boxes/regexes: Add stream fences handling in stream+topic autocomplete.

This commit improves support for stream+topic autocomplete done in previous
commit to include stream fences case: `#**stream name**>Topic name`.
                                                     ^^
The current approach uses regex for identifying the last occurence of
required format containing stream fences. The dedicated autocomplete
function remains the same: `autocomplete_stream_and_topic`.

Tests added.

Ticks a checkbox in #448.

tests/ui_tools/test_boxes.py

@@ -84,9 +84,12 @@ def test_not_calling_typing_method_without_recipients(self, mocker, write_box):
             ("#**Stream 1>", 1, True, "#**Stream 1>This is a topic**"),
             ("#**Stream 1>", -1, True, "#**Stream 1>Hello there!**"),
             ("#**Stream 1>", -2, True, "#**Stream 1>This is a topic**"),
+            # Fenced prefix
+            ("#**Stream 1**>T", 0, True, "#**Stream 1>Topic 1**"),
             # Invalid stream
             ("#**invalid stream>", 0, False, None),
             # Invalid prefix format
+            ("#**Stream 1*>", 0, True, None),
             ("#*Stream 1>", 0, True, None),
             ("#Stream 1>", 0, True, None),
             # Complex autocomplete prefixes.
@@ -95,6 +98,7 @@ def test_not_calling_typing_method_without_recipients(self, mocker, write_box):
             ("@#**Stream 1>", 0, True, "@#**Stream 1>Topic 1**"),
             ("@_#**Stream 1>", 0, True, "@_#**Stream 1>Topic 1**"),
             (":#**Stream 1>", 0, True, ":#**Stream 1>Topic 1**"),
+            ("(#**Stream 1**>", 0, True, "(#**Stream 1>Topic 1**"),
         ],
     )
     def test_generic_autocomplete_stream_and_topic(

zulipterminal/config/regexes.py

@@ -17,3 +17,8 @@
     REGEX_STREAM_FENCED_HALF,
     REGEX_TOPIC_NAME,
 )
+# Example text: #**stream name**>Topic name
+REGEX_AUTOCOMPLETE_STREAM_TOPIC_FENCED = r"{}>{}$".format(
+    REGEX_STREAM_FENCED,
+    REGEX_TOPIC_NAME,
+)

zulipterminal/ui_tools/boxes.py

@@ -20,7 +20,10 @@
     keys_for_command,
     primary_key_for_command,
 )
-from zulipterminal.config.regexes import REGEX_AUTOCOMPLETE_STREAM_TOPIC
+from zulipterminal.config.regexes import (
+    REGEX_AUTOCOMPLETE_STREAM_TOPIC,
+    REGEX_AUTOCOMPLETE_STREAM_TOPIC_FENCED,
+)
 from zulipterminal.config.symbols import (
     INVALID_MARKER,
     MESSAGE_CONTENT_MARKER,
@@ -469,10 +472,21 @@ def generic_autocomplete(self, text: str, state: Optional[int]) -> Optional[str]
 
         # Matches autocomplete for stream + topic at the end of a text.
         match = re.search(REGEX_AUTOCOMPLETE_STREAM_TOPIC, text)
+        match_fenced = re.search(REGEX_AUTOCOMPLETE_STREAM_TOPIC_FENCED, text)
         if match:
             prefix = f"#**{match.group(1)}>"
             autocomplete_map.update({prefix: self.autocomplete_stream_and_topic})
             prefix_indices[prefix] = match.start()
+        elif match_fenced:
+            # Amending the prefix to remove stream fence `**`
+            prefix = f"#**{match_fenced.group(1)}>"
+            prefix_with_topic = prefix + match_fenced.group(2)
+
+            autocomplete_map.update({prefix: self.autocomplete_stream_and_topic})
+            prefix_indices[prefix] = match_fenced.start()
+
+            # Amending the text to have new prefix (without `**` fence)
+            text = text[: match_fenced.start()] + prefix_with_topic
 
         found_prefix_indices = {
             prefix: index for prefix, index in prefix_indices.items() if index > -1