// CalculateNodeLabelPriority checks whether a particular label exists on a minion or not, regardless of its value.
// If presence is true, prioritizes minions that have the specified label, regardless of value.
// If presence is false, prioritizes minions that do not have the specified label.
func (n *NodeLabelPrioritizer) CalculateNodeLabelPriority(pod *api.Pod, podLister algorithm.PodLister, minionLister algorithm.MinionLister) (algorithm.HostPriorityList, error) {
	var score int
	minions, err := minionLister.List()
	if err != nil {
		return nil, err
	}

	labeledMinions := map[string]bool{}
	for _, minion := range minions.Items {
		exists := labels.Set(minion.Labels).Has(n.label)
		labeledMinions[minion.Name] = (exists && n.presence) || (!exists && !n.presence)
	}

	result := []algorithm.HostPriority{}
	//score int - scale of 0-10
	// 0 being the lowest priority and 10 being the highest
	for minionName, success := range labeledMinions {
		if success {
			score = 10
		} else {
			score = 0
		}
		result = append(result, algorithm.HostPriority{Host: minionName, Score: score})
	}
	return result, nil
}

func (g *genericScheduler) Schedule(pod *api.Pod, minionLister algorithm.MinionLister) (string, error) {
	minions, err := minionLister.List()
	if err != nil {
		return "", err
	}
	if len(minions.Items) == 0 {
		return "", ErrNoNodesAvailable
	}

	filteredNodes, failedPredicateMap, err := findNodesThatFit(pod, g.pods, g.predicates, minions)
	if err != nil {
		return "", err
	}

	priorityList, err := prioritizeNodes(pod, g.pods, g.prioritizers, algorithm.FakeMinionLister(filteredNodes))
	if err != nil {
		return "", err
	}
	if len(priorityList) == 0 {
		return "", &FitError{
			Pod:              pod,
			FailedPredicates: failedPredicateMap,
		}
	}

	return g.selectHost(priorityList)
}

// LeastRequestedPriority is a priority function that favors nodes with fewer requested resources.
// It calculates the percentage of memory and CPU requested by pods scheduled on the node, and prioritizes
// based on the minimum of the average of the fraction of requested to capacity.
// Details: (Sum(requested cpu) / Capacity + Sum(requested memory) / Capacity) * 50
func LeastRequestedPriority(pod *api.Pod, podLister algorithm.PodLister, minionLister algorithm.MinionLister) (algorithm.HostPriorityList, error) {
	nodes, err := minionLister.List()
	if err != nil {
		return algorithm.HostPriorityList{}, err
	}
	podsToMachines, err := predicates.MapPodsToMachines(podLister)

	list := algorithm.HostPriorityList{}
	for _, node := range nodes.Items {
		list = append(list, calculateOccupancy(pod, node, podsToMachines[node.Name]))
	}
	return list, nil
}

// BalancedResourceAllocation favors nodes with balanced resource usage rate.
// BalancedResourceAllocation should **NOT** be used alone, and **MUST** be used together with LeastRequestedPriority.
// It calculates the difference between the cpu and memory fracion of capacity, and prioritizes the host based on how
// close the two metrics are to each other.
// Detail: score = 10 - abs(cpuFraction-memoryFraction)*10. The algorithm is partly inspired by:
// "Wei Huang et al. An Energy Efficient Virtual Machine Placement Algorithm with Balanced Resource Utilization"
func BalancedResourceAllocation(pod *api.Pod, podLister algorithm.PodLister, minionLister algorithm.MinionLister) (algorithm.HostPriorityList, error) {
	nodes, err := minionLister.List()
	if err != nil {
		return algorithm.HostPriorityList{}, err
	}
	podsToMachines, err := predicates.MapPodsToMachines(podLister)

	list := algorithm.HostPriorityList{}
	for _, node := range nodes.Items {
		list = append(list, calculateBalancedResourceAllocation(pod, node, podsToMachines[node.Name]))
	}
	return list, nil
}

// CalculateSpreadPriority spreads pods by minimizing the number of pods belonging to the same service
// on the same machine.
func (s *ServiceSpread) CalculateSpreadPriority(pod *api.Pod, podLister algorithm.PodLister, minionLister algorithm.MinionLister) (algorithm.HostPriorityList, error) {
	var maxCount int
	var nsServicePods []*api.Pod

	services, err := s.serviceLister.GetPodServices(pod)
	if err == nil {
		// just use the first service and get the other pods within the service
		// TODO: a separate predicate can be created that tries to handle all services for the pod
		selector := labels.SelectorFromSet(services[0].Spec.Selector)
		pods, err := podLister.List(selector)
		if err != nil {
			return nil, err
		}
		// consider only the pods that belong to the same namespace
		for _, nsPod := range pods {
			if nsPod.Namespace == pod.Namespace {
				nsServicePods = append(nsServicePods, nsPod)
			}
		}
	}

	minions, err := minionLister.List()
	if err != nil {
		return nil, err
	}

	counts := map[string]int{}
	if len(nsServicePods) > 0 {
		for _, pod := range nsServicePods {
			counts[pod.Spec.NodeName]++
			// Compute the maximum number of pods hosted on any minion
			if counts[pod.Spec.NodeName] > maxCount {
				maxCount = counts[pod.Spec.NodeName]
			}
		}
	}

	result := []algorithm.HostPriority{}
	//score int - scale of 0-10
	// 0 being the lowest priority and 10 being the highest
	for _, minion := range minions.Items {
		// initializing to the default/max minion score of 10
		fScore := float32(10)
		if maxCount > 0 {
			fScore = 10 * (float32(maxCount-counts[minion.Name]) / float32(maxCount))
		}
		result = append(result, algorithm.HostPriority{Host: minion.Name, Score: int(fScore)})
	}
	return result, nil
}

// EqualPriority is a prioritizer function that gives an equal weight of one to all nodes
func EqualPriority(_ *api.Pod, podLister algorithm.PodLister, minionLister algorithm.MinionLister) (algorithm.HostPriorityList, error) {
	nodes, err := minionLister.List()
	if err != nil {
		fmt.Errorf("failed to list nodes: %v", err)
		return []algorithm.HostPriority{}, err
	}

	result := []algorithm.HostPriority{}
	for _, minion := range nodes.Items {
		result = append(result, algorithm.HostPriority{
			Host:  minion.Name,
			Score: 1,
		})
	}
	return result, nil
}

func numericPriority(pod *api.Pod, podLister algorithm.PodLister, minionLister algorithm.MinionLister) (algorithm.HostPriorityList, error) {
	nodes, err := minionLister.List()
	result := []algorithm.HostPriority{}

	if err != nil {
		return nil, fmt.Errorf("failed to list nodes: %v", err)
	}
	for _, minion := range nodes.Items {
		score, err := strconv.Atoi(minion.Name)
		if err != nil {
			return nil, err
		}
		result = append(result, algorithm.HostPriority{
			Host:  minion.Name,
			Score: score,
		})
	}
	return result, nil
}

// CalculateAntiAffinityPriority spreads pods by minimizing the number of pods belonging to the same service
// on machines with the same value for a particular label.
// The label to be considered is provided to the struct (ServiceAntiAffinity).
func (s *ServiceAntiAffinity) CalculateAntiAffinityPriority(pod *api.Pod, podLister algorithm.PodLister, minionLister algorithm.MinionLister) (algorithm.HostPriorityList, error) {
	var nsServicePods []*api.Pod

	services, err := s.serviceLister.GetPodServices(pod)
	if err == nil {
		// just use the first service and get the other pods within the service
		// TODO: a separate predicate can be created that tries to handle all services for the pod
		selector := labels.SelectorFromSet(services[0].Spec.Selector)
		pods, err := podLister.List(selector)
		if err != nil {
			return nil, err
		}
		// consider only the pods that belong to the same namespace
		for _, nsPod := range pods {
			if nsPod.Namespace == pod.Namespace {
				nsServicePods = append(nsServicePods, nsPod)
			}
		}
	}

	minions, err := minionLister.List()
	if err != nil {
		return nil, err
	}

	// separate out the minions that have the label from the ones that don't
	otherMinions := []string{}
	labeledMinions := map[string]string{}
	for _, minion := range minions.Items {
		if labels.Set(minion.Labels).Has(s.label) {
			label := labels.Set(minion.Labels).Get(s.label)
			labeledMinions[minion.Name] = label
		} else {
			otherMinions = append(otherMinions, minion.Name)
		}
	}

	podCounts := map[string]int{}
	for _, pod := range nsServicePods {
		label, exists := labeledMinions[pod.Spec.NodeName]
		if !exists {
			continue
		}
		podCounts[label]++
	}

	numServicePods := len(nsServicePods)
	result := []algorithm.HostPriority{}
	//score int - scale of 0-10
	// 0 being the lowest priority and 10 being the highest
	for minion := range labeledMinions {
		// initializing to the default/max minion score of 10
		fScore := float32(10)
		if numServicePods > 0 {
			fScore = 10 * (float32(numServicePods-podCounts[labeledMinions[minion]]) / float32(numServicePods))
		}
		result = append(result, algorithm.HostPriority{Host: minion, Score: int(fScore)})
	}
	// add the open minions with a score of 0
	for _, minion := range otherMinions {
		result = append(result, algorithm.HostPriority{Host: minion, Score: 0})
	}

	return result, nil
}