Fix memory leak* when new message is received

*) technically the memory could still be referenced, so some would argue
   that it was not a memory leak, but when I see a program balooning up
   without a reason for it so OOM Killer deals with it I call it a
   memory leak, sue me

filters.go

@@ -89,7 +89,7 @@ func FilterByLastSeen(ev <-chan satel.Event, wg *sync.WaitGroup, dataStore *Data
 
 func appendToGenericMessage(msg *GenericMessage, new *GenericMessage) *GenericMessage {
 	if msg == nil {
-		return new
+		msg = &GenericMessage{new.ChatIds, make([]satel.BasicEventElement, 0)}
 	}
 
 throughNewMessages:
@@ -100,9 +100,9 @@ throughNewMessages:
 				msg.Messages[i].Value = newEv.Value
 				continue throughNewMessages
 			}
-			// apparently this type of message was not yet seen, save it
-			msg.Messages = append(msg.Messages, newEv)
 		}
+		// apparently this type of message was not yet seen, save it
+		msg.Messages = append(msg.Messages, newEv)
 	}
 	return msg
 }

filters_test.go

@@ -270,3 +270,55 @@ func TestThrottle(t *testing.T) {
 	assert.Contains(t, receivedEvents[1].Messages, tplMessageTest4)
 	assert.Len(t, receivedEvents[1].Messages, 1)
 }
+
+func makeMassiveEvent(element satel.BasicEventElement, numElements int) GenericMessage {
+	retval := GenericMessage{TgChatId{123}, make([]satel.BasicEventElement, 0)}
+
+	for i := 0; i < numElements; i++ {
+		retval.Messages = append(retval.Messages, element)
+	}
+
+	return retval
+}
+
+func TestThrottle_ManyMessagesInOneEvent(t *testing.T) {
+	testEvents := make(chan GenericMessage)
+	receivedEvents := make([]GenericMessage, 0)
+	wg := sync.WaitGroup{}
+	fakeLog := log.New(io.Discard, "", log.Ltime)
+	mockSleeper := MockSleeper{nil, 0}
+
+	var (
+		tplMessageTest1 = satel.BasicEventElement{Type: satel.ArmedPartition, Index: 1, Value: true}
+		tplMessageTest2 = satel.BasicEventElement{Type: satel.ZoneViolation, Index: 2, Value: true}
+		tplMessageTest3 = satel.BasicEventElement{Type: satel.ArmedPartition, Index: 1, Value: false}
+		tplMessageTest4 = satel.BasicEventElement{Type: satel.ZoneViolation, Index: 2, Value: false}
+	)
+
+	go func() {
+		wg.Add(1)
+		for e := range Throttle(testEvents, &wg, &mockSleeper, fakeLog) {
+			receivedEvents = append(receivedEvents, e)
+		}
+		wg.Done()
+	}()
+
+	testEvents <- makeMassiveEvent(tplMessageTest1, 100)
+	testEvents <- makeMassiveEvent(tplMessageTest2, 100)
+	testEvents <- makeMassiveEvent(tplMessageTest3, 100)
+	*mockSleeper.ch <- nil
+
+	testEvents <- makeMassiveEvent(tplMessageTest4, 100)
+
+	close(testEvents)
+	wg.Wait()
+
+	assert.Equal(t, 2, mockSleeper.callCount)
+	assert.Len(t, receivedEvents, 2)
+	assert.Contains(t, receivedEvents[0].Messages, tplMessageTest2)
+	assert.Contains(t, receivedEvents[0].Messages, tplMessageTest3)
+	assert.Len(t, receivedEvents[0].Messages, 2)
+
+	assert.Contains(t, receivedEvents[1].Messages, tplMessageTest4)
+	assert.Len(t, receivedEvents[1].Messages, 1)
+}