boxes: Improve trigger sequence for generic_autocomplete

tests/ui_tools/test_boxes.py

@@ -123,6 +123,24 @@ def test_generic_autocomplete_set_footer(self, mocker, write_box,
         ('@_', 3, None),  # Reached last match
         ('@_', 4, None),  # Beyond end
         ('@_', -1, '@_**Human 2**'),
+        # Complex autocomplete prefixes.
+        ('(@H', 0, '(@**Human Myself**'),
+        ('(@H', 1, '(@**Human 1**'),
+        ('-@G', 0, '-@*Group 1*'),
+        ('-@G', 1, '-@*Group 2*'),
+        ('_@H', 0, '_@**Human Myself**'),
+        ('_@G', 0, '_@*Group 1*'),
+        ('@@H', 0, '@@**Human Myself**'),
+        (':@H', 0, ':@**Human Myself**'),
+        ('#@H', 0, '#@**Human Myself**'),
+        ('@_@H', 0, '@_@**Human Myself**'),
+        ('>@_H', 0, '>@_**Human Myself**'),
+        ('>@_H', 1, '>@_**Human 1**'),
+        ('@_@_H', 0, '@_@_**Human Myself**'),
+        ('@@_H', 0, '@@_**Human Myself**'),
+        (':@_H', 0, ':@_**Human Myself**'),
+        ('#@_H', 0, '#@_**Human Myself**'),
+        ('@@_H', 0, '@@_**Human Myself**'),
     ])
     def test_generic_autocomplete_mentions(self, write_box, text,
                                            required_typeahead, state):
@@ -155,6 +173,13 @@ def test_generic_autocomplete_mentions(self, write_box, text,
         ('#Stream 1', 0, '#**Stream 1**', []),  # Complete match.
         ('#nomatch', 0, None, []),
         ('#ene', 0, None, []),
+        # Complex autocomplete prefixes.
+        ('[#Stream', 0, '[#**Stream 1**', []),
+        ('(#Stream', 1, '(#**Stream 2**', []),
+        ('@#Stream', 0, '@#**Stream 1**', []),
+        ('@_#Stream', 0, '@_#**Stream 1**', []),
+        (':#Stream', 0, ':#**Stream 1**', []),
+        ('##Stream', 0, '##**Stream 1**', []),
         # With 'Secret stream' pinned.
         ('#Stream', 0, '#**Secret stream**',
          [['Secret stream'], ]),  # 2nd-word startswith match (pinned).
@@ -197,6 +222,12 @@ def test_generic_autocomplete_streams(self, write_box, text,
         (':', -1, ':smirk:'),
         (':nomatch', 0, None),
         (':nomatch', -1, None),
+        # Complex autocomplete prefixes.
+        ('(:smi', 0, '(:smile:'),
+        ('&:smi', 1, '&:smiley:'),
+        ('@:smi', 0, '@:smile:'),
+        ('@_:smi', 0, '@_:smile:'),
+        ('#:smi', 0, '#:smile:'),
         ])
     def test_generic_autocomplete_emojis(self, write_box, text,
                                          mocker, state, required_typeahead):

zulipterminal/ui_tools/boxes.py

@@ -102,25 +102,45 @@ def generic_autocomplete(self, text: str, state: Optional[int]
                 (':', self.autocomplete_emojis),
             ])
 
-        for prefix, autocomplete_func in autocomplete_map.items():
-            if text.startswith(prefix):
-                self.is_in_typeahead_mode = True
-                typeaheads, suggestions = autocomplete_func(text, prefix)
-                fewer_typeaheads = typeaheads[:num_suggestions]
-                reduced_suggestions = suggestions[:num_suggestions]
-                is_truncated = len(fewer_typeaheads) != len(typeaheads)
-
-                if (state is not None and state < len(fewer_typeaheads)
-                        and state >= -len(fewer_typeaheads)):
-                    typeahead = fewer_typeaheads[state]  # type: Optional[str]
-                else:
-                    typeahead = None
-                    state = None
-                self.view.set_typeahead_footer(reduced_suggestions,
-                                               state, is_truncated)
-                return typeahead
-
-        return text
+        # Look in a reverse order to find the last autocomplete prefix used in
+        # the text. For instance, if text='@#example', use '#' as the prefix.
+        reversed_text = text[::-1]
+        for reverse_index, char in enumerate(reversed_text):
+            # Patch for silent mentions.
+            if (char == '_' and reverse_index + 1 < len(reversed_text)
+                    and reversed_text[reverse_index + 1] == '@'):
+                char = '@_'
+
+            if char in autocomplete_map:
+                prefix = char
+                autocomplete_func = autocomplete_map[prefix]
+                prefix_index = max(text.rfind(prefix), 0)
+                break
+        else:
+            # Return text if it doesn't have any of the autocomplete prefixes.
+            return text
+
+        # NOTE: The following block only executes if any of the autocomplete
+        # prefixes exist.
+        self.is_in_typeahead_mode = True
+        typeaheads, suggestions = (
+            autocomplete_func(text[prefix_index:], prefix)
+        )
+        fewer_typeaheads = typeaheads[:num_suggestions]
+        reduced_suggestions = suggestions[:num_suggestions]
+        is_truncated = len(fewer_typeaheads) != len(typeaheads)
+
+        if (state is not None and state < len(fewer_typeaheads)
+                and state >= -len(fewer_typeaheads)):
+            typeahead = fewer_typeaheads[state]  # type: Optional[str]
+            if typeahead:
+                typeahead = text[:prefix_index] + typeahead
+        else:
+            typeahead = None
+            state = None
+        self.view.set_typeahead_footer(reduced_suggestions,
+                                       state, is_truncated)
+        return typeahead
 
     def autocomplete_mentions(self, text: str, prefix_string: str
                               ) -> Tuple[List[str], List[str]]: