boxes: Add warning when sending message to announcement streams

Normal users are not allowed to send messages in announcement streams,
currently when an unauthorised user sends message to this stream, nothing happens.
This commit changes this behaviour and adds a footer warning for the same.

Fixes: #682

Author: imnitishng

zulipterminal/ui_tools/boxes.py

@@ -58,38 +58,43 @@ def private_box_view(self, button: Any=None, email: str='') -> None:
         self.focus_position = 1
 
     def stream_box_view(self, caption: str='', title: str='') -> None:
-        self.set_editor_mode()
-        self.to_write_box = None
-        self.msg_write_box = ReadlineEdit(multiline=True)
-        self.msg_write_box.enable_autocomplete(
-            func=self.generic_autocomplete,
-            key=keys_for_command('AUTOCOMPLETE').pop(),
-            key_reverse=keys_for_command('AUTOCOMPLETE_REVERSE').pop()
-        )
-        self.stream_write_box = ReadlineEdit(
-            caption="Stream:  ",
-            edit_text=caption
-        )
-        self.title_write_box = ReadlineEdit(caption="Topic:  ",
-                                            edit_text=title)
-
-        header_write_box = urwid.Columns([
-            urwid.LineBox(
-                self.stream_write_box, tlcorner='─', tline='─', lline='',
-                trcorner='┬', blcorner='─', rline='│',
-                bline='─', brcorner='┴'
-            ),
-            urwid.LineBox(
-                self.title_write_box, tlcorner='─', tline='─', lline='',
-                trcorner='─', blcorner='─', rline='',
-                bline='─', brcorner='─'
-            ),
-        ])
-        write_box = [
-            (header_write_box, self.options()),
-            (self.msg_write_box, self.options()),
-        ]
-        self.contents = write_box
+        if self.model.stream_dict[self.model.stream_id].get(
+                'is_announcement_only', None) == 1:
+            self.msg_footer = self.view.set_footer_text(
+                "You are not authorised to send messages to this stream.", 5)
+        else:
+            self.set_editor_mode()
+            self.to_write_box = None
+            self.msg_write_box = ReadlineEdit(multiline=True)
+            self.msg_write_box.enable_autocomplete(
+                func=self.generic_autocomplete,
+                key=keys_for_command('AUTOCOMPLETE').pop(),
+                key_reverse=keys_for_command('AUTOCOMPLETE_REVERSE').pop()
+            )
+            self.stream_write_box = ReadlineEdit(
+                caption="Stream:  ",
+                edit_text=caption
+            )
+            self.title_write_box = ReadlineEdit(caption="Topic:  ",
+                                                edit_text=title)
+
+            header_write_box = urwid.Columns([
+                urwid.LineBox(
+                    self.stream_write_box, tlcorner='─', tline='─', lline='',
+                    trcorner='┬', blcorner='─', rline='│',
+                    bline='─', brcorner='┴'
+                ),
+                urwid.LineBox(
+                    self.title_write_box, tlcorner='─', tline='─', lline='',
+                    trcorner='─', blcorner='─', rline='',
+                    bline='─', brcorner='─'
+                ),
+            ])
+            write_box = [
+                (header_write_box, self.options()),
+                (self.msg_write_box, self.options()),
+            ]
+            self.contents = write_box
 
     def generic_autocomplete(self, text: str, state: int) -> Optional[str]:
         autocomplete_map = OrderedDict([