/*
Copyright 2017 The Kubernetes Authors.
Copyright 2020 Authors of Arktos - file modified.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// NOTE: DO NOT use those helper functions through client-go, the
// package path will be changed in the future.
package qos

import (
	"k8s.io/apimachinery/pkg/api/resource"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/kubernetes/pkg/apis/core"
)

var supportedQoSComputeResources = sets.NewString(string(core.ResourceCPU), string(core.ResourceMemory))

func isSupportedQoSComputeResource(name core.ResourceName) bool {
	return supportedQoSComputeResources.Has(string(name))
}

// GetPodQOS returns the QoS class of a pod.
// A pod is besteffort if none of its containers have specified any requests or limits.
// A pod is guaranteed only when requests and limits are specified for all the containers and they are equal.
// A pod is burstable if limits and requests do not match across all containers.
func GetPodQOS(pod *core.Pod) core.PodQOSClass {
	requests := core.ResourceList{}
	limits := core.ResourceList{}
	zeroQuantity := resource.MustParse("0")
	isGuaranteed := true

	// Since pod.Spec.Workload() can potentially change the spec.WorkloadInfo slice in the pod
	// make a local copy for calculate the QoS class for a given pod, instead lock the function
	// for possible perf impact
	specLocal := pod.Spec.DeepCopy()

	for _, workload := range specLocal.Workloads() {
		// process requests
		for name, quantity := range workload.Resources.Requests {
			if !isSupportedQoSComputeResource(name) {
				continue
			}
			if quantity.Cmp(zeroQuantity) == 1 {
				delta := quantity.Copy()
				if _, exists := requests[name]; !exists {
					requests[name] = *delta
				} else {
					delta.Add(requests[name])
					requests[name] = *delta
				}
			}
		}
		// process limits
		qosLimitsFound := sets.NewString()
		for name, quantity := range workload.Resources.Limits {
			if !isSupportedQoSComputeResource(name) {
				continue
			}
			if quantity.Cmp(zeroQuantity) == 1 {
				qosLimitsFound.Insert(string(name))
				delta := quantity.Copy()
				if _, exists := limits[name]; !exists {
					limits[name] = *delta
				} else {
					delta.Add(limits[name])
					limits[name] = *delta
				}
			}
		}

		if !qosLimitsFound.HasAll(string(core.ResourceMemory), string(core.ResourceCPU)) {
			isGuaranteed = false
		}
	}
	if len(requests) == 0 && len(limits) == 0 {
		return core.PodQOSBestEffort
	}
	// Check is requests match limits for all resources.
	if isGuaranteed {
		for name, req := range requests {
			if lim, exists := limits[name]; !exists || lim.Cmp(req) != 0 {
				isGuaranteed = false
				break
			}
		}
	}
	if isGuaranteed &&
		len(requests) == len(limits) {
		return core.PodQOSGuaranteed
	}
	return core.PodQOSBurstable
}
