// Package cache implements a simple LRU cache which can be completely purged
// whenever needed.
package cache

import (
	lru "github.com/hashicorp/golang-lru"
)

// Cache describes an in-memory cache for arbitrary objects, which has a Purge
// method for clearing everything at once.
type Cache interface {
	Get(key string) interface{}
	Set(key string, value interface{})
	Purge()
}

type cache struct {
	cache *lru.Cache
}

// New instantiates and returns a new Cache which can hold up to the given
// number of entries.
func New(size int) Cache {
	c, err := lru.New(size)

	// instantiating the lru cache can't realistically fail
	if err != nil {
		panic(err)
	}

	return &cache{c}
}

func (c *cache) Get(key string) interface{} {
	value, ok := c.cache.Get(key)
	if !ok {
		return nil
	}

	return value
}

func (c *cache) Set(key string, value interface{}) {
	c.cache.Add(key, value)
}

func (c *cache) Purge() {
	c.cache.Purge()
}