Merge pull request #19 from fastbill/add-cache-ttl

Add cache TTL method

cache/cache.go

@@ -27,6 +27,7 @@ type Cache interface {
 	GetJSON(key string, result interface{}) error
 	Del(key string) error
 	Close() error
+	TTL(key string) (time.Duration, error)
 }
 
 // RedisClient wraps the REDIS client to provide an implementation of the Cache interface.
@@ -156,6 +157,21 @@ func (r *RedisClient) Close() error {
 	return r.Redis.Close()
 }
 
+// TTL returns remaining time to live of the given key found in REDIS.
+// If the key doesn't exist, it returns ErrNotFound.
+func (r *RedisClient) TTL(key string) (time.Duration, error) {
+	result, err := r.Redis.TTL(key).Result()
+	if err != nil {
+		return 0, err
+	}
+
+	if result == -2 {
+		return 0, ErrNotFound
+	}
+
+	return result, nil
+}
+
 // prefixedKey adds the prefix in front of the key separated with ":".
 // If no prefix was provided for the client than the key is returned as is.
 func (r *RedisClient) prefixedKey(key string) string {

cache/cache_test.go

@@ -253,6 +253,40 @@ func TestDel(t *testing.T) {
 	})
 }
 
+func TestTTL(t *testing.T) {
+	t.Run("success", func(t *testing.T) {
+		withRedis(t, func(redis *miniredis.Miniredis, client *RedisClient) {
+			err := redis.Set("testPrefix:someKey", "100")
+			require.NoError(t, err)
+			redis.SetTTL("testPrefix:someKey", 1*time.Second)
+
+			result, err := client.TTL("testPrefix:someKey")
+
+			require.NoError(t, err)
+			assert.Equal(t, 1*time.Second, result)
+		})
+	})
+
+	t.Run("not found", func(t *testing.T) {
+		withRedis(t, func(redis *miniredis.Miniredis, client *RedisClient) {
+			_, err := client.TTL("testPrefix:someKey")
+
+			require.Error(t, err)
+			assert.Equal(t, ErrNotFound, err)
+		})
+	})
+
+	t.Run("failure", func(t *testing.T) {
+		withRedis(t, func(redis *miniredis.Miniredis, client *RedisClient) {
+			redis.Close()
+			_, err := client.TTL("testPrefix:someKey")
+
+			require.Error(t, err)
+			assert.NotEqual(t, ErrNotFound, err)
+		})
+	})
+}
+
 func withRedis(t *testing.T, fn func(redis *miniredis.Miniredis, client *RedisClient)) {
 	redis, err := miniredis.Run()
 	assert.NoError(t, err, "error in test setup")

cache/cachemock/cache.go

@@ -88,6 +88,17 @@ func (m *Cache) SetInt(key string, value int64, expiration time.Duration) error
 	return args.Error(0)
 }
 
+// TTL is a mock implementation of cache.Cache#TTL.
+func (m *Cache) TTL(key string) (time.Duration, error) {
+	args := m.Called(key)
+
+	if args.Get(0) != nil {
+		return args.Get(0).(time.Duration), args.Error(1)
+	}
+
+	return 0, args.Error(1)
+}
+
 // SetJSON is a mock implementation of cache.Cache#SetJSON.
 func (m *Cache) SetJSON(key string, value interface{}, expiration time.Duration) error {
 	args := m.Called(key, value, expiration)