// Memory Provider for the oci cache
// this provider is based on an arc cache
// ARCCache is a thread-safe fixed size Adaptive Replacement Cache (ARC)
// ARC is an enhancement over the standard LRU cache in that tracks both frequency and recency of use

package memory

import (
	v1 "github.com/google/go-containerregistry/pkg/v1"
	lru "github.com/hashicorp/golang-lru"
)

// ArcCache encapsulates an arc cache to store oci artifacts.
type ArcCache struct {
	store *lru.ARCCache
}

// New returns a new instance of the memory provider.
func New(limit int) (*ArcCache, error) {
	cache, err := lru.NewARC(limit)
	if err != nil {
		return nil, err
	}
	return &ArcCache{cache}, nil
}

// Get fetches an object from the arc cache if it exists
func (m *ArcCache) Get(h v1.Hash) (any, bool) {
	return m.store.Get(h)
}

// Keys returns the set of cache keys in the backing store
func (m *ArcCache) Keys() []any {
	return m.store.Keys()
}

// Exists check if the artifact with the specified hash exists in the arc cache
func (m *ArcCache) Exists(h v1.Hash) bool {
	return m.store.Contains(h)
}

// Add inserts an artifact to the arc cache
func (m *ArcCache) Add(h v1.Hash, obj any) {
	m.store.Add(h, obj)
}

// Len returns number of entries in cache.
func (m *ArcCache) Len() int {
	return m.store.Len()
}

func (m *ArcCache) Purge() {
	m.store.Purge()
}