make notification as separate package (#5294)

* Remove old notification files

* Add net package

* Add event package

* Modify minio to take new notification system

pkg/event/targetidset.go

@@ -0,0 +1,82 @@
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package event
+
+import "fmt"
+
+// TargetIDSet - Set representation of TargetIDs.
+type TargetIDSet map[TargetID]struct{}
+
+// ToSlice - returns TargetID slice from TargetIDSet.
+func (set TargetIDSet) ToSlice() []TargetID {
+	keys := make([]TargetID, 0, len(set))
+	for k := range set {
+		keys = append(keys, k)
+	}
+	return keys
+}
+
+// String - returns string representation.
+func (set TargetIDSet) String() string {
+	return fmt.Sprintf("%v", set.ToSlice())
+}
+
+// Clone - returns copy of this set.
+func (set TargetIDSet) Clone() TargetIDSet {
+	setCopy := NewTargetIDSet()
+	for k, v := range set {
+		setCopy[k] = v
+	}
+	return setCopy
+}
+
+// add - adds TargetID to the set.
+func (set TargetIDSet) add(targetID TargetID) {
+	set[targetID] = struct{}{}
+}
+
+// Union - returns union with given set as new set.
+func (set TargetIDSet) Union(sset TargetIDSet) TargetIDSet {
+	nset := set.Clone()
+
+	for k := range sset {
+		nset.add(k)
+	}
+
+	return nset
+}
+
+// Difference - returns diffrence with given set as new set.
+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 {
+		set.add(targetID)
+	}
+	return set
+}