From 535423398ae83f2287812048fb3308783a4702f3 Mon Sep 17 00:00:00 2001
From: Bohdan Horbeshko <bodqhrohro@gmail.com>
Date: Sun, 9 Aug 2026 14:16:20 -0400
Subject: [PATCH] Improve thread safety of resource map

---
 telegram/connect.go |  7 ++++---
 telegram/utils.go   | 35 ++++++++++++++++-------------------
 2 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/telegram/connect.go b/telegram/connect.go
index 207fcd6..696a34f 100644
--- a/telegram/connect.go
+++ b/telegram/connect.go
@@ -235,9 +235,10 @@ func (c *Client) Disconnect(resource string, quit bool) bool {
 		c.deleteResource(resource)
 	}
 	// other resources are still active
-	if (len(c.resources) > 0 || c.Session.KeepOnline) && !quit {
-		log.Infof("Resource %v for account %v has disconnected, %v remaining", resource, c.Session.Login, len(c.resources))
-		log.Debugf("Resources: %#v", c.resources)
+	remaining := c.resourcesSnapshot()
+	if (len(remaining) > 0 || c.Session.KeepOnline) && !quit {
+		log.Infof("Resource %v for account %v has disconnected, %v remaining", resource, c.Session.Login, len(remaining))
+		log.Debugf("Resources: %#v", remaining)
 		return false
 	}
 	// already disconnected
diff --git a/telegram/utils.go b/telegram/utils.go
index 33acb4e..644bde3 100644
--- a/telegram/utils.go
+++ b/telegram/utils.go
@@ -1928,7 +1928,7 @@ func (c *Client) SendMessageToGateway(chatId int64, message *client.Message, id
 				sha1 := c.GetPhotoSha1(chat.Photo.Small, chatId)
 				size := c.GetPhotoSize(chat.Photo.Small)
 
-				for resource := range c.resourcesRange() {
+				for _, resource := range c.resourcesSnapshot() {
 					features, ok := c.XmppClientFeatures[resource]
 					if ok && features != nil {
 						for _, feature := range *features {
@@ -2388,23 +2388,20 @@ func (c *Client) deleteResource(resource string) {
 	}
 }
 
-func (c *Client) resourcesRange() chan string {
+// resourcesSnapshot copies the currently known resources under the lock, so
+// callers can safely iterate/send without holding resourcesLock for the
+// whole operation (which used to block concurrent addResource/deleteResource
+// for as long as a caller's loop body took, e.g. a whole batch of network
+// sends).
+func (c *Client) resourcesSnapshot() []string {
 	c.locks.resourcesLock.Lock()
+	defer c.locks.resourcesLock.Unlock()
 
-	resourceChan := make(chan string, 1)
-
-	go func() {
-		defer func() {
-			c.locks.resourcesLock.Unlock()
-			close(resourceChan)
-		}()
-
-		for resource := range c.resources {
-			resourceChan <- resource
-		}
-	}()
-
-	return resourceChan
+	resources := make([]string, 0, len(c.resources))
+	for resource := range c.resources {
+		resources = append(resources, resource)
+	}
+	return resources
 }
 
 // resend statuses to (to another resource, for example)
@@ -2800,7 +2797,7 @@ func (c *Client) subscribeToID(id int64, chat *client.Chat, firstTime bool) {
 	if chat != nil {
 		if c.Session.MUC && c.IsGroup(chat) {
 			if firstTime {
-				for resource := range c.resourcesRange() {
+				for _, resource := range c.resourcesSnapshot() {
 					gateway.InviteToMUC(id, c.jid+"/"+resource, c.xmpp)
 				}
 			}
@@ -2933,7 +2930,7 @@ func (c *Client) getFromOutbox(xmppId string) string {
 func (c *Client) GetCarbonFullJids(isOutgoing bool, ignoredResource string, forceFull bool) []string {
 	var jids []string
 	if isOutgoing {
-		for resource := range c.resourcesRange() {
+		for _, resource := range c.resourcesSnapshot() {
 			if ignoredResource == "" || resource != ignoredResource {
 				jids = append(jids, c.jid+"/"+resource)
 			}
@@ -3317,7 +3314,7 @@ func (c *Client) MigrateToMUCs() {
 
 	for _, chatID := range chatIDs {
 		c.unsubscribe(chatID)
-		for resource := range c.resourcesRange() {
+		for _, resource := range c.resourcesSnapshot() {
 			gateway.InviteToMUC(chatID, c.jid+"/"+resource, c.xmpp)
 		}
 	}