From 6b96b8e4e9ccc110cf36c47a29f504551f81121a Mon Sep 17 00:00:00 2001
From: sacOO7 <sachinshinde7676@gmail.com>
Date: Mon, 30 Oct 2023 18:46:55 +0530
Subject: [PATCH] Added implementation for resending acks without msgserial
 change for successful resume

---
 ably/realtime_client.go | 13 ++++++-------
 ably/realtime_conn.go   | 11 ++++++++++-
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/ably/realtime_client.go b/ably/realtime_client.go
index 752fdfbe..92369f65 100644
--- a/ably/realtime_client.go
+++ b/ably/realtime_client.go
@@ -73,7 +73,7 @@ func (c *Realtime) onChannelMsg(msg *protocolMessage) {
 	c.Channels.Get(msg.Channel).notify(msg)
 }
 
-func (c *Realtime) onReconnected(isNewID bool) {
+func (c *Realtime) onReconnected(failedResumeOrRecover bool) {
 	for _, ch := range c.Channels.Iterate() {
 		switch ch.State() {
 		// RTN15g3, RTN15c6, RTN15c7, RTN16l, RTN19b
@@ -84,20 +84,19 @@ func (c *Realtime) onReconnected(isNewID bool) {
 		}
 	}
 
-	if !isNewID /* RTN15c3, RTN15g3 */ {
+	if failedResumeOrRecover /* RTN15c3, RTN15g3 */ {
 		// No need to reattach: state is preserved. We just need to flush the
 		// queue of pending messages.
 		// TODO - Once channel is attached, channel queue will be flushed
 		// for _, ch := range c.Channels.Iterate() {
 		// 	ch.queue.Flush()
 		// }
-		//RTN19a
+		//RTN19a1
 		c.Connection.resendPending()
-		return
+	} else {
+		//RTN19a2 - successful resume, msgSerial doesn't change
+		c.Connection.resendAcks()
 	}
-
-	//RTN19a
-	c.Connection.resendPending()
 }
 
 func (c *Realtime) onReconnectionFailed(err *errorInfo) {
diff --git a/ably/realtime_conn.go b/ably/realtime_conn.go
index e835fc4b..9137a772 100644
--- a/ably/realtime_conn.go
+++ b/ably/realtime_conn.go
@@ -90,7 +90,7 @@ type connCallbacks struct {
 	// move this up because some implementation details for (RTN15c) requires
 	// access to Channels, and we don't have it here, so we let RealtimeClient do the
 	// work.
-	onReconnected func(isNewID bool)
+	onReconnected func(failedResumeOrRecover bool)
 	// onReconnectionFailed is called when we get a FAILED response from a
 	// reconnection request.
 	onReconnectionFailed func(*errorInfo)
@@ -705,6 +705,15 @@ func (c *Connection) log() logger {
 	return c.auth.log()
 }
 
+func (c *Connection) resendAcks() {
+	c.mtx.Lock()
+	defer c.mtx.Unlock()
+	c.log().Debugf("resending %d messages waiting for ACK/NACK", len(c.pending.queue))
+	for _, v := range c.pending.queue {
+		c.conn.Send(v.msg)
+	}
+}
+
 func (c *Connection) resendPending() {
 	c.mtx.Lock()
 	cx := c.pending.Dismiss()