Attachment behavior fix for Firefox

util/limit.go

@@ -15,6 +15,10 @@ var ErrLimitReached = errors.New("limit reached")
 type Limiter interface {
 	// Allow adds n to the limiters internal value, or returns ErrLimitReached if the limit has been reached
 	Allow(n int64) error
+
+	// Remaining returns the remaining count until the limit is reached; may return -1 if the implementation
+	// does not support this operation.
+	Remaining() int64
 }
 
 // FixedLimiter is a helper that allows adding values up to a well-defined limit. Once the limit is reached
@@ -44,6 +48,13 @@ func (l *FixedLimiter) Allow(n int64) error {
 	return nil
 }
 
+// Remaining  returns the remaining count until the limit is reached
+func (l *FixedLimiter) Remaining() int64 {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	return l.limit - l.value
+}
+
 // RateLimiter is a Limiter that wraps a rate.Limiter, allowing a floating time-based limit.
 type RateLimiter struct {
 	limiter *rate.Limiter
@@ -74,6 +85,11 @@ func (l *RateLimiter) Allow(n int64) error {
 	return nil
 }
 
+// Remaining is not implemented for RateLimiter. It always returns -1.
+func (l *RateLimiter) Remaining() int64 {
+	return -1
+}
+
 // LimitWriter implements an io.Writer that will pass through all Write calls to the underlying
 // writer w until any of the limiter's limit is reached, at which point a Write will return ErrLimitReached.
 // Each limiter's value is increased with every write.