refactor: views: Introduce PopUpView class to extract keypress method.

Added PopUpView, a base class for popups, that extracts the common
keypress method and inherited it in HelpView.

This class can be leveraged to introduce the keypress method and
reduce potential code duplication in other popup views.

Test added for PopUpView.

Author: preetmishra

tests/ui/test_ui_tools.py

@@ -5,16 +5,16 @@
 from bs4 import BeautifulSoup
 from urwid import AttrWrap, Columns, Padding, Text
 
-from zulipterminal.config.keys import keys_for_command
+from zulipterminal.config.keys import is_command_key, keys_for_command
 from zulipterminal.helper import powerset
 from zulipterminal.ui_tools.boxes import MessageBox
 from zulipterminal.ui_tools.buttons import (
     StreamButton, TopButton, TopicButton, UserButton,
 )
 from zulipterminal.ui_tools.views import (
     HelpView, LeftColumnView, MessageView, MiddleColumnView, ModListWalker,
-    MsgInfoView, PopUpConfirmationView, RightColumnView, StreamsView,
-    TopicsView, UsersView,
+    MsgInfoView, PopUpConfirmationView, PopUpView, RightColumnView,
+    StreamsView, TopicsView, UsersView,
 )
 
 
@@ -1093,6 +1093,56 @@ def test_topics_view(self, mocker, stream_button, width=40):
         ])
 
 
+class TestPopUpView:
+    @pytest.fixture(autouse=True)
+    def pop_up_view(self, mocker):
+        self.controller = mocker.Mock()
+        self.command = 'COMMAND'
+        self.widget = mocker.Mock()
+        self.widgets = [self.widget, ]
+        self.list_walker = mocker.patch(VIEWS + '.urwid.SimpleFocusListWalker',
+                                        return_value=[])
+        self.super_init = mocker.patch(VIEWS + '.urwid.ListBox.__init__')
+        self.super_keypress = mocker.patch(VIEWS + '.urwid.ListBox.keypress')
+        self.pop_up_view = PopUpView(self.controller, self.widgets,
+                                     self.command)
+
+    def test_init(self):
+        assert self.pop_up_view.controller == self.controller
+        assert self.pop_up_view.command == self.command
+        self.list_walker.assert_called_once_with(self.widgets)
+        self.super_init.assert_called_once_with(self.pop_up_view.log)
+
+    @pytest.mark.parametrize('key', keys_for_command('GO_BACK'))
+    def test_keypress_GO_BACK(self, key):
+        size = (200, 20)
+        self.pop_up_view.keypress(size, key)
+        assert self.controller.exit_popup.called
+
+    def test_keypress_command_key(self, mocker):
+        size = (200, 20)
+        mocker.patch(VIEWS + '.is_command_key', side_effect=(
+            lambda command, key: command == self.command
+        ))
+        self.pop_up_view.keypress(size, 'cmd_key')
+        assert self.controller.exit_popup.called
+
+    def test_keypress_navigation(self, mocker,
+                                 navigation_key_expected_key_pair):
+        key, expected_key = navigation_key_expected_key_pair
+        size = (200, 20)
+        # Patch `is_command_key` to not raise an 'Invalid Command' exception
+        # when its parameters are (self.command, key) as there is no
+        # self.command='COMMAND' command in keys.py.
+        mocker.patch(VIEWS + '.is_command_key', side_effect=(
+            lambda command, key:
+            False if command == self.command
+            else is_command_key(command, key)
+        ))
+        self.pop_up_view.keypress(size, key)
+        self.super_keypress.assert_called_once_with(size, expected_key)
+
+
 class TestHelpMenu:
     @pytest.fixture(autouse=True)
     def mock_external_classes(self, mocker, monkeypatch):

zulipterminal/ui_tools/views.py

@@ -754,10 +754,32 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
         return super().keypress(size, key)
 
 
-class HelpView(urwid.ListBox):
-    def __init__(self, controller: Any) -> None:
+class PopUpView(urwid.ListBox):
+    def __init__(self, controller: Any, widgets: List[Any],
+                 command: str) -> None:
         self.controller = controller
+        self.command = command
+        self.log = urwid.SimpleFocusListWalker(widgets)
+        super().__init__(self.log)
+
+    def keypress(self, size: urwid_Size, key: str) -> str:
+        if is_command_key('GO_BACK', key) or is_command_key(self.command, key):
+            self.controller.exit_popup()
+        elif is_command_key('GO_UP', key):
+            key = 'up'
+        elif is_command_key('GO_DOWN', key):
+            key = 'down'
+        elif is_command_key('SCROLL_UP', key):
+            key = 'page up'
+        elif is_command_key('SCROLL_DOWN', key):
+            key = 'page down'
+        elif is_command_key('GO_TO_BOTTOM', key):
+            key = 'end'
+        return super().keypress(size, key)
+
 
+class HelpView(PopUpView):
+    def __init__(self, controller: Any) -> None:
         widths = [(len(binding['help_text'])+4,
                    len(", ".join(binding['keys'])))
                   for binding in KEY_BINDINGS.values()]
@@ -786,26 +808,9 @@ def __init__(self, controller: Any) -> None:
                     )
                 )
 
-        self.log = urwid.SimpleFocusListWalker(help_menu_content)
-
-        self.height = len(self.log)
+        self.height = len(help_menu_content)
 
-        super().__init__(self.log)
-
-    def keypress(self, size: urwid_Size, key: str) -> str:
-        if is_command_key('GO_BACK', key) or is_command_key('HELP', key):
-            self.controller.exit_popup()
-        elif is_command_key('GO_UP', key):
-            key = 'up'
-        elif is_command_key('GO_DOWN', key):
-            key = 'down'
-        elif is_command_key('SCROLL_UP', key):
-            key = 'page up'
-        elif is_command_key('SCROLL_DOWN', key):
-            key = 'page down'
-        elif is_command_key('GO_TO_BOTTOM', key):
-            key = 'end'
-        return super().keypress(size, key)
+        super().__init__(controller, help_menu_content, 'HELP')
 
 
 class PopUpConfirmationView(urwid.Overlay):