Split sending into chained goroutines

main.go

@@ -97,7 +97,8 @@ func main() {
 	logger.Print("Created Telegram Bot API client")
 
 	tgSender := TgSender{bot}
-	go tgSenderWorker(tgEvents, tgSender, &wg, sleeper, log.New(os.Stderr, "TgSender", log.Lmicroseconds))
+	Consume(SendToTg(tgSenderWorker(tgEvents, &wg, sleeper, log.New(os.Stderr, "TgSender", log.Lmicroseconds)),
+		tgSender, &wg, log.New(os.Stderr, "SendToTg", log.Lmicroseconds)))
 	for e := range FilterByLastSeen(s.Events, "hs_wro_last_seen.bin", log.New(os.Stderr, "FilterByLastSeen", log.Lmicroseconds)) {
 		logger.Print("Received change from SATEL: ", e)
 		sendTgMessage(tgEvents, fmt.Sprint("Change from SATEL: type:", e.Type, ", index:", e.Index, ", value:", e.Value), chatIds)

sender_worker.go

@@ -19,54 +19,79 @@ type Sleeper interface {
 	Sleep(ch chan<- interface{})
 }
 
-func tgSenderWorker(tgEvents <-chan GenericMessage, s Sender, wg *sync.WaitGroup, sleeper Sleeper, logger *log.Logger) {
+func Consume(events <-chan GenericMessage) {
+	go func() {
+		for range events {
+		}
+	}()
+}
+
+func SendToTg(events <-chan GenericMessage, s Sender, wg *sync.WaitGroup, logger *log.Logger) <-chan GenericMessage {
+	returnEvents := make(chan GenericMessage)
+
+	go func() {
+		wg.Add(1)
+		defer wg.Done()
+		for e := range events {
+			returnEvents <- e
+			err := s.Send(e)
+			if err != nil {
+				// TODO: handle it better
+				panic(err)
+			}
+		}
+		close(returnEvents)
+	}()
+
+	return returnEvents
+}
+
+func tgSenderWorker(tgEvents <-chan GenericMessage, wg *sync.WaitGroup, sleeper Sleeper, logger *log.Logger) <-chan GenericMessage {
 	logger.Print("Starting")
-	wg.Add(1)
-	defer wg.Done()
 	messagesToSend := make(map[int64]*strings.Builder)
 	waitingStarted := false
 	timeoutEvents := make(chan interface{})
+	returnEvents := make(chan GenericMessage)
 
-loop:
-	for {
-		select {
-		case ev, ok := <-tgEvents:
-			if !ok {
-				break loop
-			}
-			// Collect all messages to send them at once
-			_, messageBuilderExists := messagesToSend[ev.chatId]
-			if !messageBuilderExists {
-				messagesToSend[ev.chatId] = &strings.Builder{}
-			}
-			messagesToSend[ev.chatId].WriteString(ev.msg)
-			messagesToSend[ev.chatId].WriteRune('\n')
-			if !waitingStarted {
-				logger.Print("Waiting for more messages to arrive before sending...")
-				waitingStarted = true
-				sleeper.Sleep(timeoutEvents)
-			}
-		case <-timeoutEvents:
-			logger.Print("Time's up, sending all messages we've got for now.")
-			waitingStarted = false
-			for chatId, msgBuilder := range messagesToSend {
-				err := s.Send(GenericMessage{chatId, msgBuilder.String()})
-				if err != nil {
-					// TODO: handle it better
-					panic(err)
+	go func() {
+		wg.Add(1)
+		defer wg.Done()
+		defer close(returnEvents)
+	loop:
+		for {
+			select {
+			case ev, ok := <-tgEvents:
+				if !ok {
+					break loop
+				}
+				// Collect all messages to send them at once
+				_, messageBuilderExists := messagesToSend[ev.chatId]
+				if !messageBuilderExists {
+					messagesToSend[ev.chatId] = &strings.Builder{}
+				}
+				messagesToSend[ev.chatId].WriteString(ev.msg)
+				messagesToSend[ev.chatId].WriteRune('\n')
+				if !waitingStarted {
+					logger.Print("Waiting for more messages to arrive before sending...")
+					waitingStarted = true
+					sleeper.Sleep(timeoutEvents)
+				}
+			case <-timeoutEvents:
+				logger.Print("Time's up, sending all messages we've got for now.")
+				waitingStarted = false
+				for chatId, msgBuilder := range messagesToSend {
+					returnEvents <- GenericMessage{chatId, msgBuilder.String()}
+					delete(messagesToSend, chatId)
 				}
-				delete(messagesToSend, chatId)
 			}
 		}
-	}
 
-	logger.Print("Exiting")
-	// If anything is left to be sent, send it now
-	for chatId, msgBuilder := range messagesToSend {
-		err := s.Send(GenericMessage{chatId, msgBuilder.String()})
-		if err != nil {
-			// TODO: handle it better
-			panic(err)
+		logger.Print("Exiting")
+		// If anything is left to be sent, send it now
+		for chatId, msgBuilder := range messagesToSend {
+			returnEvents <- GenericMessage{chatId, msgBuilder.String()}
 		}
-	}
+	}()
+
+	return returnEvents
 }

sender_worker_test.go

@@ -35,7 +35,8 @@ func TestMessageThrottling(t *testing.T) {
 	wg := sync.WaitGroup{}
 	mockSender := MockSender{make([]GenericMessage, 0)}
 	mockSleeper := MockSleeper{nil, 0}
-	go tgSenderWorker(testEvents, &mockSender, &wg, &mockSleeper, log.New(io.Discard, "", log.Ltime))
+	Consume(SendToTg(tgSenderWorker(testEvents, &wg, &mockSleeper, log.New(io.Discard, "", log.Ltime)),
+		&mockSender, &wg, log.New(io.Discard, "", log.Ltime)))
 	testEvents <- GenericMessage{123, "test1"}
 	testEvents <- GenericMessage{124, "test3"}
 	testEvents <- GenericMessage{123, "test2"}