From 5e4d58a8070139f4b26289d0ff791325bc78f684 Mon Sep 17 00:00:00 2001
From: Andrea Maria Piana <andrea.maria.piana@gmail.com>
Date: Thu, 30 Jul 2020 21:14:47 +0200
Subject: [PATCH] Fix lastMessage when receive an emoji out of order

---
 protocol/chat.go      | 10 +++++++---
 protocol/chat_test.go | 31 +++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/protocol/chat.go b/protocol/chat.go
index dcd6124b9..94ee89395 100644
--- a/protocol/chat.go
+++ b/protocol/chat.go
@@ -219,15 +219,19 @@ func (c *Chat) NextClockAndTimestamp(timesource TimeSource) (uint64, uint64) {
 
 func (c *Chat) UpdateFromMessage(message *Message, timesource TimeSource) error {
 	c.Timestamp = int64(timesource.GetCurrentTime())
-	if c.LastClockValue <= message.Clock {
+	higherClock := c.LastClockValue <= message.Clock
+	// If the clock is higher, or last message is nil, we set the message
+	if higherClock || c.LastMessage == nil {
 		jsonMessage, err := json.Marshal(message)
 		if err != nil {
 			return err
 		}
-
-		c.LastClockValue = message.Clock
 		c.LastMessage = jsonMessage
 	}
+	// If the clock is higher we set the clock
+	if higherClock {
+		c.LastClockValue = message.Clock
+	}
 	return nil
 }
 
diff --git a/protocol/chat_test.go b/protocol/chat_test.go
index 45b1ca382..132873d56 100644
--- a/protocol/chat_test.go
+++ b/protocol/chat_test.go
@@ -70,3 +70,34 @@ func (s *ChatTestSuite) TestValidateChat() {
 	}
 
 }
+
+func (s *ChatTestSuite) TestUpdateFromMessage() {
+
+	// Base case, clock is higher
+	message := &Message{}
+	chat := &Chat{}
+
+	message.Clock = 1
+	s.Require().NoError(chat.UpdateFromMessage(message, &testTimeSource{}))
+	s.Require().NotNil(chat.LastMessage)
+	s.Require().Equal(uint64(1), chat.LastClockValue)
+
+	// Clock is lower and lastMessage is not nil
+	message = &Message{}
+	lastMessage := []byte("test")
+	chat = &Chat{LastClockValue: 2, LastMessage: lastMessage}
+
+	message.Clock = 1
+	s.Require().NoError(chat.UpdateFromMessage(message, &testTimeSource{}))
+	s.Require().Equal(lastMessage, chat.LastMessage)
+	s.Require().Equal(uint64(2), chat.LastClockValue)
+
+	// Clock is lower and lastMessage is nil
+	message = &Message{}
+	chat = &Chat{LastClockValue: 2}
+
+	message.Clock = 1
+	s.Require().NoError(chat.UpdateFromMessage(message, &testTimeSource{}))
+	s.Require().NotNil(chat.LastMessage)
+	s.Require().Equal(uint64(2), chat.LastClockValue)
+}