fix cache incrementing (#388)

pkg/cache/cache.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -235,30 +236,78 @@ func (c *cache) Increment(key string, value int64) (int64, error) {
 	c.Lock()
 	defer c.Unlock()
 
-	var val int64
+	var val interface{}
 	if _, err := c.Get(key, &val); err != nil && err != ErrNotFound {
 		return 0, err
 	}
-	val += value
-	if err := c.Set(key, val, time.Time{}); err != nil {
-		return val, err
+
+	var counter int64
+
+	switch val.(type) {
+	case string:
+		// try to convert to number
+		a, err := strconv.ParseInt(val.(string), 10, 64)
+		if err != nil {
+			return 0, err
 		}
-	return val, nil
+		counter = a
+	case int64:
+		counter = val.(int64)
+	case int32:
+		counter = int64(val.(int32))
+	case int:
+		counter = int64(val.(int))
+	case nil:
+		counter = 0
+	default:
+		return 0, errors.New("value is not an integer")
+	}
+
+	counter += value
+
+	if err := c.Set(key, fmt.Sprintf("%v",counter), time.Time{}); err != nil {
+		return counter, err
+	}
+	return counter, nil
 }
 
 func (c *cache) Decrement(key string, value int64) (int64, error) {
 	c.Lock()
 	defer c.Unlock()
 
-	var val int64
+	var val interface{}
 	if _, err := c.Get(key, &val); err != nil && err != ErrNotFound {
 		return 0, err
 	}
-	val -= value
-	if err := c.Set(key, val, time.Time{}); err != nil {
-		return val, err
+
+	var counter int64
+
+	switch val.(type) {
+	case string:
+		// try to convert to number
+		a, err := strconv.ParseInt(val.(string), 10, 64)
+		if err != nil {
+			return 0, err
 		}
-	return val, nil
+		counter = a
+	case int64:
+		counter = val.(int64)
+	case int32:
+		counter = int64(val.(int32))
+	case int:
+		counter = int64(val.(int))
+	case nil:
+		counter = 0
+	default:
+		return 0, errors.New("value is not an integer")
+	}
+
+	counter -= value
+
+	if err := c.Set(key, fmt.Sprintf("%v", counter), time.Time{}); err != nil {
+		return counter, err
+	}
+	return counter, nil
 }
 
 func (c *cache) ListKeys() ([]string, error) {