Add registry event to registry package

registry/watcher.go

@@ -1,5 +1,7 @@
 package registry
 
+import "time"
+
 // Watcher is an interface that returns updates
 // about services within the registry.
 type Watcher interface {
@@ -14,3 +16,41 @@ type Result struct {
 	Action  string
 	Service *Service
 }
+
+// EventType defines registry event type
+type EventType int
+
+const (
+	// Create is emitted when a new service is registered
+	Create EventType = iota
+	// Delete is emitted when an existing service is deregsitered
+	Delete
+	// Update is emitted when an existing servicec is updated
+	Update
+)
+
+// String returns human readable event type
+func (t EventType) String() string {
+	switch t {
+	case Create:
+		return "create"
+	case Delete:
+		return "delete"
+	case Update:
+		return "update"
+	default:
+		return "unknown"
+	}
+}
+
+// Event is registry event
+type Event struct {
+	// Id is registry id
+	Id string
+	// Type defines type of event
+	Type EventType
+	// Timestamp is event timestamp
+	Timestamp time.Time
+	// Service is registry service
+	Service *Service
+}