first lookup template function implementation

Signed-off-by: raffaelespazzoli <raffaele.spazzoli@gmail.com>

pkg/engine/funcs.go

@@ -53,6 +53,7 @@ func funcMap() template.FuncMap {
 		"fromYaml": fromYAML,
 		"toJson":   toJSON,
 		"fromJson": fromJSON,
+		"lookup" : lookup,
 
 		// This is a placeholder for the "include" function, which is
 		// late-bound to a template. By declaring it here, we preserve the

pkg/engine/lookup_func.go

@@ -0,0 +1,118 @@
+package engine
+
+import (
+	"flag"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/dynamic"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/clientcmd"
+)
+
+var config *rest.Config
+var addLookupFunction = false
+
+func init() {
+	// try the out-cluster config, this will default to the in-cluster config is not successful
+	var kubeconfig *string
+	if home := homeDir(); home != "" {
+		kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
+	} else {
+		kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
+	}
+	flag.Parse()
+
+	// use the current context in kubeconfig
+	config1, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
+	if err == nil {
+		addLookupFunction = true
+		config = config1
+	}
+	return
+}
+
+func homeDir() string {
+	if h := os.Getenv("HOME"); h != "" {
+		return h
+	}
+	return os.Getenv("USERPROFILE") // windows
+}
+
+func lookup(apiversion string, resource string, namespace string, name string) (map[string]interface{}, error) {
+	var client dynamic.ResourceInterface
+	c, err := getDynamicClientOnKind(apiversion, resource)
+	if err != nil {
+		return map[string]interface{}{}, err
+	}
+	if namespace != "" {
+		client = c.Namespace(namespace)
+	} else {
+		client = c
+	}
+	if name != "" {
+		//this will return a single object
+		obj, err := client.Get(name, metav1.GetOptions{})
+		if err != nil {
+			return map[string]interface{}{}, err
+		}
+		return obj.Object, nil
+	}
+	//this will return a list
+	obj, err := client.List(metav1.ListOptions{})
+	if err != nil {
+		return map[string]interface{}{}, err
+	}
+	return obj.Object, nil
+
+}
+
+// GetDynamicClientOnUnstructured returns a dynamic client on an Unstructured type. This client can be further namespaced.
+func getDynamicClientOnKind(apiversion string, kind string) (dynamic.NamespaceableResourceInterface, error) {
+	gvk := schema.FromAPIVersionAndKind(apiversion, kind)
+	apiRes, err := getAPIReourceForGVK(gvk)
+	if err != nil {
+		log.Printf("[ERROR] unable to get apiresource from unstructured: %s , error %s", gvk.String(), err)
+		return nil, err
+	}
+	gvr := schema.GroupVersionResource{
+		Group:    apiRes.Group,
+		Version:  apiRes.Version,
+		Resource: apiRes.Name,
+	}
+	intf, err := dynamic.NewForConfig(config)
+	if err != nil {
+		log.Printf("[ERROR] unable to get dynamic client %s", err)
+		return nil, err
+	}
+	res := intf.Resource(gvr)
+	return res, nil
+}
+
+func getAPIReourceForGVK(gvk schema.GroupVersionKind) (metav1.APIResource, error) {
+	res := metav1.APIResource{}
+	discoveryClient, err := discovery.NewDiscoveryClientForConfig(config)
+	if err != nil {
+		log.Printf("[ERROR] unable to create discovery client %s", err)
+		return res, err
+	}
+	resList, err := discoveryClient.ServerResourcesForGroupVersion(gvk.GroupVersion().String())
+	if err != nil {
+		log.Printf("[ERROR] unable to retrieve resouce list for: %s , error: %s", gvk.GroupVersion().String(), err)
+		return res, err
+	}
+	for _, resource := range resList.APIResources {
+		if resource.Kind == gvk.Kind && !strings.Contains(resource.Name, "/") {
+			res = resource
+			res.Group = gvk.Group
+			res.Version = gvk.Version
+			break
+		}
+	}
+	return res, nil
+}