boxes: Improve trigger sequence for generic_autocomplete.

Updated generic_autocomplete along with its autocomplete_mentions/
streams to provide typeahead even when there are some characters
before their respective trigger character.

Tests amended.

Fixes #541.

Author: preetmishra

tests/ui_tools/test_boxes.py

@@ -29,6 +29,9 @@ def test_init(self, write_box):
         ('@_Boo', '@_', 1),
         ('Plain Text', '', 0),
         ('Plain Text', '', 1),
+        ('(@Boo', '@', 0),
+        ('(@_Boo', '@_', 0),
+        ('(', '', 0),
     ])
     def test_generic_autocomplete(self, mocker, write_box, text,
                                   prefix_string, state):
@@ -93,6 +96,13 @@ def test_generic_autocomplete(self, mocker, write_box, text,
         ('@_', 3, '@_', None),  # Reached last match
         ('@_', 4, '@_', None),  # Beyond end
         ('@_', -1, '@_', '@_**Human 2**'),
+        # When some character is preceding the prefix_string (trigger).
+        ('(@H', 0, '@', '(@**Human Myself**'),
+        ('(@H', 1, '@', '(@**Human 1**'),
+        ('(@_H', 0, '@_', '(@_**Human Myself**'),
+        ('(@_H', 1, '@_', '(@_**Human 1**'),
+        ('(@G', 0, '@', '(@*Group 1*'),
+        ('(@G', 1, '@', '(@*Group 2*'),
     ])
     def test_autocomplete_mentions(self, write_box, users_fixture,
                                    text, state, prefix_string,
@@ -125,7 +135,9 @@ def test_autocomplete_mentions(self, write_box, users_fixture,
         ('#St', 1, '#', '#**Stream 2**'),
         ('#Stream 1', 0, '#', '#**Stream 1**'),
         ('No match', 0, '#', None),
-        ('No match', -1, '#', None)
+        ('No match', -1, '#', None),
+        ('(#Stream', 0, '#', '(#**Stream 1**'),
+        ('(#Stream', 1, '#', '(#**Stream 2**'),
     ])
     def test_autocomplete_streams(self, write_box, streams_fixture,
                                   text, state, prefix_string,

zulipterminal/ui_tools/boxes.py

@@ -94,11 +94,11 @@ def stream_box_view(self, caption: str='', title: str='') -> None:
         self.contents = write_box
 
     def generic_autocomplete(self, text: str, state: int) -> Optional[str]:
-        if text.startswith('@_'):
+        if '@_' in text:
             return self.autocomplete_mentions(text, state, '@_')
-        elif text.startswith('@'):
+        elif '@' in text:
             return self.autocomplete_mentions(text, state, '@')
-        elif text.startswith('#'):
+        elif '#' in text:
             return self.autocomplete_streams(text, state, '#')
         else:
             return text
@@ -107,28 +107,33 @@ def autocomplete_mentions(self, text: str, state: int,
                               prefix_string: str) -> Optional[str]:
         # Handles user mentions (@ mentions and silent mentions)
         # and group mentions.
+        prefix_index = max(text.find(prefix_string), 0)
         group_typeahead = [prefix_string+'*{}*'.format(group_name)
                            for group_name in self.model.user_group_names
-                           if match_groups(group_name, text[1:])]
+                           if match_groups(group_name, text[prefix_index+1:])]
 
         users_list = self.view.users
         user_typeahead = [prefix_string+'**{}**'.format(user['full_name'])
                           for user in users_list
-                          if match_user(user, text[len(prefix_string):])]
+                          if match_user(
+                              user, text[len(prefix_string)+prefix_index:])]
         combined_typeahead = group_typeahead + user_typeahead
         try:
-            return combined_typeahead[state]
+            return text[:prefix_index] + combined_typeahead[state]
         except (IndexError, TypeError):
             return None
 
     def autocomplete_streams(self, text: str, state: int,
                              prefix_string: str) -> Optional[str]:
+        prefix_index = max(text.find(prefix_string), 0)
         streams_list = self.view.pinned_streams + self.view.unpinned_streams
         stream_typeahead = [prefix_string+'**{}**'.format(stream[0])
                             for stream in streams_list
-                            if match_stream(stream, text[len(prefix_string):])]
+                            if match_stream(
+                                stream, text[len(prefix_string)
+                                             + prefix_index:])]
         try:
-            return stream_typeahead[state]
+            return text[:prefix_index] + stream_typeahead[state]
         except (IndexError, TypeError):
             return None