package cache

import (
	"sync"
	"sync/atomic"
	"time"
)

const (

	maximumCapacity = 1 << 30

	chanBufSize = 64

	drainMax = 16

	drainThreshold = 64
)

var currentTime = time.Now

type localCache struct {

	policyName        string
	expireAfterAccess time.Duration
	expireAfterWrite  time.Duration
	refreshAfterWrite time.Duration

	onInsertion Func
	onRemoval   Func

	loader LoaderFunc
	exec   Executor
	stats  StatsCounter

	cache cache
	cap   int

	accessQueue policy

	writeQueue policy

	events chan entryEvent

	readCount int32

	closing int32
	closeWG sync.WaitGroup
}

func newLocalCache() *localCache {
	return &localCache{
		cap:   maximumCapacity,
		cache: cache{},
		stats: &statsCounter{},
	}
}

func (c *localCache) init() {
	c.accessQueue = newPolicy(c.policyName)
	c.accessQueue.init(&c.cache, c.cap)
	if c.expireAfterWrite > 0 || c.refreshAfterWrite > 0 {
		c.writeQueue = &recencyQueue{}
	} else {
		c.writeQueue = discardingQueue{}
	}
	c.writeQueue.init(&c.cache, c.cap)
	c.events = make(chan entryEvent, chanBufSize)

	c.closeWG.Add(1)
	go c.processEntries()
}

func (c *localCache) Close() error {
	if atomic.CompareAndSwapInt32(&c.closing, 0, 1) {

		c.events <- entryEvent{nil, eventClose}

		c.closeWG.Wait()
	}
	return nil
}

func (c *localCache) GetIfPresent(k Key) (Value, bool) {
	en := c.cache.get(k, sum(k))
	if en == nil {
		c.stats.RecordMisses(1)
		return nil, false
	}
	now := currentTime()
	if c.isExpired(en, now) {
		c.stats.RecordMisses(1)
		c.sendEvent(eventDelete, en)
		return nil, false
	}
	c.stats.RecordHits(1)
	c.setEntryAccessTime(en, now)
	c.sendEvent(eventAccess, en)
	return en.getValue(), true
}

func (c *localCache) Put(k Key, v Value) {
	h := sum(k)
	en := c.cache.get(k, h)
	now := currentTime()
	if en == nil {
		en = newEntry(k, v, h)
		c.setEntryWriteTime(en, now)
		c.setEntryAccessTime(en, now)

		if c.cap == 0 || c.cache.len() < c.cap {
			cen := c.cache.getOrSet(en)
			if cen != nil {
				cen.setValue(v)
				en = cen
			}
		}
	} else {

		en.setValue(v)
		en.setWriteTime(now.UnixNano())
	}
	c.sendEvent(eventWrite, en)
}

func (c *localCache) Invalidate(k Key) {
	en := c.cache.get(k, sum(k))
	if en != nil {
		en.setInvalidated(true)
		c.sendEvent(eventDelete, en)
	}
}

func (c *localCache) InvalidateAll() {
	c.cache.walk(func(en *entry) {
		en.setInvalidated(true)
	})
	c.sendEvent(eventDelete, nil)
}

func (c *localCache) Get(k Key) (Value, error) {
	en := c.cache.get(k, sum(k))
	if en == nil {
		c.stats.RecordMisses(1)
		return c.load(k)
	}

	now := currentTime()
	if c.isExpired(en, now) {
		c.stats.RecordMisses(1)
		if c.loader == nil {
			c.sendEvent(eventDelete, en)
		} else {

			c.setEntryAccessTime(en, now)
			c.refreshAsync(en)
		}
	} else {
		c.stats.RecordHits(1)
		c.setEntryAccessTime(en, now)
		c.sendEvent(eventAccess, en)
	}
	return en.getValue(), nil
}

func (c *localCache) Refresh(k Key) {
	if c.loader == nil {
		return
	}
	en := c.cache.get(k, sum(k))
	if en == nil {
		c.load(k)
	} else {
		c.refreshAsync(en)
	}
}

func (c *localCache) Stats(t *Stats) {
	c.stats.Snapshot(t)
}

func (c *localCache) processEntries() {
	defer c.closeWG.Done()
	for e := range c.events {
		switch e.event {
		case eventWrite:
			c.write(e.entry)
			c.postWriteCleanup()
		case eventAccess:
			c.access(e.entry)
			c.postReadCleanup()
		case eventDelete:
			if e.entry == nil {
				c.removeAll()
			} else {
				c.remove(e.entry)
			}
			c.postReadCleanup()
		case eventClose:
			if c.exec != nil {

				c.exec.Close()
			}
			c.removeAll()
			return
		}
	}
}

func (c *localCache) sendEvent(typ event, en *entry) {
	if atomic.LoadInt32(&c.closing) == 0 {
		c.events <- entryEvent{en, typ}
	}
}

func (c *localCache) write(en *entry) {
	ren := c.accessQueue.write(en)
	c.writeQueue.write(en)
	if c.onInsertion != nil {
		c.onInsertion(en.key, en.getValue())
	}
	if ren != nil {
		c.writeQueue.remove(ren)

		c.stats.RecordEviction()
		if c.onRemoval != nil {
			c.onRemoval(ren.key, ren.getValue())
		}
	}
}

func (c *localCache) removeAll() {
	c.accessQueue.iterate(func(en *entry) bool {
		c.remove(en)
		return true
	})
}

func (c *localCache) remove(en *entry) {
	ren := c.accessQueue.remove(en)
	c.writeQueue.remove(en)
	if ren != nil {
		if c.onRemoval != nil {
			c.onRemoval(ren.key, ren.getValue())
		}
	}
}

func (c *localCache) access(en *entry) {
	c.accessQueue.access(en)
}

func (c *localCache) load(k Key) (Value, error) {
	if c.loader == nil {
		panic("cache loader function must be set")
	}

	start := currentTime()
	v, err := c.loader(k)
	now := currentTime()
	loadTime := now.Sub(start)
	if err != nil {
		c.stats.RecordLoadError(loadTime)
		return nil, err
	}
	c.stats.RecordLoadSuccess(loadTime)
	en := newEntry(k, v, sum(k))
	c.setEntryWriteTime(en, now)
	c.setEntryAccessTime(en, now)
	c.sendEvent(eventWrite, en)
	return v, nil
}

func (c *localCache) refreshAsync(en *entry) bool {
	if c.loader == nil {
		panic("cache loader function must be set")
	}
	if en.setLoading(true) {

		if c.exec == nil {
			go c.refresh(en)
		} else {
			c.exec.Execute(func() { c.refresh(en) })
		}
		return true
	}
	return false
}

func (c *localCache) refresh(en *entry) {
	defer en.setLoading(false)

	start := currentTime()
	v, err := c.loader(en.key)
	now := currentTime()
	loadTime := now.Sub(start)
	if err == nil {
		c.stats.RecordLoadSuccess(loadTime)
		en.setValue(v)
		en.setWriteTime(now.UnixNano())
		c.sendEvent(eventWrite, en)
	} else {

		c.stats.RecordLoadError(loadTime)
	}
}

func (c *localCache) postReadCleanup() {
	if atomic.AddInt32(&c.readCount, 1) > drainThreshold {
		atomic.StoreInt32(&c.readCount, 0)
		c.expireEntries()
	}
}

func (c *localCache) postWriteCleanup() {
	atomic.StoreInt32(&c.readCount, 0)
	c.expireEntries()
}

func (c *localCache) expireEntries() {
	remain := drainMax
	now := currentTime()
	if c.expireAfterAccess > 0 {
		expiry := now.Add(-c.expireAfterAccess).UnixNano()
		c.accessQueue.iterate(func(en *entry) bool {
			if remain == 0 || en.getAccessTime() >= expiry {

				return false
			}

			c.remove(en)
			c.stats.RecordEviction()
			remain--
			return remain > 0
		})
	}
	if remain > 0 && c.expireAfterWrite > 0 {
		expiry := now.Add(-c.expireAfterWrite).UnixNano()
		c.writeQueue.iterate(func(en *entry) bool {
			if remain == 0 || en.getWriteTime() >= expiry {
				return false
			}

			c.remove(en)
			c.stats.RecordEviction()
			remain--
			return remain > 0
		})
	}
	if remain > 0 && c.loader != nil && c.refreshAfterWrite > 0 {
		expiry := now.Add(-c.refreshAfterWrite).UnixNano()
		c.writeQueue.iterate(func(en *entry) bool {
			if remain == 0 || en.getWriteTime() >= expiry {
				return false
			}

			if c.refreshAsync(en) {

				remain--
			}
			return remain > 0
		})
	}
}

func (c *localCache) isExpired(en *entry, now time.Time) bool {
	if en.getInvalidated() {
		return true
	}
	if c.expireAfterAccess > 0 && en.getAccessTime() < now.Add(-c.expireAfterAccess).UnixNano() {

		return true
	}
	if c.expireAfterWrite > 0 && en.getWriteTime() < now.Add(-c.expireAfterWrite).UnixNano() {

		return true
	}
	return false
}

func (c *localCache) needRefresh(en *entry, now time.Time) bool {
	if en.getLoading() {
		return false
	}
	if c.refreshAfterWrite > 0 {
		tm := en.getWriteTime()
		if tm > 0 && tm < now.Add(-c.refreshAfterWrite).UnixNano() {

			return true
		}
	}
	return false
}

func (c *localCache) setEntryAccessTime(en *entry, now time.Time) {
	if c.expireAfterAccess > 0 {
		en.setAccessTime(now.UnixNano())
	}
}

func (c *localCache) setEntryWriteTime(en *entry, now time.Time) {
	if c.expireAfterWrite > 0 || c.refreshAfterWrite > 0 {
		en.setWriteTime(now.UnixNano())
	}
}

func New(options ...Option) Cache {
	c := newLocalCache()
	for _, opt := range options {
		opt(c)
	}
	c.init()
	return c
}

func NewLoadingCache(loader LoaderFunc, options ...Option) LoadingCache {
	c := newLocalCache()
	c.loader = loader
	for _, opt := range options {
		opt(c)
	}
	c.init()
	return c
}

type Option func(c *localCache)

func WithMaximumSize(size int) Option {
	if size < 0 {
		size = 0
	}
	if size > maximumCapacity {
		size = maximumCapacity
	}
	return func(c *localCache) {
		c.cap = size
	}
}

func WithRemovalListener(onRemoval Func) Option {
	return func(c *localCache) {
		c.onRemoval = onRemoval
	}
}

func WithExpireAfterAccess(d time.Duration) Option {
	return func(c *localCache) {
		c.expireAfterAccess = d
	}
}

func WithExpireAfterWrite(d time.Duration) Option {
	return func(c *localCache) {
		c.expireAfterWrite = d
	}
}

func WithRefreshAfterWrite(d time.Duration) Option {
	return func(c *localCache) {
		c.refreshAfterWrite = d
	}
}

func WithStatsCounter(st StatsCounter) Option {
	return func(c *localCache) {
		c.stats = st
	}
}

func WithPolicy(name string) Option {
	return func(c *localCache) {
		c.policyName = name
	}
}

func WithExecutor(executor Executor) Option {
	return func(c *localCache) {
		c.exec = executor
	}
}

func withInsertionListener(onInsertion Func) Option {
	return func(c *localCache) {
		c.onInsertion = onInsertion
	}
}
package cache

import (
	"sync"
	"sync/atomic"
	"time"
)

const (
	// Default maximum number of cache entries.
	maximumCapacity = 1 << 30
	// Buffer size of entry channels
	chanBufSize = 64
	// Maximum number of entries to be drained in a single clean up.
	drainMax = 16
	// Number of cache access operations that will trigger clean up.
	drainThreshold = 64
)

// currentTime is an alias for time.Now, used for testing.
var currentTime = time.Now

// localCache is an asynchronous LRU cache.
type localCache struct {
	// user configurations
	policyName        string
	expireAfterAccess time.Duration
	expireAfterWrite  time.Duration
	refreshAfterWrite time.Duration

	onInsertion Func
	onRemoval   Func

	loader LoaderFunc
	exec   Executor
	stats  StatsCounter

	// internal data structure
	cache cache
	cap   int

	// accessQueue is the cache retention policy, which manages entries by access time.
	accessQueue policy
	// writeQueue is for managing entries by write time.
	// It is only fulfilled when expireAfterWrite or refreshAfterWrite is set.
	writeQueue policy
	// events is the cache event queue for processEntries
	events chan entryEvent

	// readCount is a counter of the number of reads since the last write.
	readCount int32

	// for closing routines created by this cache.
	closing int32
	closeWG sync.WaitGroup
}

// newLocalCache returns a default localCache.
// init must be called before this cache can be used.
func newLocalCache() *localCache {
	return &localCache{
		cap:   maximumCapacity,
		cache: cache{},
		stats: &statsCounter{},
	}
}

// init initializes cache replacement policy after all user configuration properties are set.
func (c *localCache) init() {
	c.accessQueue = newPolicy(c.policyName)
	c.accessQueue.init(&c.cache, c.cap)
	if c.expireAfterWrite > 0 || c.refreshAfterWrite > 0 {
		c.writeQueue = &recencyQueue{}
	} else {
		c.writeQueue = discardingQueue{}
	}
	c.writeQueue.init(&c.cache, c.cap)
	c.events = make(chan entryEvent, chanBufSize)

	c.closeWG.Add(1)
	go c.processEntries()
}

// Close implements io.Closer and always returns a nil error.
// Caller would ensure the cache is not being used (reading and writing) before closing.
func (c *localCache) Close() error {
	if atomic.CompareAndSwapInt32(&c.closing, 0, 1) {
		// Do not close events channel to avoid panic when cache is still being used.
		c.events <- entryEvent{nil, eventClose}
		// Wait for the goroutine to close this channel
		c.closeWG.Wait()
	}
	return nil
}

// GetIfPresent gets cached value from entries list and updates
// last access time for the entry if it is found.
func (c *localCache) GetIfPresent(k Key) (Value, bool) {
	en := c.cache.get(k, sum(k))
	if en == nil {
		c.stats.RecordMisses(1)
		return nil, false
	}
	now := currentTime()
	if c.isExpired(en, now) {
		c.stats.RecordMisses(1)
		c.sendEvent(eventDelete, en)
		return nil, false
	}
	c.stats.RecordHits(1)
	c.setEntryAccessTime(en, now)
	c.sendEvent(eventAccess, en)
	return en.getValue(), true
}

// Put adds new entry to entries list.
func (c *localCache) Put(k Key, v Value) {
	h := sum(k)
	en := c.cache.get(k, h)
	now := currentTime()
	if en == nil {
		en = newEntry(k, v, h)
		c.setEntryWriteTime(en, now)
		c.setEntryAccessTime(en, now)
		// Add to the cache directly so the new value is available immediately.
		// However, only do this within the cache capacity (approximately).
		if c.cap == 0 || c.cache.len() < c.cap {
			cen := c.cache.getOrSet(en)
			if cen != nil {
				cen.setValue(v)
				en = cen
			}
		}
	} else {
		// Update value and send notice
		en.setValue(v)
		en.setWriteTime(now.UnixNano())
	}
	c.sendEvent(eventWrite, en)
}

// Invalidate removes the entry associated with key k.
func (c *localCache) Invalidate(k Key) {
	en := c.cache.get(k, sum(k))
	if en != nil {
		en.setInvalidated(true)
		c.sendEvent(eventDelete, en)
	}
}

// InvalidateAll resets entries list.
func (c *localCache) InvalidateAll() {
	c.cache.walk(func(en *entry) {
		en.setInvalidated(true)
	})
	c.sendEvent(eventDelete, nil)
}

// Get returns value associated with k or call underlying loader to retrieve value
// if it is not in the cache. The returned value is only cached when loader returns
// nil error.
func (c *localCache) Get(k Key) (Value, error) {
	en := c.cache.get(k, sum(k))
	if en == nil {
		c.stats.RecordMisses(1)
		return c.load(k)
	}
	// Check if this entry needs to be refreshed
	now := currentTime()
	if c.isExpired(en, now) {
		c.stats.RecordMisses(1)
		if c.loader == nil {
			c.sendEvent(eventDelete, en)
		} else {
			// For loading cache, we do not delete entry but leave it to
			// the eviction policy, so users still can get the old value.
			c.setEntryAccessTime(en, now)
			c.refreshAsync(en)
		}
	} else {
		c.stats.RecordHits(1)
		c.setEntryAccessTime(en, now)
		c.sendEvent(eventAccess, en)
	}
	return en.getValue(), nil
}

// Refresh asynchronously reloads value for Key if it existed, otherwise
// it will synchronously load and block until it value is loaded.
func (c *localCache) Refresh(k Key) {
	if c.loader == nil {
		return
	}
	en := c.cache.get(k, sum(k))
	if en == nil {
		c.load(k)
	} else {
		c.refreshAsync(en)
	}
}

// Stats copies cache stats to t.
func (c *localCache) Stats(t *Stats) {
	c.stats.Snapshot(t)
}

func (c *localCache) processEntries() {
	defer c.closeWG.Done()
	for e := range c.events {
		switch e.event {
		case eventWrite:
			c.write(e.entry)
			c.postWriteCleanup()
		case eventAccess:
			c.access(e.entry)
			c.postReadCleanup()
		case eventDelete:
			if e.entry == nil {
				c.removeAll()
			} else {
				c.remove(e.entry)
			}
			c.postReadCleanup()
		case eventClose:
			if c.exec != nil {
				// Stop all refresh tasks.
				c.exec.Close()
			}
			c.removeAll()
			return
		}
	}
}

// sendEvent sends event only when the cache is not closing/closed.
func (c *localCache) sendEvent(typ event, en *entry) {
	if atomic.LoadInt32(&c.closing) == 0 {
		c.events <- entryEvent{en, typ}
	}
}

// This function must only be called from processEntries goroutine.
func (c *localCache) write(en *entry) {
	ren := c.accessQueue.write(en)
	c.writeQueue.write(en)
	if c.onInsertion != nil {
		c.onInsertion(en.key, en.getValue())
	}
	if ren != nil {
		c.writeQueue.remove(ren)
		// An entry has been evicted
		c.stats.RecordEviction()
		if c.onRemoval != nil {
			c.onRemoval(ren.key, ren.getValue())
		}
	}
}

// removeAll remove all entries in the cache.
// This function must only be called from processEntries goroutine.
func (c *localCache) removeAll() {
	c.accessQueue.iterate(func(en *entry) bool {
		c.remove(en)
		return true
	})
}

// remove removes the given element from the cache and entries list.
// It also calls onRemoval callback if it is set.
func (c *localCache) remove(en *entry) {
	ren := c.accessQueue.remove(en)
	c.writeQueue.remove(en)
	if ren != nil {
		if c.onRemoval != nil {
			c.onRemoval(ren.key, ren.getValue())
		}
	}
}

// access moves the given element to the top of the entries list.
// This function must only be called from processEntries goroutine.
func (c *localCache) access(en *entry) {
	c.accessQueue.access(en)
}

// load uses current loader to synchronously retrieve value for k and adds new
// entry to the cache only if loader returns a nil error.
func (c *localCache) load(k Key) (Value, error) {
	if c.loader == nil {
		panic("cache loader function must be set")
	}
	// TODO: Poll the value instead when the entry is loading.
	start := currentTime()
	v, err := c.loader(k)
	now := currentTime()
	loadTime := now.Sub(start)
	if err != nil {
		c.stats.RecordLoadError(loadTime)
		return nil, err
	}
	c.stats.RecordLoadSuccess(loadTime)
	en := newEntry(k, v, sum(k))
	c.setEntryWriteTime(en, now)
	c.setEntryAccessTime(en, now)
	c.sendEvent(eventWrite, en)
	return v, nil
}

// refreshAsync reloads value in a go routine or using custom executor if defined.
func (c *localCache) refreshAsync(en *entry) bool {
	if c.loader == nil {
		panic("cache loader function must be set")
	}
	if en.setLoading(true) {
		// Only do refresh if it isn't running.
		if c.exec == nil {
			go c.refresh(en)
		} else {
			c.exec.Execute(func() { c.refresh(en) })
		}
		return true
	}
	return false
}

// refresh reloads value for the given key. If loader returns an error,
// that error will be omitted. Otherwise, the entry value will be updated.
// This function would only be called by refreshAsync.
func (c *localCache) refresh(en *entry) {
	defer en.setLoading(false)

	start := currentTime()
	v, err := c.loader(en.key)
	now := currentTime()
	loadTime := now.Sub(start)
	if err == nil {
		c.stats.RecordLoadSuccess(loadTime)
		en.setValue(v)
		en.setWriteTime(now.UnixNano())
		c.sendEvent(eventWrite, en)
	} else {
		// TODO: Log error
		c.stats.RecordLoadError(loadTime)
	}
}

// postReadCleanup is run after entry access/delete event.
// This function must only be called from processEntries goroutine.
func (c *localCache) postReadCleanup() {
	if atomic.AddInt32(&c.readCount, 1) > drainThreshold {
		atomic.StoreInt32(&c.readCount, 0)
		c.expireEntries()
	}
}

// postWriteCleanup is run after entry add event.
// This function must only be called from processEntries goroutine.
func (c *localCache) postWriteCleanup() {
	atomic.StoreInt32(&c.readCount, 0)
	c.expireEntries()
}

// expireEntries removes expired entries.
func (c *localCache) expireEntries() {
	remain := drainMax
	now := currentTime()
	if c.expireAfterAccess > 0 {
		expiry := now.Add(-c.expireAfterAccess).UnixNano()
		c.accessQueue.iterate(func(en *entry) bool {
			if remain == 0 || en.getAccessTime() >= expiry {
				// Can stop as the entries are sorted by access time.
				// (the next entry is accessed more recently.)
				return false
			}
			// accessTime + expiry passed
			c.remove(en)
			c.stats.RecordEviction()
			remain--
			return remain > 0
		})
	}
	if remain > 0 && c.expireAfterWrite > 0 {
		expiry := now.Add(-c.expireAfterWrite).UnixNano()
		c.writeQueue.iterate(func(en *entry) bool {
			if remain == 0 || en.getWriteTime() >= expiry {
				return false
			}
			// writeTime + expiry passed
			c.remove(en)
			c.stats.RecordEviction()
			remain--
			return remain > 0
		})
	}
	if remain > 0 && c.loader != nil && c.refreshAfterWrite > 0 {
		expiry := now.Add(-c.refreshAfterWrite).UnixNano()
		c.writeQueue.iterate(func(en *entry) bool {
			if remain == 0 || en.getWriteTime() >= expiry {
				return false
			}
			// FIXME: This can cause deadlock if the custom executor runs refresh in current go routine.
			// The refresh function, when finish, will send to event channels.
			if c.refreshAsync(en) {
				// TODO: Maybe move this entry up?
				remain--
			}
			return remain > 0
		})
	}
}

func (c *localCache) isExpired(en *entry, now time.Time) bool {
	if en.getInvalidated() {
		return true
	}
	if c.expireAfterAccess > 0 && en.getAccessTime() < now.Add(-c.expireAfterAccess).UnixNano() {
		// accessTime + expiry passed
		return true
	}
	if c.expireAfterWrite > 0 && en.getWriteTime() < now.Add(-c.expireAfterWrite).UnixNano() {
		// writeTime + expiry passed
		return true
	}
	return false
}

func (c *localCache) needRefresh(en *entry, now time.Time) bool {
	if en.getLoading() {
		return false
	}
	if c.refreshAfterWrite > 0 {
		tm := en.getWriteTime()
		if tm > 0 && tm < now.Add(-c.refreshAfterWrite).UnixNano() {
			// writeTime + refresh passed
			return true
		}
	}
	return false
}

// setEntryAccessTime sets access time if needed.
func (c *localCache) setEntryAccessTime(en *entry, now time.Time) {
	if c.expireAfterAccess > 0 {
		en.setAccessTime(now.UnixNano())
	}
}

// setEntryWriteTime sets write time if needed.
func (c *localCache) setEntryWriteTime(en *entry, now time.Time) {
	if c.expireAfterWrite > 0 || c.refreshAfterWrite > 0 {
		en.setWriteTime(now.UnixNano())
	}
}

// New returns a local in-memory Cache.
func New(options ...Option) Cache {
	c := newLocalCache()
	for _, opt := range options {
		opt(c)
	}
	c.init()
	return c
}

// NewLoadingCache returns a new LoadingCache with given loader function
// and cache options.
func NewLoadingCache(loader LoaderFunc, options ...Option) LoadingCache {
	c := newLocalCache()
	c.loader = loader
	for _, opt := range options {
		opt(c)
	}
	c.init()
	return c
}

// Option add options for default Cache.
type Option func(c *localCache)

// WithMaximumSize returns an Option which sets maximum size for the cache.
// Any non-positive numbers is considered as unlimited.
func WithMaximumSize(size int) Option {
	if size < 0 {
		size = 0
	}
	if size > maximumCapacity {
		size = maximumCapacity
	}
	return func(c *localCache) {
		c.cap = size
	}
}

// WithRemovalListener returns an Option to set cache to call onRemoval for each
// entry evicted from the cache.
func WithRemovalListener(onRemoval Func) Option {
	return func(c *localCache) {
		c.onRemoval = onRemoval
	}
}

// WithExpireAfterAccess returns an option to expire a cache entry after the
// given duration without being accessed.
func WithExpireAfterAccess(d time.Duration) Option {
	return func(c *localCache) {
		c.expireAfterAccess = d
	}
}

// WithExpireAfterWrite returns an option to expire a cache entry after the
// given duration from creation.
func WithExpireAfterWrite(d time.Duration) Option {
	return func(c *localCache) {
		c.expireAfterWrite = d
	}
}

// WithRefreshAfterWrite returns an option to refresh a cache entry after the
// given duration. This option is only applicable for LoadingCache.
func WithRefreshAfterWrite(d time.Duration) Option {
	return func(c *localCache) {
		c.refreshAfterWrite = d
	}
}

// WithStatsCounter returns an option which overrides default cache stats counter.
func WithStatsCounter(st StatsCounter) Option {
	return func(c *localCache) {
		c.stats = st
	}
}

// WithPolicy returns an option which sets cache policy associated to the given name.
// Supported policies are: lru, slru, tinylfu.
func WithPolicy(name string) Option {
	return func(c *localCache) {
		c.policyName = name
	}
}

// WithExecutor returns an option which sets executor for cache loader.
// By default, each asynchronous reload is run in a go routine.
// This option is only applicable for LoadingCache.
func WithExecutor(executor Executor) Option {
	return func(c *localCache) {
		c.exec = executor
	}
}

// withInsertionListener is used for testing.
func withInsertionListener(onInsertion Func) Option {
	return func(c *localCache) {
		c.onInsertion = onInsertion
	}
}
