LocalCache: Implement non-expiring cache with negative TTL (#56)

* LocalCache: Implement non-expiring cache with negative TTL

* Change NewCacheItem to support negative expiresAt

* Set neverExpires as const

* tests

Author: lucaslopezf

pkg/zcache/local_cache.go

@@ -11,19 +11,31 @@ import (
 	"time"
 )
 
+const (
+	neverExpires = -1
+)
+
 type CacheItem struct {
 	Value     []byte `json:"value"`
 	ExpiresAt int64  `json:"expires_at"`
 }
 
 func NewCacheItem(value []byte, ttl time.Duration) CacheItem {
+	expiresAt := time.Now().Add(ttl).Unix()
+	if ttl < 0 {
+		expiresAt = neverExpires
+	}
+
 	return CacheItem{
 		Value:     value,
-		ExpiresAt: time.Now().Add(ttl).Unix(),
+		ExpiresAt: expiresAt,
 	}
 }
 
 func (item CacheItem) IsExpired() bool {
+	if item.ExpiresAt < 0 {
+		return false
+	}
 	return time.Now().Unix() > item.ExpiresAt
 }
 

pkg/zcache/local_cache_test.go

@@ -5,6 +5,7 @@ import (
 	"github.com/stretchr/testify/suite"
 	"os"
 	"testing"
+	"time"
 )
 
 func TestLocalCacheTestSuite(t *testing.T) {
@@ -53,3 +54,19 @@ func (suite *LocalCacheTestSuite) TestDelete() {
 	err = suite.cache.Get(ctx, key, new(string))
 	suite.Error(err)
 }
+
+func (suite *LocalCacheTestSuite) TestCacheItemExpiration() {
+	item := NewCacheItem([]byte("testValue"), 1*time.Second)
+	suite.False(item.IsExpired(), "CacheItem should not be expired right after creation")
+	time.Sleep(2 * time.Second)
+
+	suite.True(item.IsExpired(), "CacheItem should be expired after its TTL")
+}
+
+func (suite *LocalCacheTestSuite) TestCacheItemNeverExpires() {
+	item := NewCacheItem([]byte("testValue"), -1)
+	suite.False(item.IsExpired(), "CacheItem with negative TTL should never expire")
+	time.Sleep(2 * time.Second)
+
+	suite.False(item.IsExpired(), "CacheItem with negative TTL should never expire, even after some time")
+}