ezcache/ezcache.go

package ezcache

import (
	"sync"
	"time"
)

type ezc[K comparable, V any] struct {
	fetch    Fetcher[K, V]
	exp      time.Duration
	cache    map[K]V
	setTime  map[K]time.Time
	lock     sync.RWMutex
	timeLock sync.RWMutex
}

func New[K comparable, V any](fetcher Fetcher[K, V], exp time.Duration) (Cache[K, V], error) {
	c := &ezc[K, V]{}
	err := c.SetFetcher(fetcher)
	if err != nil {
		return nil, err
	}
	err = c.SetExpiry(exp)
	if err != nil {
		return nil, err
	}

	c.cache = make(map[K]V)
	c.setTime = make(map[K]time.Time)
	return c, nil
}

func (c *ezc[K, V]) Get(key K) (V, error) {
	c.timeLock.RLock()
	setTime, ok := c.setTime[key]
	c.timeLock.RUnlock()
	if ok && time.Since(setTime) <= c.exp {
		c.lock.RLock()
		val, ok := c.cache[key]
		c.lock.RUnlock()
		if ok {
			return val, nil
		}
	}

	val, err := c.fetch(key)
	if err != nil {
		return val, err
	}

	c.lock.Lock()
	defer c.lock.Unlock()
	c.cache[key] = val

	c.timeLock.Lock()
	defer c.timeLock.Unlock()
	c.setTime[key] = time.Now()

	return val, nil
}

func (c *ezc[K, V]) SetFetcher(f Fetcher[K, V]) error {
	if f == nil {
		return ErrInvalidFetcher
	}
	c.fetch = f
	return nil
}

func (c *ezc[K, V]) SetExpiry(exp time.Duration) error {
	if exp <= 0 {
		return ErrInvalidExpiry
	}
	c.exp = exp
	return nil
}