sdk/eventsdk: add GetStream() API

it broadcasts all events on every state change.

sdk/event/event.go

@@ -8,6 +8,9 @@ import (
 )
 
 const (
+	// StreamTopic is topic used to broadcast events.
+	StreamTopic = "event-stream"
+
 	topic = "Event"
 )
 
@@ -36,10 +39,18 @@ func (e *Event) Emit(token, eventKey string, eventData map[string]interface{}) e
 		return err
 	}
 
+	go e.ps.Pub(ev, StreamTopic)
 	go e.ps.Pub(ev, subTopic(s.Hash))
 	return nil
 }
 
+// GetStream broadcasts all events on every state change.
+func (e *Event) GetStream(f *Filter) *Listener {
+	l := NewListener(e.ps, StreamTopic, f)
+	go l.Listen()
+	return l
+}
+
 // Listen listens events matches with eventFilter on serviceID.
 func (e *Event) Listen(service string, f *Filter) (*Listener, error) {
 	s, err := e.db.Get(service)