package metrics

import (
	"sync"

	"github.com/prometheus/client_golang/prometheus"
)

const billingSubsystem = "billing"

const (
	userRequestsMetric = "user_requests"
	userTrafficMetric  = "user_traffic"
)

type RequestType int

const (
	UNKNOWNRequest RequestType = iota
	HEADRequest    RequestType = iota
	PUTRequest     RequestType = iota
	LISTRequest    RequestType = iota
	GETRequest     RequestType = iota
	DELETERequest  RequestType = iota
)

func (t RequestType) String() string {
	switch t {
	case 1:
		return "HEAD"
	case 2:
		return "PUT"
	case 3:
		return "LIST"
	case 4:
		return "GET"
	case 5:
		return "DELETE"
	default:
		return "Unknown"
	}
}

type TrafficType int

const (
	UnknownTraffic TrafficType = iota
	INTraffic      TrafficType = iota
	OUTTraffic     TrafficType = iota
)

func (t TrafficType) String() string {
	switch t {
	case 1:
		return "IN"
	case 2:
		return "OUT"
	default:
		return "Unknown"
	}
}

type (
	OperationList [6]int

	UsersAPIStats struct {
		users map[string]*userAPIStats
		sync.RWMutex
	}

	bucketKey struct {
		name      string
		cid       string
		namespace string
	}

	bucketStat struct {
		Operations OperationList
		InTraffic  uint64
		OutTraffic uint64
	}

	userAPIStats struct {
		buckets map[bucketKey]bucketStat
		user    string
	}

	UserBucketInfo struct {
		User        string
		Bucket      string
		ContainerID string
		Namespace   string
	}

	UserMetricsInfo struct {
		UserBucketInfo
		Operation RequestType
		Requests  int
	}

	UserTrafficMetricsInfo struct {
		UserBucketInfo
		Type  TrafficType
		Value uint64
	}

	UserMetrics struct {
		Requests []UserMetricsInfo
		Traffic  []UserTrafficMetricsInfo
	}
)

func (u *UsersAPIStats) Update(user, bucket, cnrID, ns string, reqType RequestType, in, out uint64) {
	if u == nil {
		return
	}

	u.Lock()
	defer u.Unlock()

	usersStat := u.users[user]
	if usersStat == nil {
		if u.users == nil {
			u.users = make(map[string]*userAPIStats)
		}
		usersStat = &userAPIStats{
			buckets: make(map[bucketKey]bucketStat, 1),
			user:    user,
		}
		u.users[user] = usersStat
	}

	key := bucketKey{
		name:      bucket,
		cid:       cnrID,
		namespace: ns,
	}

	bktStat := usersStat.buckets[key]
	bktStat.Operations[reqType]++
	bktStat.InTraffic += in
	bktStat.OutTraffic += out
	usersStat.buckets[key] = bktStat
}

func (u *UsersAPIStats) DumpMetrics() UserMetrics {
	if u == nil {
		return UserMetrics{}
	}

	u.Lock()
	defer u.Unlock()

	result := UserMetrics{
		Requests: make([]UserMetricsInfo, 0, len(u.users)),
		Traffic:  make([]UserTrafficMetricsInfo, 0, len(u.users)),
	}

	for user, userStat := range u.users {
		for key, bktStat := range userStat.buckets {
			userBktInfo := UserBucketInfo{
				User:        user,
				Bucket:      key.name,
				ContainerID: key.cid,
				Namespace:   key.namespace,
			}

			if bktStat.InTraffic != 0 {
				result.Traffic = append(result.Traffic, UserTrafficMetricsInfo{
					UserBucketInfo: userBktInfo,
					Type:           INTraffic,
					Value:          bktStat.InTraffic,
				})
			}

			if bktStat.OutTraffic != 0 {
				result.Traffic = append(result.Traffic, UserTrafficMetricsInfo{
					UserBucketInfo: userBktInfo,
					Type:           OUTTraffic,
					Value:          bktStat.OutTraffic,
				})
			}

			for op, val := range bktStat.Operations {
				if val != 0 {
					result.Requests = append(result.Requests, UserMetricsInfo{
						UserBucketInfo: userBktInfo,
						Operation:      RequestType(op),
						Requests:       val,
					})
				}
			}
		}
	}

	u.users = make(map[string]*userAPIStats)

	return result
}

type billingMetrics struct {
	registry *prometheus.Registry

	userRequestsDesc *prometheus.Desc
	userTrafficDesc  *prometheus.Desc
	apiStat          *UsersAPIStats
}

func newBillingMetrics() *billingMetrics {
	return &billingMetrics{
		registry:         prometheus.NewRegistry(),
		userRequestsDesc: newDesc(appMetricsDesc[billingSubsystem][userRequestsMetric]),
		userTrafficDesc:  newDesc(appMetricsDesc[billingSubsystem][userTrafficMetric]),
		apiStat:          &UsersAPIStats{},
	}
}

func (b *billingMetrics) Gatherer() prometheus.Gatherer {
	return b.registry
}

func (b *billingMetrics) Register() {
	b.registry.MustRegister(b)
}

func (b *billingMetrics) Unregister() {
	b.registry.Unregister(b)
}

func (b *billingMetrics) Describe(ch chan<- *prometheus.Desc) {
	ch <- b.userRequestsDesc
	ch <- b.userTrafficDesc
}

func (b *billingMetrics) Collect(ch chan<- prometheus.Metric) {
	userMetrics := b.apiStat.DumpMetrics()

	for _, value := range userMetrics.Requests {
		ch <- prometheus.MustNewConstMetric(
			b.userRequestsDesc,
			prometheus.CounterValue,
			float64(value.Requests),
			value.User,
			value.Bucket,
			value.ContainerID,
			value.Operation.String(),
			value.Namespace,
		)
	}

	for _, value := range userMetrics.Traffic {
		ch <- prometheus.MustNewConstMetric(
			b.userTrafficDesc,
			prometheus.CounterValue,
			float64(value.Value),
			value.User,
			value.Bucket,
			value.ContainerID,
			value.Type.String(),
			value.Namespace,
		)
	}
}