model: Add stream wrap-around behavior to next unread topic algorithm.

This commit aims to introduce in-stream wrap-around behavior to the
next_unread_topic_from_message_id function if there are unread messages
still present in the current stream.

Test case added.

tests/model/test_model.py

@@ -4010,6 +4010,12 @@ def test_is_muted_topic(
                 (1, "topic1"),
                 id="unmuted_unread_not_present_in_next_stream_as_current_topic_not_in_unread_list",
             ),
+            case(
+                {(1, "topic1"), (1, "topic11"), (2, "topic2")},
+                (1, "topic11"),
+                (1, "topic1"),
+                id="unread_present_in_same_stream_wrap_around",
+            ),
         ],
     )
     def test_get_next_unread_topic(

zulipterminal/model.py

@@ -907,6 +907,7 @@ def next_unread_topic_from_message_id(
         current_topic = self.stream_topic_from_message_id(current_message)
         unread_topics = sorted(self.unread_counts["unread_topics"].keys())
         next_topic = False
+        stream_start = None
         if current_topic is None:
             next_topic = True
         elif current_topic not in unread_topics:
@@ -919,14 +920,27 @@ def next_unread_topic_from_message_id(
         # the last valid unread_topic in unread_topics list.
         for unread_topic in unread_topics * 2:
             stream_id, topic_name = unread_topic
-            if (
-                not self.is_muted_topic(stream_id, topic_name)
-                and not self.is_muted_stream(stream_id)
-                and next_topic
-            ):
-                if unread_topic == current_topic:
-                    return None
-                return unread_topic
+            if not self.is_muted_topic(
+                stream_id, topic_name
+            ) and not self.is_muted_stream(stream_id):
+                if next_topic:
+                    if unread_topic == current_topic:
+                        return None
+                    elif (
+                        current_topic is None
+                        or unread_topic[0] == current_topic[0]
+                        or stream_start == current_topic
+                    ):
+                        return unread_topic
+                    else:
+                        return stream_start
+
+                if (
+                    not stream_start
+                    and current_topic is not None
+                    and unread_topic[0] == current_topic[0]
+                ):
+                    stream_start = unread_topic
             if unread_topic == current_topic:
                 next_topic = True
         return None