package utils

import (
	"sync"
	"time"

	"github.com/patrickmn/go-cache"
)

// Cacher is a read-only cache interface.
//
// Get returns the value associated with the given key.
type Cacher interface {
	Get(string) (interface{}, error)
}

type defaultCache struct {
	cache  *cache.Cache
	lookup func(string) (interface{}, error)
	mutex  *sync.Mutex
}

func (c *defaultCache) Get(key string) (interface{}, error) {
	c.mutex.Lock()
	defer c.mutex.Unlock()

	if value, found := c.cache.Get(key); found {
		return value, nil
	}

	value, err := c.lookup(key)
	if err != nil {
		return nil, err
	}

	c.cache.SetDefault(key, value)
	return value, nil
}

// defaultCache implements the Cacher interface
var _ Cacher = (*defaultCache)(nil)

// NewDefaultCache returns cache with a 5 minute expiration.
func NewDefaultCache(lookup func(string) (interface{}, error)) (Cacher, error) {
	return &defaultCache{
		cache:  cache.New(5*time.Minute, 10*time.Minute),
		lookup: lookup,
		mutex:  &sync.Mutex{},
	}, nil
}