buttons: Add support for PM narrow in MessageLinkButton.

Helper method added:
 *_decode_pm_data().

The near parameter is used to set focus to a particular message (using
the anchor) while switching narrow.

Tests added and amended.

Author: Ezio-Sarthak

tests/ui_tools/test_buttons.py

@@ -1,6 +1,7 @@
 from typing import Any, Dict
 
 import pytest
+from typing_extensions import Literal
 from urwid import AttrMap, Overlay
 
 from zulipterminal.config.keys import keys_for_command
@@ -405,6 +406,21 @@ def test__decode_stream_data(self, stream_data, expected_response):
 
         assert return_value == expected_response
 
+    @pytest.mark.parametrize('pm_data, expected_response', [
+            ('1,2-pm', dict(recipient_ids=[1, 2], type=Literal['pm'])),
+            ('1,2,3-group', dict(recipient_ids=[1, 2, 3],
+                                 type=Literal['group'])),
+        ],
+        ids=[
+            'ordinary_pm',
+            'group_pm',
+        ]
+    )
+    def test__decode_pm_data(self, pm_data, expected_response):
+        return_value = MessageLinkButton._decode_pm_data(pm_data)
+
+        assert return_value == expected_response
+
     @pytest.mark.parametrize('message_id, expected_return_value', [
         ('1', 1),
         ('foo', None),
@@ -430,6 +446,9 @@ def test__decode_message_id(self, message_id, expected_return_value):
         (SERVER_URL + '/#narrow/stream/1-Stream-1/topic/foo/near/1',
          {'narrow': 'stream:topic:near', 'topic_name': 'foo', 'message_id': 1,
           'stream': {'stream_id': 1, 'stream_name': None}}),
+        (SERVER_URL + '/#narrow/pm-with/1,2-pm/near/1',
+         {'narrow': 'pm-with', 'message_id': 1,
+          'pm_with': {'type': Literal['pm'], 'recipient_ids': [1, 2]}}),
         (SERVER_URL + '/#narrow/foo',
          {}),
         (SERVER_URL + '/#narrow/stream/',
@@ -447,6 +466,7 @@ def test__decode_message_id(self, message_id, expected_return_value):
             'topic_narrow_link',
             'stream_near_narrow_link',
             'topic_near_narrow_link',
+            'pm_near_narrow_link',
             'invalid_narrow_link_1',
             'invalid_narrow_link_2',
             'invalid_narrow_link_3',
@@ -629,44 +649,62 @@ def test__validate_and_patch_stream_data(self, stream_dict, parsed_link,
             'parsed_link',
             'narrow_to_stream_called',
             'narrow_to_topic_called',
+            'narrow_to_user_called',
         ],
         [
             ({'narrow': 'stream',
               'stream': {'stream_id': 1, 'stream_name': 'Stream 1'}},
              True,
+             False,
              False),
             ({'narrow': 'stream:topic', 'topic_name': 'Foo',
               'stream': {'stream_id': 1, 'stream_name': 'Stream 1'}},
              False,
-             True),
+             True,
+             False),
             ({'narrow': 'stream:near', 'message_id': 1,
               'stream': {'stream_id': 1, 'stream_name': 'Stream 1'}},
              True,
+             False,
              False),
             ({'narrow': 'stream:topic:near', 'topic_name': 'Foo',
               'message_id': 1,
               'stream': {'stream_id': 1, 'stream_name': 'Stream 1'}},
              False,
+             True,
+             False),
+            ({'narrow': 'pm-with', 'message_id': 1,
+              'pm_with': {'type': Literal['pm'], 'recipient_ids': [1, 2]}},
+             False,
+             False,
              True),
         ],
         ids=[
             'stream_narrow',
             'topic_narrow',
             'stream_near_narrow',
             'topic_near_narrow',
+            'pm_near_narrow',
         ]
     )
     def test__switch_narrow_to(self, parsed_link, narrow_to_stream_called,
-                               narrow_to_topic_called,
+                               narrow_to_topic_called, narrow_to_user_called
                                ):
         mocked_button = self.message_link_button()
+        # For PM narrow switch
+        mocked_button.model.user_id_email_dict = {
+            1: '[email protected]',
+            2: '[email protected]',
+        }
 
         mocked_button._switch_narrow_to(parsed_link)
 
         assert (mocked_button.controller.narrow_to_stream.called
                 == narrow_to_stream_called)
         assert (mocked_button.controller.narrow_to_topic.called
                 == narrow_to_topic_called)
+        assert (mocked_button.controller.narrow_to_user.called
+                == narrow_to_user_called)
 
     @pytest.mark.parametrize(['error', 'set_footer_text_called',
                               '_switch_narrow_to_called',

zulipterminal/ui_tools/buttons.py

@@ -1,9 +1,9 @@
 import re
-from typing import Any, Callable, Dict, Optional, Tuple, Union, cast
+from typing import Any, Callable, Dict, List, Optional, Tuple, Union, cast
 from urllib.parse import urljoin, urlparse
 
 import urwid
-from typing_extensions import TypedDict
+from typing_extensions import Literal, TypedDict
 
 from zulipterminal.config.keys import is_command_key, primary_key_for_command
 from zulipterminal.config.symbols import (
@@ -277,11 +277,17 @@ def __init__(self, user_id: int, email: str) -> None:
     'stream_name': Optional[str],
 })
 
+DecodedPM = TypedDict('DecodedPM', {
+    'type': Literal['pm', 'group'],
+    'recipient_ids': List[int],
+})
+
 ParsedNarrowLink = TypedDict('ParsedNarrowLink', {
     'narrow': str,
     'stream': DecodedStream,
     'topic_name': str,
     'message_id': Optional[int],
+    'pm_with': DecodedPM,
 }, total=False)
 
 
@@ -331,6 +337,17 @@ def _decode_stream_data(encoded_stream_data: str) -> DecodedStream:
             stream_name = hash_util_decode(encoded_stream_data)
             return DecodedStream(stream_id=None, stream_name=stream_name)
 
+    @staticmethod
+    def _decode_pm_data(encoded_pm_data: str) -> DecodedPM:
+        """
+        Returns a dict with PM type and IDs of PM recipients.
+        """
+        recipient_ids, pm_type = encoded_pm_data.split('-')
+        recipient_ids_list = list(map(int, recipient_ids.split(',')))
+
+        return DecodedPM(type=Literal[pm_type],
+                         recipient_ids=recipient_ids_list)
+
     @staticmethod
     def _decode_message_id(message_id: str) -> Optional[int]:
         """
@@ -356,6 +373,7 @@ def _parse_narrow_link(cls, link: str) -> ParsedNarrowLink:
         #    {encoded.20topic.20name}
         # d. narrow/stream/[{stream_id}-]{stream-name}/topic/
         #    {encoded.20topic.20name}/near/{message_id}
+        # e. narrow/pm-with/[{recipient_ids},]{pm-type}/near/{message_id}
         fragments = urlparse(link.rstrip('/')).fragment.split('/')
         len_fragments = len(fragments)
         parsed_link = ParsedNarrowLink()
@@ -386,6 +404,12 @@ def _parse_narrow_link(cls, link: str) -> ParsedNarrowLink:
             parsed_link = dict(narrow='stream:topic:near', stream=stream_data,
                                topic_name=topic_name, message_id=message_id)
 
+        elif len_fragments == 5 and fragments[1] == 'pm-with':
+            pm_data = cls._decode_pm_data(fragments[2])
+            message_id = cls._decode_message_id(fragments[4])
+            parsed_link = dict(narrow='pm-with', pm_with=pm_data,
+                               message_id=message_id)
+
         return parsed_link
 
     def _validate_and_patch_stream_data(self,
@@ -475,6 +499,13 @@ def _switch_narrow_to(self, parsed_link: ParsedNarrowLink) -> None:
             self.topic_name = parsed_link['topic_name']
             self.message = dict(id=parsed_link['message_id'])
             self.controller.narrow_to_topic(self)
+        elif 'pm-with' == narrow:
+            self.message = dict(id=parsed_link['message_id'])
+            self.recipients_emails = ', '.join(list(
+                self.model.user_id_email_dict.get(user_id)
+                for user_id in parsed_link['pm_with']['recipient_ids']
+            ))
+            self.controller.narrow_to_user(self)
 
     def handle_narrow_link(self) -> None:
         """