package npm

import (
	"fmt"
	"sort"
	"container/heap"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

	"github.com/Azure/azure-container-networking/log"
	"github.com/Azure/azure-container-networking/npm/util"
)

// An ReqHeap is a min-heap of labelSelectorRequirements.
type ReqHeap []metav1.LabelSelectorRequirement

func (h ReqHeap) Len() int { 
	return len(h)
}

func (h ReqHeap) Less(i, j int) bool {
	sort.Strings(h[i].Values)
	sort.Strings(h[j].Values)
	
	if int(h[i].Key[0]) < int(h[j].Key[0]) {
		return true
	}
	
	if int(h[i].Key[0]) > int(h[j].Key[0]) {
		return false
	}

	if len(h[i].Values) == 0 {
		return true
	}

	if len(h[j].Values) == 0 {
		return false
	}
	
	if len(h[i].Values[0]) == 0 {
		return true
	}

	if len(h[j].Values[0]) == 0 {
		return false
	}

	return int(h[i].Values[0][0]) < int(h[j].Values[0][0])
}

func (h ReqHeap) Swap(i, j int) {
	h[i], h[j] = h[j], h[i]
}

func (h *ReqHeap) Push(x interface{}) {
	sort.Strings(x.(metav1.LabelSelectorRequirement).Values)
	*h = append(*h, x.(metav1.LabelSelectorRequirement))
}

func (h *ReqHeap) Pop() interface{} {
	old := *h
	n := len(old)
	x := old[n -1]
	*h = old[0 : n - 1]

	return x
}

// ParseLabel takes a Azure-NPM processed label then returns if it's referring to complement set,
// and if so, returns the original set as well.
func ParseLabel(label string) (string, bool) {
	//The input label is guaranteed to have a non-zero length validated by k8s.
	//For label definition, see below parseSelector() function.
	if label[0:1] == util.IptablesNotFlag {
		return label[1:], true
	}
	return label, false
}

// GetOperatorAndLabel returns the operator associated with the label and the label without operator.
func GetOperatorAndLabel(label string) (string, string) {
	if len(label) == 0 {
		return "", ""
	}

	if string(label[0]) == util.IptablesNotFlag {
		return util.IptablesNotFlag, label[1:]
	}

	return "", label
}

// GetOperatorsAndLabels returns the operators along with the associated labels.
func GetOperatorsAndLabels(labelsWithOps []string) ([]string, []string) {
	var ops, labelsWithoutOps []string
	for _, labelWithOp := range labelsWithOps {
		op, labelWithoutOp := GetOperatorAndLabel(labelWithOp)
		ops = append(ops, op)
		labelsWithoutOps = append(labelsWithoutOps, labelWithoutOp)
	}

	return ops, labelsWithoutOps
}

// sortSelector sorts the member fields of the selector in an alphebatical order.
func sortSelector(selector *metav1.LabelSelector) {
	_, _ = util.SortMap(&selector.MatchLabels)

	reqHeap := &ReqHeap{}
	heap.Init(reqHeap)
	for _, req := range selector.MatchExpressions {
		heap.Push(reqHeap, req)
	}

	var sortedReqs []metav1.LabelSelectorRequirement
	for reqHeap.Len() > 0 {
		sortedReqs = append(sortedReqs, heap.Pop(reqHeap).(metav1.LabelSelectorRequirement))

	}
	selector.MatchExpressions = sortedReqs
}

// HashSelector returns the hash value of the selector.
func HashSelector(selector *metav1.LabelSelector) string {
	sortSelector(selector)
	return util.Hash(fmt.Sprintf("%v", selector))
}

// parseSelector takes a LabelSelector and returns a slice of processed labels, keys and values.
func parseSelector(selector *metav1.LabelSelector) ([]string, []string, []string) {
	var (
		labels []string
		keys   []string
		vals   []string
	)

	if selector == nil {
		return labels, keys, vals
	}

	if len(selector.MatchLabels) == 0 && len(selector.MatchExpressions) == 0 {
		labels = append(labels, "")
		keys = append(keys, "")
		vals = append(vals, "")

		return labels, keys, vals
	}

	sortedKeys, sortedVals := util.SortMap(&selector.MatchLabels)

	for i := range sortedKeys {
		labels = append(labels, sortedKeys[i]+":"+sortedVals[i])
	}
	keys = append(keys, sortedKeys...)
	vals = append(vals, sortedVals...)

	for _, req := range selector.MatchExpressions {
		var k string
		switch op := req.Operator; op {
		case metav1.LabelSelectorOpIn:
			for _, v := range req.Values {
				k = req.Key
				keys = append(keys, k)
				vals = append(vals, v)
				labels = append(labels, k+":"+v)
			}
		case metav1.LabelSelectorOpNotIn:
			for _, v := range req.Values {
				k = util.IptablesNotFlag + req.Key
				keys = append(keys, k)
				vals = append(vals, v)
				labels = append(labels, k+":"+v)
			}
		// Exists matches pods with req.Key as key
		case metav1.LabelSelectorOpExists:
			k = req.Key
			keys = append(keys, req.Key)
			vals = append(vals, "")
			labels = append(labels, k)
		// DoesNotExist matches pods without req.Key as key
		case metav1.LabelSelectorOpDoesNotExist:
			k = util.IptablesNotFlag + req.Key
			keys = append(keys, k)
			vals = append(vals, "")
			labels = append(labels, k)
		default:
			log.Errorf("Invalid operator [%s] for selector [%v] requirement", op, *selector)
		}
	}

	return labels, keys, vals
}