addressing review comments

Signed-off-by: Soule BA <[email protected]>

cache/cache.go

@@ -240,7 +240,7 @@ func (c *cache[T]) get(key string) (T, bool, error) {
 		recordRequest(c.metrics, StatusSuccess)
 		return res, false, nil
 	}
-	if item.expiresAt.UnixNano() > 0 {
+	if !item.expiresAt.IsZero() {
 		if item.expiresAt.Compare(time.Now()) < 0 {
 			c.mu.RUnlock()
 			recordRequest(c.metrics, StatusSuccess)
@@ -430,7 +430,7 @@ func (c *Cache[T]) GetExpiration(object T) (time.Time, error) {
 		recordRequest(c.metrics, StatusSuccess)
 		return time.Time{}, KeyError{object, ErrNotFound}
 	}
-	if item.expiresAt.UnixNano() > 0 {
+	if !item.expiresAt.IsZero() {
 		if item.expiresAt.Compare(time.Now()) < 0 {
 			c.mu.RUnlock()
 			recordRequest(c.metrics, StatusSuccess)
@@ -459,10 +459,10 @@ func (c *cache[T]) deleteExpired() {
 		c.sorted = true
 	}
 
-	t := time.Now().UnixNano()
+	t := time.Now()
 	index := sort.Search(len(c.items), func(i int) bool {
 		// smallest index with an expiration greater than t
-		return c.items[i].expiresAt.UnixNano() > t
+		return c.items[i].expiresAt.Compare(t) > 0
 	})
 
 	// delete the expired indexes

cache/lru.go

@@ -42,6 +42,26 @@ func (n *node[T]) addPrev(node *node[T]) {
 // All methods are safe for concurrent use.
 // All operations are O(1). The hash map lookup is O(1) and so is the doubly
 // linked list insertion/deletion.
+//
+// The LRU is implemented as a doubly linked list, where the most recently accessed
+// item is at the front of the list and the least recently accessed item is at
+// the back. When an item is accessed, it is moved to the front of the list.
+// When the cache is full, the least recently accessed item is removed from the
+// back of the list.
+//
+//	Cache                                      
+//	┌───────────────────────────────────────────────────┐             
+//	│                                                   │             
+//	empty    │     obj         obj          obj          obj     │    empty    
+//	┌───────┐  │  ┌───────┐   ┌───────┐     ┌───────┐   ┌───────┐  │  ┌───────┐  
+//	│       │  │  │       │   │       │ ... │       │   │       │  │  │       │  
+//	│ HEAD  │◄─┼─►│       │◄─►│       │◄───►│       │◄─►│       │◄─┼─►│ TAIL  │  
+//	│       │  │  │       │   │       │     │       │   │       │  │  │       │  
+//	└───────┘  │  └───────┘   └───────┘     └───────┘   └───────┘  │  └───────┘  
+//	│                                                   │             
+//	│                                                   │             
+//	└───────────────────────────────────────────────────┘  
+//
 // A function to extract the key from the object must be provided.
 // Use the NewLRU function to create a new cache that is ready to use.
 type LRU[T any] struct {
@@ -165,6 +185,7 @@ func (c *LRU[T]) Delete(object T) error {
 
 func (c *LRU[T]) delete(node *node[T]) {
 	node.prev.next, node.next.prev = node.next, node.prev
+	node.next, node.prev = nil, nil // avoid memory leaks
 	delete(c.cache, node.key)
 }