Validate clustermap parent-child dependancy

Add ValidateClusterMap() method to confirm there are no parent-child
dependancy issues for any clustermaps.

Closes: #481
Change-Id: Ifb57b026933909a4350d71353adca23a42440a48

pkg/cluster/clustermap/errors.go

@@ -39,3 +39,13 @@ type ErrClusterNotInMap struct {
 func (e ErrClusterNotInMap) Error() string {
 	return fmt.Sprintf("cluster '%s' is not defined in cluster map %v", e.Child, e.Map)
 }
+
+// ErrClusterCircularDependency returned for circular dependencies
+type ErrClusterCircularDependency struct {
+	Parent string
+	Map    *v1alpha1.ClusterMap
+}
+
+func (e ErrClusterCircularDependency) Error() string {
+	return fmt.Sprintf("%v contains cluster referenced as both parent and child: %s", e.Map, e.Parent)
+}

pkg/cluster/clustermap/map.go

@@ -36,6 +36,7 @@ type WriteOptions struct {
 // TODO use typed cluster names
 type ClusterMap interface {
 	ParentCluster(string) (string, error)
+	ValidateClusterMap() error
 	AllClusters() []string
 	ClusterKubeconfigContext(string) (string, error)
 	Sources(string) ([]v1alpha1.KubeconfigSource, error)
@@ -66,6 +67,33 @@ func (cm clusterMap) ParentCluster(child string) (string, error) {
 	return currentCluster.Parent, nil
 }
 
+// Validates a clustermap has valid parent-child map structure
+func (cm clusterMap) ValidateClusterMap() error {
+	clusterMap := cm.AllClusters()
+	for _, childCluster := range clusterMap {
+		var parentClusters []string
+		var currentChild string = childCluster
+		for {
+			currentCluster, _ := cm.apiMap.Map[currentChild]
+			for _, c := range parentClusters {
+				if c == currentCluster.Parent {
+					// Quit on parent whos also child
+					return ErrClusterCircularDependency{Parent: childCluster, Map: cm.apiMap}
+				}
+			}
+			// Quit loop once top level of current cluster is reached
+			if currentCluster.Parent == "" {
+				break
+			}
+			parentClusters = append(parentClusters, currentCluster.Parent)
+			currentChild = currentCluster.Parent
+		}
+	}
+
+	// Return success if there are no conflicts
+	return nil
+}
+
 // AllClusters returns all clusters in a map
 func (cm clusterMap) AllClusters() []string {
 	clusters := []string{}

pkg/cluster/clustermap/map_test.go

@@ -97,6 +97,27 @@ func TestClusterMap(t *testing.T) {
 		assert.Equal(t, "", parent)
 	})
 
+	t.Run("Validate Circular Clustermap", func(t *testing.T) {
+		// Create new map with circular dependency
+		circularAPIMap := &v1alpha1.ClusterMap{
+			Map: map[string]*v1alpha1.Cluster{},
+		}
+		for key, value := range apiMap.Map {
+			newValue := *value
+			circularAPIMap.Map[key] = &newValue
+		}
+		circularAPIMap.Map["ephemeral"].Parent = "workload"
+		cMapCircular := clustermap.NewClusterMap(circularAPIMap)
+		err := cMapCircular.ValidateClusterMap()
+		assert.Error(t, err)
+	})
+
+	t.Run("Validate all Clustermaps", func(t *testing.T) {
+		// Check child clusterID against map of parent clusterID map
+		err := cMap.ValidateClusterMap()
+		assert.NoError(t, err)
+	})
+
 	t.Run("all clusters", func(t *testing.T) {
 		clusters := cMap.AllClusters()
 		assert.Len(t, clusters, 4)