func (set TargetIDSet) Difference(sset TargetIDSet) TargetIDSet {
	nset := NewTargetIDSet()
	for k := range set {
		if _, ok := sset[k]; !ok {
			nset.add(k)
		}
	}

	return nset
}

// NewTargetIDSet - creates new TargetID set with given TargetIDs.
func NewTargetIDSet(targetIDs ...TargetID) TargetIDSet {
	set := make(TargetIDSet)
	for _, targetID := range targetIDs {

func (set TargetIDSet) Difference(sset TargetIDSet) TargetIDSet {
	nset := NewTargetIDSet()
	for k := range set {
		if _, ok := sset[k]; !ok {
			nset.add(k)
		}
	}

	return nset
}

// NewTargetIDSet - creates new TargetID set with given TargetIDs.
func NewTargetIDSet(targetIDs ...TargetID) TargetIDSet {
	set := make(TargetIDSet)
	for _, targetID := range targetIDs {

		expectedResult TargetIDSet
	}{
		{rulesMapCase1, ObjectCreatedPut, "2010/photo.jpg", NewTargetIDSet()},
		{rulesMapCase2, ObjectCreatedPut, "2010/photo.jpg", NewTargetIDSet(TargetID{"1", "webhook"})},
		{rulesMapCase3, ObjectCreatedPut, "2000/photo.png", NewTargetIDSet()},
		{rulesMapCase4, ObjectCreatedPut, "2000/photo.png", NewTargetIDSet(TargetID{"2", "amqp"})},
	}

	for i, testCase := range testCases {

	return pattern
}

// Rules - event rules
type Rules map[string]TargetIDSet

// Add - adds pattern and target ID.
func (rules Rules) Add(pattern string, targetID TargetID) {
	rules[pattern] = NewTargetIDSet(targetID).Union(rules[pattern])
}

// MatchSimple - returns true one of the matching object name in rules.
func (rules Rules) MatchSimple(objectName string) bool {
	for pattern := range rules {

}

// RemoveAllBucketTargets - closes and removes all notification targets.
func (evnot *EventNotifier) RemoveAllBucketTargets() {
	evnot.Lock()
	defer evnot.Unlock()

	targetIDSet := event.NewTargetIDSet()
	for k := range evnot.targetList.TargetMap() {
		targetIDSet[k] = struct{}{}
	}
	evnot.targetList.Remove(targetIDSet)
}

// Send - sends the event to all registered notification targets