feat: introduce `MessagesOrderController`

Enables controlling order of messages in tests. Useful for deterministic
reproduction of out-of-order messages.

Required for: status-im/status-desktop#13387

protocol/messenger_builder_test.go

@@ -25,6 +25,8 @@ type testMessengerConfig struct {
 	logger     *zap.Logger
 
 	unhandledMessagesTracker *unhandledMessagesTracker
+	messagesOrderController  *MessagesOrderController
+
 	extraOptions []Option
 }
 
@@ -99,6 +101,10 @@ func newTestMessenger(waku types.Waku, config testMessengerConfig) (*Messenger,
 		m.unhandledMessagesTracker = config.unhandledMessagesTracker.addMessage
 	}
 
+	if config.messagesOrderController != nil {
+		m.retrievedMessagesIteratorFactory = config.messagesOrderController.newMessagesIterator
+	}
+
 	err = m.Init()
 	if err != nil {
 		return nil, err

protocol/messenger_messages_order_controller_test.go

@@ -0,0 +1,130 @@
+package protocol
+
+import (
+	"sort"
+	"sync"
+
+	"github.com/status-im/status-go/eth-node/types"
+	"github.com/status-im/status-go/protocol/transport"
+)
+
+type messagesOrderType int
+
+const (
+	messagesOrderRandom messagesOrderType = iota
+	messagesOrderAsPosted
+	messagesOrderReversed
+)
+
+type MessagesOrderController struct {
+	order               messagesOrderType
+	messagesInPostOrder [][]byte
+	mutex               sync.RWMutex
+	quit                chan struct{}
+	quitOnce            sync.Once
+}
+
+func NewMessagesOrderController(order messagesOrderType) *MessagesOrderController {
+	return &MessagesOrderController{
+		order:               order,
+		messagesInPostOrder: [][]byte{},
+		mutex:               sync.RWMutex{},
+		quit:                make(chan struct{}),
+	}
+}
+
+func (m *MessagesOrderController) Start(c chan *PostMessageSubscription) {
+	go func() {
+		for {
+			select {
+			case sub, more := <-c:
+				if !more {
+					return
+				}
+				m.mutex.Lock()
+				m.messagesInPostOrder = append(m.messagesInPostOrder, sub.id)
+				m.mutex.Unlock()
+
+			case <-m.quit:
+				return
+			}
+		}
+	}()
+}
+
+func (m *MessagesOrderController) Stop() {
+	m.quitOnce.Do(func() {
+		close(m.quit)
+	})
+}
+
+func (m *MessagesOrderController) newMessagesIterator(chatWithMessages map[transport.Filter][]*types.Message) MessagesIterator {
+	switch m.order {
+	case messagesOrderAsPosted, messagesOrderReversed:
+		return &messagesIterator{chatWithMessages: m.sort(chatWithMessages, m.order)}
+	}
+
+	return NewDefaultMessagesIterator(chatWithMessages)
+}
+
+func buildIndexMap(messages [][]byte) map[string]int {
+	indexMap := make(map[string]int)
+	for i, hash := range messages {
+		hashStr := string(hash)
+		indexMap[hashStr] = i
+	}
+	return indexMap
+}
+
+func (m *MessagesOrderController) sort(chatWithMessages map[transport.Filter][]*types.Message, order messagesOrderType) []*chatWithMessage {
+	allMessages := make([]*chatWithMessage, 0)
+	for chat, messages := range chatWithMessages {
+		for _, message := range messages {
+			allMessages = append(allMessages, &chatWithMessage{chat: chat, message: message})
+		}
+	}
+
+	m.mutex.RLock()
+	indexMap := buildIndexMap(m.messagesInPostOrder)
+	m.mutex.RUnlock()
+
+	sort.SliceStable(allMessages, func(i, j int) bool {
+		indexI, okI := indexMap[string(allMessages[i].message.Hash)]
+		indexJ, okJ := indexMap[string(allMessages[j].message.Hash)]
+
+		if okI && okJ {
+			if order == messagesOrderReversed {
+				return indexI > indexJ
+			}
+			return indexI < indexJ
+		}
+
+		return !okI && okJ // keep messages with unknown hashes at the end
+	})
+
+	return allMessages
+}
+
+type chatWithMessage struct {
+	chat    transport.Filter
+	message *types.Message
+}
+
+type messagesIterator struct {
+	chatWithMessages []*chatWithMessage
+	currentIndex     int
+}
+
+func (it *messagesIterator) HasNext() bool {
+	return it.currentIndex < len(it.chatWithMessages)
+}
+
+func (it *messagesIterator) Next() (transport.Filter, []*types.Message) {
+	if it.HasNext() {
+		m := it.chatWithMessages[it.currentIndex]
+		it.currentIndex++
+		return m.chat, []*types.Message{m.message}
+	}
+
+	return transport.Filter{}, nil
+}