// 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
		}
	}
	// Failed 2 updates one of which was with the latest controller, return the update error
	return
}

// 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) string {
	// Get all replication controllers.
	// TODO this needs a namespace scope as argument
	rcs, err := c.List(labels.Everything())
	if err != nil {
		glog.Fatalf("Error getting replication controllers: %v\n", 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)
		}
	}

	// Format the matching RC's into strings.
	var rcStrings []string
	for _, controller := range matchingRCs {
		rcStrings = append(rcStrings, fmt.Sprintf("%s (%d/%d replicas created)", controller.Name, controller.Status.Replicas, controller.Spec.Replicas))
	}

	list := strings.Join(rcStrings, ", ")
	if list == "" {
		return "<none>"
	}
	return list
}

// 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
}

// 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
}

// 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 controller.Status.Replicas == numReplicas {
		return nil
	}
	var getErr error
	glog.V(4).Infof("Updating replica count for rc: %v, %d->%d", controller.Name, controller.Status.Replicas, numReplicas)
	for i, rc := 0, &controller; ; i++ {
		rc.Status.Replicas = numReplicas
		_, updateErr = rcClient.Update(rc)
		if updateErr == nil || i >= updateRetries {
			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
		}
	}
	// Failed 2 updates one of which was with the latest controller, return the update error
	return
}