func newClient() (dynamic.Interface, error) {
	config, err := rest.InClusterConfig()
	if err != nil {
		return nil, err
	}

	dynClient, err := dynamic.NewForConfig(config)
	if err != nil {
		return nil, err
	}

	return dynClient, nil
}

var monboDBResource = schema.GroupVersionResource{Group: "mongodbcommunity.mongodb.com", Version: "v1", Resource: "mongodbcommunity"}

func ListMongoDB(ctx context.Context, client dynamic.Interface, namespace string) ([]unstructured.Unstructured, error)  {
	// GET /apis/mongodbcommunity.mongodb.com/v1/namespaces/{namespace}/mongodbcommunity/
	list, err := client.Resource(monboDBResource).Namespace(namespace).List(ctx, metav1.ListOptions{})
	if err != nil {
		return nil, err
	}

	return list.Items, nil
}

// ScaleMongoDB changes the number of members by the given proportion,
// which should be 0 =< proportion < 1.
func ScaleMongoDB(ctx context.Context, client dynamic.Interface, name string, namespace string, proportion uint) error {
	if proportion > 1 {
		return fmt.Errorf("proportion should be between 0 =< proportion < 1")
	}

	mongoDBClient := client.Resource(monboDBResource).Namespace(namespace)
	mdb, err := mongoDBClient.Get(ctx, name, metav1.GetOptions{})
	if err != nil {
		return err
	}

	members, found, err := unstructured.NestedInt64(mdb.UnstructuredContent(), "spec", "members")
	if err != nil {
		return err
	}

	if !found {
		return fmt.Errorf("members field not found on MongoDB spec")
	}

	scaled := int(members) * (1 + int(proportion))

	patch := []interface{}{
		map[string]interface{}{
			"op":    "replace",
			"path":  "/spec/members",
			"value": scaled,
		},
	}

	payload, err := json.Marshal(patch)
	if err != nil {
		return err
	}

	_, err = mongoDBClient.Patch(ctx, name, types.JSONPatchType, payload, metav1.PatchOptions{})
	if err != nil {
		return err
	}

	return nil
}

package main

import (
	"fmt"
	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
	"k8s.io/apimachinery/pkg/util/wait"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/dynamic/dynamicinformer"
	"k8s.io/client-go/tools/cache"
	"k8s.io/client-go/util/workqueue"
	"time"
)

const maxRetries = 3

var monboDBResource = schema.GroupVersionResource{Group: "mongodbcommunity.mongodb.com", Version: "v1", Resource: "mongodbcommunity"}

type MongoDBController struct {
	informer cache.SharedIndexInformer
	stopper  chan struct{}
	queue    workqueue.RateLimitingInterface
}

func NewMongoDBController(client dynamic.Interface) (*MongoDBController, error) {
	dynInformer := dynamicinformer.NewDynamicSharedInformerFactory(client, 0)
	informer := dynInformer.ForResource(monboDBResource).Informer()
	stopper := make(chan struct{})

	queue := workqueue.NewRateLimitingQueue(workqueue.DefaultControllerRateLimiter())
	informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
		DeleteFunc: func(obj interface{}) {
			key, err := cache.DeletionHandlingMetaNamespaceKeyFunc(obj)
			if err == nil {
				queue.Add(key)
			}
		},
	})

	return &MongoDBController{
		informer: informer,
		queue: queue,
		stopper: stopper,
	}, nil
}

func (m *MongoDBController) Stop() {
	close(m.stopper)
}

func (m *MongoDBController) Run() {
	defer utilruntime.HandleCrash()

	defer m.queue.ShutDown()

	go m.informer.Run(m.stopper)

	// wait for the caches to synchronize before starting the worker
	if !cache.WaitForCacheSync(m.stopper, m.informer.HasSynced) {
		utilruntime.HandleError(fmt.Errorf("timed out waiting for caches to sync"))
		return
	}

	// runWorker will loop until some problem happens. The wait.Until will then restart the worker after one second
	wait.Until(m.runWorker, time.Second, m.stopper)
}

func (m *MongoDBController) runWorker() {
	for {
		key, quit := m.queue.Get()
		if quit {
			return
		}

		err := m.processItem(key.(string))

		if err == nil {
			m.queue.Forget(key)
		} else if m.queue.NumRequeues(key) < maxRetries {
			m.queue.AddRateLimited(key)
		} else {
			m.queue.Forget(key)
			utilruntime.HandleError(err)
		}

		m.queue.Done(key)
	}
}

func (m *MongoDBController) processItem(mongodb string) error {
	// Clean up PVCs
	return nil
}

package main

import (
	"context"
	"k8s.io/apimachinery/pkg/runtime"
	dynamicfake "k8s.io/client-go/dynamic/fake"
)

func TestDynamicClient(t *testing.T) {
	// Setup an Object as mock on the client
	// Write it like its YAML manifest
	mdb := &unstructured.Unstructured{}
	mdb.SetUnstructuredContent(map[string]interface{}{
		"apiVersion": "mongodbcommunity.mongodb.com/v1",
		"kind": "MongoDBCommunity",
		"metadata": map[string]interface{} {
			"name":      "mongodb-test",
			"namespace": "default",
		},
		"spec": map[string]interface{}{
			"members": 3,
		},
	})

	dynamicClient := dynamicfake.NewSimpleDynamicClient(runtime.NewScheme(), mdb)

	// Run any logic that depend on the dynamic client
  NotifyMongoDBs(context.Background(), dynamicClient)

	AssertActions(t,  dynamicClient.Actions(), []ExpectedAction{
		{
			Verb: "list",
			Namespace: "default",
			Resource: "mongodbcommunity",
		},
	})

}

type ExpectedAction struct {
	Verb string
	Name string
	Namespace string
	Resource string

	// Patch action
	PatchType types.PatchType
	PatchPayload []map[string]interface{}
}

func AssertActions(t *testing.T, got []kubetesting.Action, expected []ExpectedAction) {
	if len(expected) > len(got) {
		t.Fatalf("executed actions too short, expected %d, got %d", len(expected), len(got))
		return
	}

	for i, expectedAction := range expected {
		if !AssertExpectedAction(got, expectedAction) {
			t.Fatalf("action %d does not match any of the got actions", i)
		}
	}
}

func AssertExpectedAction(got []kubetesting.Action, expectedAction ExpectedAction) bool {
	for _, gotAction := range got {
		switch expectedAction.Verb {
		case "get":
			getAction, ok := gotAction.(kubetesting.GetAction)
			if !ok {
				continue
			}

			if getAction.GetName() != expectedAction.Name {
				continue
			}

			if !validateNamespaceAndResource(getAction, expectedAction) {
				continue
			}

			return true
		case "list":
			listAction, ok := gotAction.(kubetesting.ListAction)
			if !ok {
				continue
			}

			if !validateNamespaceAndResource(listAction, expectedAction) {
				continue
			}

			return true
		case "watch":
			watchAction, ok := gotAction.(kubetesting.WatchAction)
			if !ok {
				continue
			}

			if !validateNamespaceAndResource(watchAction, expectedAction) {
				continue
			}

			return true
		case "create":
			createAction, ok := gotAction.(kubetesting.CreateAction)
			if !ok {
				continue
			}

			if !validateNamespaceAndResource(createAction, expectedAction) {
				continue
			}

			return true
		case "update":
			updateAction, ok := gotAction.(kubetesting.UpdateAction)
			if !ok {
				continue
			}

			if !validateNamespaceAndResource(updateAction, expectedAction) {
				continue
			}

			return true
		case "delete":
			deleteAction, ok := gotAction.(kubetesting.DeleteAction)
			if !ok {
				continue
			}

			if deleteAction.GetName() != expectedAction.Name {
				continue
			}

			if !validateNamespaceAndResource(deleteAction, expectedAction) {
				continue
			}

			return true
		case "patch":
			patchAction, ok := gotAction.(kubetesting.PatchAction)
			if !ok {
				continue
			}

			if patchAction.GetName() != expectedAction.Name {
				continue
			}

			if !validateNamespaceAndResource(patchAction, expectedAction) {
				continue
			}

			if patchAction.GetPatchType() != expectedAction.PatchType {
				continue
			}

			patchBytes, err := json.Marshal(expectedAction.PatchPayload)
			if err != nil {
				continue
			}

			if !bytes.Equal(patchAction.GetPatch(), patchBytes) {
				continue
			}

			return true
		}
	}

	return false
}

func validateNamespaceAndResource(action kubetesting.Action, expectedAction ExpectedAction) bool {
	return action.GetNamespace() == expectedAction.Namespace && action.GetResource().Resource == expectedAction.Resource
}