boxes: Configure private_box_view to send typing status.

This commit captures the user's typing status using urwid's
connect_signal(), observing for changes in the msg_write_box. The
msg_write_box is connected to functions that send start and stop events with
a limit on how frequently the functions can be called. The corresponding
wait periods after the user starts and stops typing are used to restrict
calling the function excessively.

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
@@ -40,6 +40,8 @@ def __init__(self, view: Any) -> None:
         self.stream_id = None  # type: Optional[int]
         self.recipient_user_ids = []  # type: List[int]
         self.msg_body_edit_enabled = True
+        self.send_next_typing_update = datetime.now()
+        self.last_key_update = datetime.now()
         self.FOCUS_CONTAINER_HEADER = 0
         self.FOCUS_HEADER_BOX_RECIPIENT = 0
         self.FOCUS_HEADER_BOX_STREAM = 0
@@ -57,13 +59,19 @@ def main_view(self, new: bool) -> Any:
     def set_editor_mode(self) -> None:
         self.view.controller.enter_editor_mode_with(self)
 
+    def send_stop_typing_status(self) -> None:
+        self.model.send_typing_status_by_user_ids(self.recipient_user_ids,
+                                                  status='stop')
+        self.send_next_typing_update = datetime.now()
+
     def private_box_view(self, button: Any=None, email: str='',
                          recipient_user_ids: Optional[List[int]]=None) -> None:
         self.set_editor_mode()
         if recipient_user_ids:
             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(
@@ -83,6 +91,33 @@ def private_box_view(self, button: Any=None, email: str='',
         ]
         self.focus_position = self.FOCUS_CONTAINER_MESSAGE
 
+        # Typing status is sent in regular intervals to limit the number of
+        # notifications sent. Idleness should also prompt a notification.
+        # Refer to https://zulip.com/api/set-typing-status for the protocol
+        # on typing notifications sent by clients.
+        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: object, new_edit_text: str) -> None:
+            if new_edit_text:
+                self.last_key_update = datetime.now()
+                if self.last_key_update > self.send_next_typing_update:
+                    self.model.send_typing_status_by_user_ids(
+                                self.recipient_user_ids, status='start')
+                    self.send_next_typing_update += start_period_delta
+
+        @asynch
+        def on_idle_send_status(*args: object) -> None:
+            sleep(TYPING_STOPPED_WAIT_PERIOD)
+            if datetime.now() > self.last_key_update + stop_period_delta:
+                self.send_stop_typing_status()
+
+        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 +378,7 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
                         content=self.msg_write_box.edit_text
                     )
             else:
+                self.send_stop_typing_status()
                 if self.msg_edit_id:
                     success = self.model.update_private_message(
                         content=self.msg_write_box.edit_text,
@@ -355,12 +391,14 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
                     )
             if success:
                 self.msg_write_box.edit_text = ''
+                self.send_stop_typing_status()
                 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.send_stop_typing_status()
             self.view.controller.exit_editor_mode()
             self.main_view(False)
             self.view.middle_column.set_focus('body')