feat: support option to mark messages unread by message timestamp

channel.go

@@ -701,8 +701,9 @@ func (ch *Channel) MarkRead(ctx context.Context, userID string, options ...MarkR
 }
 
 type markUnreadOption struct {
-	MessageID string `json:"message_id"`
-	ThreadID  string `json:"thread_id"`
+	MessageID        string    `json:"message_id"`
+	ThreadID         string    `json:"thread_id"`
+	MessageTimestamp time.Time `json:"message_timestamp"`
 
 	UserID string `json:"user_id"`
 }
@@ -722,6 +723,12 @@ func MarkUnreadThread(id string) func(*markUnreadOption) {
 	}
 }
 
+func MarkUnreadFromTimestamp(timestamp time.Time) func(*markUnreadOption) {
+	return func(opt *markUnreadOption) {
+		opt.MessageTimestamp = timestamp
+	}
+}
+
 // MarkUnread message or thread (not both) for specified user.
 func (ch *Channel) MarkUnread(ctx context.Context, userID string, options ...MarkUnreadOption) (*Response, error) {
 	if userID == "" {

channel_test.go

@@ -993,3 +993,50 @@ func TestChannel_MessageCount_Disabled(t *testing.T) {
 	// message_count should be nil when CountMessages is disabled
 	assert.Nil(t, ch.MessageCount, "message_count should be nil when CountMessages is disabled")
 }
+
+func TestChannel_MarkUnread(t *testing.T) {
+	c := initClient(t)
+	ctx := context.Background()
+	user1 := randomUser(t, c)
+	user2 := randomUser(t, c)
+	ch := initChannel(t, c, user1.ID, user2.ID)
+
+	t.Run("successful mark unread with message ID", func(t *testing.T) {
+		// Send a message first
+		msgResp, err := ch.SendMessage(ctx, &Message{Text: "test message"}, user2.ID)
+		require.NoError(t, err, "send message should not return an error")
+
+		resp, err := ch.MarkUnread(ctx, user1.ID, MarkUnreadFromMessage(msgResp.Message.ID))
+		require.NoError(t, err, "mark unread with message ID should not return an error")
+		require.NotNil(t, resp, "response should not be nil")
+	})
+
+	t.Run("successful mark unread with thread ID", func(t *testing.T) {
+		// Send a message first
+		msgResp, err := ch.SendMessage(ctx, &Message{Text: "parent message"}, user2.ID)
+		require.NoError(t, err, "send message should not return an error")
+
+		// Send a reply to create a thread
+		replyResp, err := ch.SendMessage(ctx, &Message{Text: "reply", ParentID: msgResp.Message.ID}, user1.ID)
+		require.NoError(t, err, "send reply should not return an error")
+		require.NotEmpty(t, replyResp.Message.ID, "reply should have an ID")
+
+		resp, err := ch.MarkUnread(ctx, user2.ID, MarkUnreadThread(msgResp.Message.ID))
+		require.NoError(t, err, "mark unread with thread ID should not return an error")
+		require.NotNil(t, resp, "response should not be nil")
+	})
+
+	t.Run("successful mark unread with timestamp", func(t *testing.T) {
+		timestamp := time.Now().Add(-1 * time.Hour)
+		resp, err := ch.MarkUnread(ctx, user1.ID, MarkUnreadFromTimestamp(timestamp))
+		require.NoError(t, err, "mark unread with timestamp should not return an error")
+		require.NotNil(t, resp, "response should not be nil")
+	})
+
+	t.Run("error when userID is empty", func(t *testing.T) {
+		resp, err := ch.MarkUnread(ctx, "")
+		require.Error(t, err, "mark unread with empty userID should return an error")
+		require.Nil(t, resp, "response should be nil on error")
+		require.Contains(t, err.Error(), "user ID must be not empty", "error message should mention user ID")
+	})
+}