// updateReplicaCount attempts to update the Status.Replicas of the given controller, with a single GET/PUT retry.
func updateReplicaCount(rcClient client.ReplicationControllerInterface, controller api.ReplicationController, numReplicas int) (updateErr error) {
	// This is the steady state. It happens when the rc doesn't have any expectations, since
	// we do a periodic relist every 30s. If the generations differ but the replicas are
	// the same, a caller might've resized to the same replica count.
	if controller.Status.Replicas == numReplicas &&
		controller.Generation == controller.Status.ObservedGeneration {
		return nil
	}
	// Save the generation number we acted on, otherwise we might wrongfully indicate
	// that we've seen a spec update when we retry.
	// TODO: This can clobber an update if we allow multiple agents to write to the
	// same status.
	generation := controller.Generation

	var getErr error
	for i, rc := 0, &controller; ; i++ {
		glog.V(4).Infof("Updating replica count for rc: %v, %d->%d (need %d), sequence No: %v->%v",
			controller.Name, controller.Status.Replicas, numReplicas, controller.Spec.Replicas, controller.Status.ObservedGeneration, generation)

		rc.Status = api.ReplicationControllerStatus{Replicas: numReplicas, ObservedGeneration: generation}
		_, updateErr = rcClient.Update(rc)
		if updateErr == nil || i >= statusUpdateRetries {
			return updateErr
		}
		// Update the controller with the latest resource version for the next poll
		if rc, getErr = rcClient.Get(controller.Name); getErr != nil {
			// If the GET fails we can't trust status.Replicas anymore. This error
			// is bound to be more interesting than the update failure.
			return getErr
		}
	}
}

// getOverlappingControllers finds rcs that this controller overlaps, as well as rcs overlapping this controller.
func getOverlappingControllers(c client.ReplicationControllerInterface, rc *api.ReplicationController) ([]api.ReplicationController, error) {
	rcs, err := c.List(labels.Everything())
	if err != nil {
		return nil, fmt.Errorf("error getting replication controllers: %v", err)
	}
	var matchingRCs []api.ReplicationController
	rcLabels := labels.Set(rc.Spec.Selector)
	for _, controller := range rcs.Items {
		newRCLabels := labels.Set(controller.Spec.Selector)
		if labels.SelectorFromSet(newRCLabels).Matches(rcLabels) || labels.SelectorFromSet(rcLabels).Matches(newRCLabels) {
			matchingRCs = append(matchingRCs, controller)
		}
	}
	return matchingRCs, nil
}

// WaitForADeployment waits for a Deployment to fulfill the isOK function
func WaitForADeployment(client kclient.ReplicationControllerInterface,
	name string,
	isOK, isFailed func(*kapi.ReplicationController) bool) error {
	for {
		requirement, err := labels.NewRequirement(deployapi.DeploymentConfigAnnotation, labels.EqualsOperator, kutil.NewStringSet(name))
		if err != nil {
			return fmt.Errorf("unexpected error generating label selector: %v", err)
		}

		list, err := client.List(labels.LabelSelector{*requirement})
		if err != nil {
			return err
		}
		for i := range list.Items {
			if isOK(&list.Items[i]) {
				return nil
			}
			if isFailed(&list.Items[i]) {
				return fmt.Errorf("The deployment %q status is %q",
					name, list.Items[i].Annotations[deployapi.DeploymentStatusAnnotation])
			}
		}

		rv := list.ResourceVersion
		w, err := client.Watch(labels.LabelSelector{*requirement}, fields.Everything(), rv)
		if err != nil {
			return err
		}
		defer w.Stop()

		for {
			val, ok := <-w.ResultChan()
			if !ok {
				// reget and re-watch
				break
			}
			if e, ok := val.Object.(*kapi.ReplicationController); ok {
				if isOK(e) {
					return nil
				}
				if isFailed(e) {
					return fmt.Errorf("The deployment %q status is %q",
						name, e.Annotations[deployapi.DeploymentStatusAnnotation])
				}
			}
		}
	}
}

// Get all replication controllers whose selectors would match a given set of
// labels.
// TODO Move this to pkg/client and ideally implement it server-side (instead
// of getting all RC's and searching through them manually).
func getReplicationControllersForLabels(c client.ReplicationControllerInterface, labelsToMatch labels.Labels) ([]api.ReplicationController, error) {
	// Get all replication controllers.
	// TODO this needs a namespace scope as argument
	rcs, err := c.List(labels.Everything())
	if err != nil {
		return nil, fmt.Errorf("error getting replication controllers: %v", err)
	}

	// Find the ones that match labelsToMatch.
	var matchingRCs []api.ReplicationController
	for _, controller := range rcs.Items {
		selector := labels.SelectorFromSet(controller.Spec.Selector)
		if selector.Matches(labelsToMatch) {
			matchingRCs = append(matchingRCs, controller)
		}
	}
	return matchingRCs, nil
}

// updateWithRetries updates applies the given rc as an update.
func updateWithRetries(rcClient client.ReplicationControllerInterface, rc *api.ReplicationController, applyUpdate updateFunc) (*api.ReplicationController, error) {
	var err error
	oldRc := rc
	err = wait.Poll(10*time.Millisecond, 1*time.Minute, func() (bool, error) {
		// Apply the update, then attempt to push it to the apiserver.
		applyUpdate(rc)
		if rc, err = rcClient.Update(rc); err == nil {
			// rc contains the latest controller post update
			return true, nil
		}
		// Update the controller with the latest resource version, if the update failed we
		// can't trust rc so use oldRc.Name.
		if rc, err = rcClient.Get(oldRc.Name); err != nil {
			// The Get failed: Value in rc cannot be trusted.
			rc = oldRc
		}
		// The Get passed: rc contains the latest controller, expect a poll for the update.
		return false, nil
	})
	// If the error is non-nil the returned controller cannot be trusted, if it is nil, the returned
	// controller contains the applied update.
	return rc, err
}