package metrics

import (
	"fmt"
	"sync"
	"time"

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

const (
	wcSubsystem = "writecache"
	wcShardID   = "shard_id"
	wcSuccess   = "success"
	wcStorage   = "storage"
	wcMode      = "mode"
)

type shardIDMode struct {
	shardID, mode string
}

type WriteCacheMetrics interface {
	AddGetDuration(shardID string, success bool, d time.Duration, storageType string)
	AddDeleteDuration(shardID string, success bool, d time.Duration, storageType string)
	AddPutDuration(shardID string, success bool, d time.Duration, storageType string)

	IncActualCount(shardID string, storageType string)
	DecActualCount(shardID string, storageType string)
	SetActualCount(shardID string, count uint64, storageType string)

	SetEstimateSize(shardID string, size uint64, storageType string)
	SetMode(shardID string, mode string)

	IncFlushCounter(shardID string, success bool, storageType string)
	IncEvictCounter(shardID string, storageType string)
}

type writeCacheMetrics struct {
	getDuration    metric[*prometheus.HistogramVec]
	putDuration    metric[*prometheus.HistogramVec]
	deleteDuration metric[*prometheus.HistogramVec]

	flushCounter metric[*prometheus.CounterVec]
	evictCounter metric[*prometheus.CounterVec]

	actualCount metric[*prometheus.GaugeVec]

	estimatedSize metric[*prometheus.GaugeVec]

	modeMetrics map[shardIDMode]metric[prometheus.GaugeFunc]
	modeValues  map[string]string
	modeMtx     sync.RWMutex
}

func newWriteCacheMetrics() *writeCacheMetrics {
	return &writeCacheMetrics{
		getDuration:    newWCMethodDurationCounter("get"),
		putDuration:    newWCMethodDurationCounter("put"),
		deleteDuration: newWCMethodDurationCounter("delete"),
		flushCounter:   newWCOperationCounterVec("flush", []string{wcShardID, wcStorage, wcSuccess}),
		evictCounter:   newWCOperationCounterVec("evict", []string{wcShardID, wcStorage}),
		actualCount:    newWCGaugeVec("actual_objects_count", "Actual objects count in writecache", []string{wcShardID, wcStorage}),
		estimatedSize:  newWCGaugeVec("estimated_size_bytes", "Estimated writecache size", []string{wcShardID, wcStorage}),
		modeMtx:        sync.RWMutex{},
		modeMetrics:    make(map[shardIDMode]metric[prometheus.GaugeFunc]),
		modeValues:     make(map[string]string),
	}
}

func (m *writeCacheMetrics) AddGetDuration(shardID string, success bool, d time.Duration, storageType string) {
	setWriteCacheDuration(m.getDuration.value, shardID, success, d, storageType)
}

func (m *writeCacheMetrics) AddDeleteDuration(shardID string, success bool, d time.Duration, storageType string) {
	setWriteCacheDuration(m.deleteDuration.value, shardID, success, d, storageType)
}

func (m *writeCacheMetrics) AddPutDuration(shardID string, success bool, d time.Duration, storageType string) {
	setWriteCacheDuration(m.putDuration.value, shardID, success, d, storageType)
}

func (m *writeCacheMetrics) IncActualCount(shardID string, storageType string) {
	m.actualCount.value.With(prometheus.Labels{
		wcShardID: shardID,
		wcStorage: storageType,
	}).Inc()
}

func (m *writeCacheMetrics) DecActualCount(shardID string, storageType string) {
	m.actualCount.value.With(prometheus.Labels{
		wcShardID: shardID,
		wcStorage: storageType,
	}).Dec()
}

func (m *writeCacheMetrics) SetActualCount(shardID string, count uint64, storageType string) {
	m.actualCount.value.With(prometheus.Labels{
		wcShardID: shardID,
		wcStorage: storageType,
	}).Set(float64(count))
}

func (m *writeCacheMetrics) SetEstimateSize(shardID string, size uint64, storageType string) {
	m.estimatedSize.value.With(prometheus.Labels{
		wcShardID: shardID,
		wcStorage: storageType,
	}).Set(float64(size))
}

func (m *writeCacheMetrics) SetMode(shardID string, mode string) {
	m.modeMtx.Lock()
	defer m.modeMtx.Unlock()

	m.modeValues[shardID] = mode
	key := shardIDMode{
		shardID: shardID,
		mode:    mode,
	}
	if _, found := m.modeMetrics[key]; found {
		return
	}

	metric := newGaugeFunc(
		prometheus.GaugeOpts{
			Namespace: namespace,
			Subsystem: wcSubsystem,
			Name:      "writecache_mode",
			Help:      "Writecache mode value",
			ConstLabels: prometheus.Labels{
				wcShardID: shardID,
				wcMode:    mode,
			},
		}, func() float64 {
			m.modeMtx.RLock()
			defer m.modeMtx.RUnlock()

			value := m.modeValues[shardID]
			if value == mode {
				return 1
			}
			return 0
		})
	mustRegister(metric)
	m.modeMetrics[key] = metric
}

func (m *writeCacheMetrics) IncFlushCounter(shardID string, success bool, storageType string) {
	m.flushCounter.value.With(prometheus.Labels{
		wcShardID: shardID,
		wcSuccess: fmt.Sprintf("%v", success),
		wcStorage: storageType,
	}).Inc()
}

func (m *writeCacheMetrics) IncEvictCounter(shardID string, storageType string) {
	m.evictCounter.value.With(prometheus.Labels{
		wcShardID: shardID,
		wcStorage: storageType,
	}).Inc()
}

func (m *writeCacheMetrics) register() {
	mustRegister(m.getDuration)
	mustRegister(m.putDuration)
	mustRegister(m.deleteDuration)
	mustRegister(m.actualCount)
	mustRegister(m.estimatedSize)
	mustRegister(m.flushCounter)
	mustRegister(m.evictCounter)
}

func setWriteCacheDuration(m *prometheus.HistogramVec, shardID string, success bool, d time.Duration, storageType string) {
	m.With(
		prometheus.Labels{
			wcShardID: shardID,
			wcSuccess: fmt.Sprintf("%v", success),
			wcStorage: storageType,
		},
	).Observe(float64(d))
}

func newWCMethodDurationCounter(method string) metric[*prometheus.HistogramVec] {
	return newHistogramVec(prometheus.HistogramOpts{
		Namespace: namespace,
		Subsystem: wcSubsystem,
		Name:      fmt.Sprintf("%s_req_duration_seconds", method),
		Help:      fmt.Sprintf("Accumulated %s request process duration", method),
	}, []string{wcShardID, wcSuccess, wcStorage})
}

func newWCOperationCounterVec(operation string, labels []string) metric[*prometheus.CounterVec] {
	return newCounterVec(prometheus.CounterOpts{
		Namespace: namespace,
		Subsystem: wcSubsystem,
		Name:      fmt.Sprintf("%s_operation_count", operation),
		Help:      fmt.Sprintf("The number of %s operations processed", operation),
	}, labels)
}

func newWCGaugeVec(name, help string, labels []string) metric[*prometheus.GaugeVec] {
	return newGaugeVec(prometheus.GaugeOpts{
		Namespace: namespace,
		Subsystem: wcSubsystem,
		Name:      name,
		Help:      help,
	}, labels)
}