core/keys/views: Introduce EditHistoryView for edit history.

This, essentially, lays the groundwork for 'edit history' feature.

Author: shreyamalviya

zulipterminal/config/keys.py

@@ -205,6 +205,12 @@
         'help_text': 'View message information',
         'key_category': 'msg_actions',
     }),
+    ('EDIT_HISTORY', {
+        'keys': {'d'},
+        'help_text': 'View edit history from message information box',
+        'excluded_from_random_tips': True,
+        'key_category': 'msg_actions',
+    }),
     ('STREAM_DESC', {
         'keys': {'i'},
         'help_text': 'View stream description',

zulipterminal/core.py

@@ -15,7 +15,8 @@
 from zulipterminal.ui import Screen, View
 from zulipterminal.ui_tools.utils import create_msg_box_list
 from zulipterminal.ui_tools.views import (
-    HelpView, MsgInfoView, NoticeView, PopUpConfirmationView, StreamInfoView,
+    EditHistoryView, HelpView, MsgInfoView, NoticeView, PopUpConfirmationView,
+    StreamInfoView,
 )
 from zulipterminal.version import ZT_VERSION
 
@@ -124,6 +125,10 @@ def show_stream_info(self, color: str, name: str, desc: str) -> None:
     def popup_with_message(self, text: str, width: int, height: int) -> None:
         self.show_pop_up(NoticeView(self, text, width, height), "NOTICE")
 
+    def show_edit_history(self, msg: Any) -> None:
+        self.show_pop_up(EditHistoryView(self, msg),
+                         'Edit History (up/down scrolls)')
+
     def search_messages(self, text: str) -> None:
         # Search for a text in messages
         self.model.index['search'].clear()

zulipterminal/ui_tools/views.py

@@ -6,7 +6,7 @@
 import urwid
 
 from zulipterminal.config.keys import (
-    HELP_CATEGORIES, KEY_BINDINGS, is_command_key,
+    HELP_CATEGORIES, KEY_BINDINGS, is_command_key, keys_for_command,
 )
 from zulipterminal.helper import Message, asynch, match_user
 from zulipterminal.ui_tools.boxes import PanelSearchBox
@@ -904,6 +904,9 @@ def __init__(self, controller: Any, msg: Message) -> None:
             ('Date & Time', time.ctime(msg['timestamp'])[:-5]),
             ('Sender', msg['sender_full_name']),
             ('Sender\'s Email ID', msg['sender_email']),
+            ('Edit History',
+             'Press ' + ', '.join(map(repr, keys_for_command('EDIT_HISTORY')))
+             + ' to view'),
             ('Reactions', reactions if msg['reactions'] else '---None---'),
             ])
 
@@ -925,3 +928,24 @@ def __init__(self, controller: Any, msg: Message) -> None:
              for index, (field, data) in enumerate(msg_info.items())]
 
         super().__init__(controller, msg_info_content, 'MSG_INFO')
+
+    def keypress(self, size: urwid_Size, key: str) -> str:
+        if is_command_key('EDIT_HISTORY', key):
+            self.controller.show_edit_history(self.msg)
+        return super().keypress(size, key)
+
+
+class EditHistoryView(PopUpView):
+    def __init__(self, controller: Any, msg: Any) -> None:
+        self.controller = controller
+        self.msg = msg
+        self.width = 64
+        self.height = 0
+        super().__init__(controller, [], 'MSG_INFO')
+
+    def keypress(self, size: urwid_Size, key: str) -> str:
+        if (is_command_key('GO_BACK', key)
+                or is_command_key('EDIT_HISTORY', key)):
+            self.controller.show_msg_info(self.msg)
+            return key
+        return super().keypress(size, key)