Clean up event switch add helper function

rpc/client/helpers.go

@@ -4,6 +4,8 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
+	cmn "github.com/tendermint/go-common"
+	events "github.com/tendermint/go-events"
 )
 
 // Waiter is informed of current height, decided whether to quit early
@@ -47,3 +49,36 @@ func WaitForHeight(c StatusClient, h int, waiter Waiter) error {
 	}
 	return nil
 }
+
+// WaitForOneEvent subscribes to a websocket event for the given
+// event time and returns upon receiving it one time, or
+// when the timeout duration has expired.
+//
+// This handles subscribing and unsubscribing under the hood
+func WaitForOneEvent(evsw events.EventSwitch,
+	evtTyp string, timeout time.Duration) (events.EventData, error) {
+	listener := cmn.RandStr(12)
+
+	evts, quit := make(chan events.EventData, 10), make(chan bool, 1)
+	// start timeout count-down
+	go func() {
+		time.Sleep(1 * time.Second)
+		quit <- true
+	}()
+
+	// register for the next event of this type
+	evsw.AddListenerForEvent(listener, evtTyp, func(data events.EventData) {
+		evts <- data
+	})
+	// make sure to unregister after the test is over
+	// TODO: don't require both!
+	defer evsw.RemoveListenerForEvent(listener, evtTyp)
+	defer evsw.RemoveListener(listener)
+
+	select {
+	case <-quit:
+		return nil, errors.New("timed out waiting for event")
+	case evt := <-evts:
+		return evt, nil
+	}
+}