Add relations package to serve as a central place of finding relations between resources

Author: gauravkghildiyal

gwctl/pkg/relations/relations.go

@@ -0,0 +1,110 @@
+/*
+Copyright 2024 The Kubernetes 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 relations provides functions for navigating relationships between
+// Gateway API resources.
+package relations
+
+import (
+	gatewayv1 "sigs.k8s.io/gateway-api/apis/v1"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	types "k8s.io/apimachinery/pkg/types"
+)
+
+// ObjRef defines a reference to a Kubernetes resource, using plain strings for
+// easier comparison.
+type ObjRef struct {
+	Group     string `json:",omitempty"`
+	Kind      string `json:",omitempty"`
+	Name      string `json:",omitempty"`
+	Namespace string `json:",omitempty"`
+}
+
+// FindGatewayRefsForHTTPRoute returns Gateways which the HTTPRoute is attached
+// to.
+func FindGatewayRefsForHTTPRoute(httpRoute gatewayv1.HTTPRoute) []types.NamespacedName {
+	result := []types.NamespacedName{}
+	for _, gatewayRef := range httpRoute.Spec.ParentRefs {
+		namespace := httpRoute.GetNamespace()
+		if namespace == "" {
+			namespace = metav1.NamespaceDefault
+		}
+		if gatewayRef.Namespace != nil {
+			namespace = string(*gatewayRef.Namespace)
+		}
+
+		result = append(result, types.NamespacedName{
+			Namespace: namespace,
+			Name:      string(gatewayRef.Name),
+		})
+	}
+	return result
+}
+
+// FindGatewayClassNameForGateway returns GatewayClass for the Gateway.
+func FindGatewayClassNameForGateway(gateway gatewayv1.Gateway) string {
+	return string(gateway.Spec.GatewayClassName)
+}
+
+// FindBackendRefsForHTTPRoute returns Backends which the HTTPRoute references.
+func FindBackendRefsForHTTPRoute(httpRoute gatewayv1.HTTPRoute) []ObjRef {
+	// Aggregate all BackendRefs
+	var backendRefs []gatewayv1.BackendObjectReference
+	for _, rule := range httpRoute.Spec.Rules {
+		for _, backendRef := range rule.BackendRefs {
+			backendRefs = append(backendRefs, backendRef.BackendObjectReference)
+		}
+		for _, filter := range rule.Filters {
+			if filter.Type != gatewayv1.HTTPRouteFilterRequestMirror {
+				continue
+			}
+			if filter.RequestMirror == nil {
+				continue
+			}
+			backendRefs = append(backendRefs, filter.RequestMirror.BackendRef)
+		}
+	}
+
+	// Convert each BackendRef to ObjRef. ObjRef does not use pointers and thus is
+	// easily comparable.
+	resultSet := make(map[ObjRef]bool)
+	for _, backendRef := range backendRefs {
+		objRef := ObjRef{
+			Name: string(backendRef.Name),
+			// Assume namespace is unspecified in the backendRef and check later to
+			// override the default value.
+			Namespace: httpRoute.GetNamespace(),
+		}
+		if backendRef.Group != nil {
+			objRef.Group = string(*backendRef.Group)
+		}
+		if backendRef.Kind != nil {
+			objRef.Kind = string(*backendRef.Kind)
+		}
+		if backendRef.Namespace != nil {
+			objRef.Namespace = string(*backendRef.Namespace)
+		}
+		resultSet[objRef] = true
+	}
+
+	// Return unique objRefs
+	var result []ObjRef
+	for objRef := range resultSet {
+		result = append(result, objRef)
+	}
+	return result
+}