/*
Copyright 2019 The Kubernetes Authors.

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.
*/

package core

import (
	"reflect"

	apiv1 "k8s.io/api/core/v1"
	apiequality "k8s.io/apimachinery/pkg/api/equality"
	"k8s.io/apimachinery/pkg/types"
	"k8s.io/autoscaler/cluster-autoscaler/processors/status"
	"k8s.io/autoscaler/cluster-autoscaler/utils/drain"
)

type podEquivalenceGroup struct {
	pods             []*apiv1.Pod
	schedulingErrors map[string]status.Reasons
	schedulable      bool
}

// buildPodEquivalenceGroups prepares pod groups with equivalent scheduling properties.
func buildPodEquivalenceGroups(pods []*apiv1.Pod) []*podEquivalenceGroup {
	podEquivalenceGroups := []*podEquivalenceGroup{}
	for _, pods := range groupPodsBySchedulingProperties(pods) {
		podEquivalenceGroups = append(podEquivalenceGroups, &podEquivalenceGroup{
			pods:             pods,
			schedulingErrors: map[string]status.Reasons{},
			schedulable:      false,
		})
	}
	return podEquivalenceGroups
}

type equivalenceGroupId int
type equivalenceGroup struct {
	id           equivalenceGroupId
	representant *apiv1.Pod
}

// groupPodsBySchedulingProperties groups pods based on scheduling properties. Group ID is meaningless.
func groupPodsBySchedulingProperties(pods []*apiv1.Pod) map[equivalenceGroupId][]*apiv1.Pod {
	podEquivalenceGroups := map[equivalenceGroupId][]*apiv1.Pod{}
	equivalenceGroupsByController := make(map[types.UID][]equivalenceGroup)

	var nextGroupId equivalenceGroupId
	for _, pod := range pods {
		controllerRef := drain.ControllerRef(pod)
		if controllerRef == nil {
			podEquivalenceGroups[nextGroupId] = []*apiv1.Pod{pod}
			nextGroupId++
			continue
		}

		matchingFound := false
		for _, g := range equivalenceGroupsByController[controllerRef.UID] {
			if reflect.DeepEqual(pod.Labels, g.representant.Labels) && apiequality.Semantic.DeepEqual(pod.Spec, g.representant.Spec) {
				matchingFound = true
				podEquivalenceGroups[g.id] = append(podEquivalenceGroups[g.id], pod)
				break
			}
		}

		if !matchingFound {
			newGroup := equivalenceGroup{
				id:           nextGroupId,
				representant: pod,
			}
			equivalenceGroupsByController[controllerRef.UID] = append(equivalenceGroupsByController[controllerRef.UID], newGroup)
			podEquivalenceGroups[newGroup.id] = append(podEquivalenceGroups[newGroup.id], pod)
			nextGroupId++
		}
	}

	return podEquivalenceGroups
}