluster name is extracted from the key based on whether
-// it is a CR partial metadata request (prefix/identity/clusterName/remainder) or not (prefix/clusterName/remainder).
+// adjustClusterNameIfWildcard determines the logical cluster name. If this is not a cluster-wildcard list/watch request,
+// the cluster name is returned unmodified. Otherwise, the cluster name is extracted from the key based on whether it is
+// - a shard-wildcard request: <prefix>/shardName/clusterName/<remainder>
+// - CR partial metadata request: <prefix>/identity/clusterName/<remainder>
+// - any other request: <prefix>/clusterName/<remainder>.
 func adjustClusterNameIfWildcard(shard genericapirequest.Shard, cluster *genericapirequest.Cluster, crdRequest bool, keyPrefix, key string) logicalcluster.Name {
-	if cluster.Name != logicalcluster.Wildcard {
+	if cluster.Name != logicalcluster.Wildcard && !cluster.Wildcard { // TODO: fix this duplicity, as well
 		return cluster.Name
 	}
 
 	keyWithoutPrefix := strings.TrimPrefix(key, keyPrefix)
+	parts := strings.SplitN(keyWithoutPrefix, "/", 3)
 
-	if !shard.Wildcard() {
-		var regex *regexp.Regexp
-		if cluster.PartialMetadataRequest && crdRequest {
-			regex = crdWildcardPartialMetadataClusterNameRegex
-		} else {
-			regex = wildcardClusterNameRegex
-		}
-		matches := regex.FindStringSubmatch(keyWithoutPrefix)
-		if len(matches) >= 2 {
-			return logicalcluster.New(matches[1])
+	extract := func(minLen, i int) logicalcluster.Name {
+		if len(parts) < minLen {
+			klog.Warningf("shard=%s cluster=%s invalid key=%s had %d parts, not %d", shard, cluster, keyWithoutPrefix, len(parts), minLen)
+			return logicalcluster.Name{}
 		}
-		return logicalcluster.Name{}
+		return logicalcluster.New(parts[i])
 	}
 
-	matches := wildcardShardClusterNameRegex.FindStringSubmatch(keyWithoutPrefix)
-	if len(matches) >= 3 {
-		return logicalcluster.New(matches[2])
+	switch {
+	case shard.Wildcard():
+		// expecting shardName/clusterName/<remainder>
+		return extract(3, 1)
+	case cluster.PartialMetadataRequest && crdRequest:
+		// expecting 2699f4d273d342adccdc8a32663408226ecf66de7d191113ed3d4dc9bccec2f2/root:org:ws/<remainder>
+		// OR customresources/root:org:ws/<remainder>
+		return extract(3, 1)
+	default:
+		// expecting root:org:ws/<remainder>
+		return extract(2, 0)
 	}
-	return logicalcluster.Name{}
 }
 
 // setClusterNameOnDecodedObject applies clusterName to obj. This is necessary because we don't store the cluster