boxes: Configure private_box_view to send typing event.

The user's typing status is captured using urwid's connect_signal(), observing for changes in the msg_write_box. This commit adds signals and functions that the signals call, to send start and stop events in accordance with the wait periods after the user starts and stops typing.

Fixes #593.

Author: prah23

zulipterminal/ui_tools/boxes.py

@@ -1,9 +1,9 @@
 import re
 import unicodedata
 from collections import OrderedDict, defaultdict
-from datetime import date, datetime
+from datetime import date, datetime, timedelta
 from sys import platform
-from time import ctime, time
+from time import ctime, sleep, time
 from typing import Any, Callable, Dict, List, Optional, Tuple, Union
 from urllib.parse import urljoin, urlparse
 
@@ -22,7 +22,7 @@
     STREAM_TOPIC_SEPARATOR, TIME_MENTION_MARKER,
 )
 from zulipterminal.helper import (
-    Message, format_string, match_emoji, match_group, match_stream,
+    Message, asynch, format_string, match_emoji, match_group, match_stream,
     match_topics, match_user,
 )
 from zulipterminal.ui_tools.buttons import EditModeButton
@@ -57,6 +57,7 @@ def private_box_view(self, button: Any=None, email: str='',
             self.recipient_user_ids = recipient_user_ids
         if email == '' and button is not None:
             email = button.email
+        self.send_next_typing_update = datetime.now()
         self.to_write_box = ReadlineEdit("To: ", edit_text=email)
         self.msg_write_box = ReadlineEdit(multiline=True)
         self.msg_write_box.enable_autocomplete(
@@ -75,6 +76,29 @@ def private_box_view(self, button: Any=None, email: str='',
         ]
         self.focus_position = 1
 
+        TYPING_STARTED_WAIT_PERIOD = 10
+        TYPING_STOPPED_WAIT_PERIOD = 5
+
+        start_period_delta = timedelta(seconds=TYPING_STARTED_WAIT_PERIOD)
+        stop_period_delta = timedelta(seconds=TYPING_STOPPED_WAIT_PERIOD)
+
+        def on_type_send_status(edit: str, new_edit_text: str) -> None:
+            if not new_edit_text == "":
+                current_time = datetime.now()
+                self.LAST_TYPE_UPDATE = datetime.now()
+                if current_time > self.send_next_typing_update:
+                    self.model.send_typing_event(self.recipient_user_ids, True)
+                    self.send_next_typing_update += start_period_delta
+
+        @asynch
+        def on_idle_send_status(*args: str) -> None:
+            sleep(TYPING_STOPPED_WAIT_PERIOD)
+            if datetime.now() > self.LAST_TYPE_UPDATE + stop_period_delta:
+                self.model.send_typing_event(self.recipient_user_ids, False)
+
+        urwid.connect_signal(self.msg_write_box, 'change', on_type_send_status)
+        urwid.connect_signal(self.msg_write_box, 'change', on_idle_send_status)
+
     def stream_box_view(self, stream_id: int, caption: str='', title: str='',
                         ) -> None:
         self.set_editor_mode()
@@ -343,6 +367,8 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
                         content=self.msg_write_box.edit_text
                     )
             else:
+                self.model.send_typing_event(self.recipient_user_ids, False)
+                self.send_next_typing_update = datetime.now()
                 if self.msg_edit_id:
                     success = self.model.update_private_message(
                         content=self.msg_write_box.edit_text,
@@ -355,12 +381,15 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
                     )
             if success:
                 self.msg_write_box.edit_text = ''
+                self.model.send_typing_event(self.recipient_user_ids, False)
+                self.send_next_typing_update = datetime.now()
                 if self.msg_edit_id:
                     self.msg_edit_id = None
                     self.keypress(size, 'esc')
         elif is_command_key('GO_BACK', key):
             self.msg_edit_id = None
             self.msg_body_edit_enabled = True
+            self.model.send_typing_event(self.recipient_user_ids, False)
             self.view.controller.exit_editor_mode()
             self.main_view(False)
             self.view.middle_column.set_focus('body')